Merge pull request #11336 from ctiller/ALL-the-things

Roll-up of threading changes

BUILD

@@ -521,8 +521,6 @@ grpc_cc_library(
         "src/core/lib/iomgr/wakeup_fd_nospecial.c",
         "src/core/lib/iomgr/wakeup_fd_pipe.c",
         "src/core/lib/iomgr/wakeup_fd_posix.c",
-        "src/core/lib/iomgr/workqueue_uv.c",
-        "src/core/lib/iomgr/workqueue_windows.c",
         "src/core/lib/json/json.c",
         "src/core/lib/json/json_reader.c",
         "src/core/lib/json/json_string.c",
@@ -640,9 +638,6 @@ grpc_cc_library(
         "src/core/lib/iomgr/wakeup_fd_cv.h",
         "src/core/lib/iomgr/wakeup_fd_pipe.h",
         "src/core/lib/iomgr/wakeup_fd_posix.h",
-        "src/core/lib/iomgr/workqueue.h",
-        "src/core/lib/iomgr/workqueue_uv.h",
-        "src/core/lib/iomgr/workqueue_windows.h",
         "src/core/lib/json/json.h",
         "src/core/lib/json/json_common.h",
         "src/core/lib/json/json_reader.h",

CMakeLists.txt

@@ -989,8 +989,6 @@ add_library(grpc
   src/core/lib/iomgr/wakeup_fd_nospecial.c
   src/core/lib/iomgr/wakeup_fd_pipe.c
   src/core/lib/iomgr/wakeup_fd_posix.c
-  src/core/lib/iomgr/workqueue_uv.c
-  src/core/lib/iomgr/workqueue_windows.c
   src/core/lib/json/json.c
   src/core/lib/json/json_reader.c
   src/core/lib/json/json_string.c
@@ -1330,8 +1328,6 @@ add_library(grpc_cronet
   src/core/lib/iomgr/wakeup_fd_nospecial.c
   src/core/lib/iomgr/wakeup_fd_pipe.c
   src/core/lib/iomgr/wakeup_fd_posix.c
-  src/core/lib/iomgr/workqueue_uv.c
-  src/core/lib/iomgr/workqueue_windows.c
   src/core/lib/json/json.c
   src/core/lib/json/json_reader.c
   src/core/lib/json/json_string.c
@@ -1649,8 +1645,6 @@ add_library(grpc_test_util
   src/core/lib/iomgr/wakeup_fd_nospecial.c
   src/core/lib/iomgr/wakeup_fd_pipe.c
   src/core/lib/iomgr/wakeup_fd_posix.c
-  src/core/lib/iomgr/workqueue_uv.c
-  src/core/lib/iomgr/workqueue_windows.c
   src/core/lib/json/json.c
   src/core/lib/json/json_reader.c
   src/core/lib/json/json_string.c
@@ -1913,8 +1907,6 @@ add_library(grpc_unsecure
   src/core/lib/iomgr/wakeup_fd_nospecial.c
   src/core/lib/iomgr/wakeup_fd_pipe.c
   src/core/lib/iomgr/wakeup_fd_posix.c
-  src/core/lib/iomgr/workqueue_uv.c
-  src/core/lib/iomgr/workqueue_windows.c
   src/core/lib/json/json.c
   src/core/lib/json/json_reader.c
   src/core/lib/json/json_string.c
@@ -2569,8 +2561,6 @@ add_library(grpc++_cronet
   src/core/lib/iomgr/wakeup_fd_nospecial.c
   src/core/lib/iomgr/wakeup_fd_pipe.c
   src/core/lib/iomgr/wakeup_fd_posix.c
-  src/core/lib/iomgr/workqueue_uv.c
-  src/core/lib/iomgr/workqueue_windows.c
   src/core/lib/json/json.c
   src/core/lib/json/json_reader.c
   src/core/lib/json/json_string.c

Makefile

@@ -2972,8 +2972,6 @@ LIBGRPC_SRC = \
     src/core/lib/iomgr/wakeup_fd_nospecial.c \
     src/core/lib/iomgr/wakeup_fd_pipe.c \
     src/core/lib/iomgr/wakeup_fd_posix.c \
-    src/core/lib/iomgr/workqueue_uv.c \
-    src/core/lib/iomgr/workqueue_windows.c \
     src/core/lib/json/json.c \
     src/core/lib/json/json_reader.c \
     src/core/lib/json/json_string.c \
@@ -3311,8 +3309,6 @@ LIBGRPC_CRONET_SRC = \
     src/core/lib/iomgr/wakeup_fd_nospecial.c \
     src/core/lib/iomgr/wakeup_fd_pipe.c \
     src/core/lib/iomgr/wakeup_fd_posix.c \
-    src/core/lib/iomgr/workqueue_uv.c \
-    src/core/lib/iomgr/workqueue_windows.c \
     src/core/lib/json/json.c \
     src/core/lib/json/json_reader.c \
     src/core/lib/json/json_string.c \
@@ -3629,8 +3625,6 @@ LIBGRPC_TEST_UTIL_SRC = \
     src/core/lib/iomgr/wakeup_fd_nospecial.c \
     src/core/lib/iomgr/wakeup_fd_pipe.c \
     src/core/lib/iomgr/wakeup_fd_posix.c \
-    src/core/lib/iomgr/workqueue_uv.c \
-    src/core/lib/iomgr/workqueue_windows.c \
     src/core/lib/json/json.c \
     src/core/lib/json/json_reader.c \
     src/core/lib/json/json_string.c \
@@ -3865,8 +3859,6 @@ LIBGRPC_UNSECURE_SRC = \
     src/core/lib/iomgr/wakeup_fd_nospecial.c \
     src/core/lib/iomgr/wakeup_fd_pipe.c \
     src/core/lib/iomgr/wakeup_fd_posix.c \
-    src/core/lib/iomgr/workqueue_uv.c \
-    src/core/lib/iomgr/workqueue_windows.c \
     src/core/lib/json/json.c \
     src/core/lib/json/json_reader.c \
     src/core/lib/json/json_string.c \
@@ -4507,8 +4499,6 @@ LIBGRPC++_CRONET_SRC = \
     src/core/lib/iomgr/wakeup_fd_nospecial.c \
     src/core/lib/iomgr/wakeup_fd_pipe.c \
     src/core/lib/iomgr/wakeup_fd_posix.c \
-    src/core/lib/iomgr/workqueue_uv.c \
-    src/core/lib/iomgr/workqueue_windows.c \
     src/core/lib/json/json.c \
     src/core/lib/json/json_reader.c \
     src/core/lib/json/json_string.c \

binding.gyp

@@ -720,8 +720,6 @@
         'src/core/lib/iomgr/wakeup_fd_nospecial.c',
         'src/core/lib/iomgr/wakeup_fd_pipe.c',
         'src/core/lib/iomgr/wakeup_fd_posix.c',
-        'src/core/lib/iomgr/workqueue_uv.c',
-        'src/core/lib/iomgr/workqueue_windows.c',
         'src/core/lib/json/json.c',
         'src/core/lib/json/json_reader.c',
         'src/core/lib/json/json_string.c',

build.yaml

@@ -254,9 +254,6 @@ filegroups:
   - src/core/lib/iomgr/wakeup_fd_cv.h
   - src/core/lib/iomgr/wakeup_fd_pipe.h
   - src/core/lib/iomgr/wakeup_fd_posix.h
-  - src/core/lib/iomgr/workqueue.h
-  - src/core/lib/iomgr/workqueue_uv.h
-  - src/core/lib/iomgr/workqueue_windows.h
   - src/core/lib/json/json.h
   - src/core/lib/json/json_common.h
   - src/core/lib/json/json_reader.h
@@ -375,8 +372,6 @@ filegroups:
   - src/core/lib/iomgr/wakeup_fd_nospecial.c
   - src/core/lib/iomgr/wakeup_fd_pipe.c
   - src/core/lib/iomgr/wakeup_fd_posix.c
-  - src/core/lib/iomgr/workqueue_uv.c
-  - src/core/lib/iomgr/workqueue_windows.c
   - src/core/lib/json/json.c
   - src/core/lib/json/json_reader.c
   - src/core/lib/json/json_string.c

config.m4

@@ -167,8 +167,6 @@ if test "$PHP_GRPC" != "no"; then
     src/core/lib/iomgr/wakeup_fd_nospecial.c \
     src/core/lib/iomgr/wakeup_fd_pipe.c \
     src/core/lib/iomgr/wakeup_fd_posix.c \
-    src/core/lib/iomgr/workqueue_uv.c \
-    src/core/lib/iomgr/workqueue_windows.c \
     src/core/lib/json/json.c \
     src/core/lib/json/json_reader.c \
     src/core/lib/json/json_string.c \

config.w32

@@ -144,8 +144,6 @@ if (PHP_GRPC != "no") {
     "src\\core\\lib\\iomgr\\wakeup_fd_nospecial.c " +
     "src\\core\\lib\\iomgr\\wakeup_fd_pipe.c " +
     "src\\core\\lib\\iomgr\\wakeup_fd_posix.c " +
-    "src\\core\\lib\\iomgr\\workqueue_uv.c " +
-    "src\\core\\lib\\iomgr\\workqueue_windows.c " +
     "src\\core\\lib\\json\\json.c " +
     "src\\core\\lib\\json\\json_reader.c " +
     "src\\core\\lib\\json\\json_string.c " +

gRPC-Core.podspec

@@ -318,9 +318,6 @@ Pod::Spec.new do |s|
                       'src/core/lib/iomgr/wakeup_fd_cv.h',
                       'src/core/lib/iomgr/wakeup_fd_pipe.h',
                       'src/core/lib/iomgr/wakeup_fd_posix.h',
-                      'src/core/lib/iomgr/workqueue.h',
-                      'src/core/lib/iomgr/workqueue_uv.h',
-                      'src/core/lib/iomgr/workqueue_windows.h',
                       'src/core/lib/json/json.h',
                       'src/core/lib/json/json_common.h',
                       'src/core/lib/json/json_reader.h',
@@ -546,8 +543,6 @@ Pod::Spec.new do |s|
                       'src/core/lib/iomgr/wakeup_fd_nospecial.c',
                       'src/core/lib/iomgr/wakeup_fd_pipe.c',
                       'src/core/lib/iomgr/wakeup_fd_posix.c',
-                      'src/core/lib/iomgr/workqueue_uv.c',
-                      'src/core/lib/iomgr/workqueue_windows.c',
                       'src/core/lib/json/json.c',
                       'src/core/lib/json/json_reader.c',
                       'src/core/lib/json/json_string.c',
@@ -807,9 +802,6 @@ Pod::Spec.new do |s|
                               'src/core/lib/iomgr/wakeup_fd_cv.h',
                               'src/core/lib/iomgr/wakeup_fd_pipe.h',
                               'src/core/lib/iomgr/wakeup_fd_posix.h',
-                              'src/core/lib/iomgr/workqueue.h',
-                              'src/core/lib/iomgr/workqueue_uv.h',
-                              'src/core/lib/iomgr/workqueue_windows.h',
                               'src/core/lib/json/json.h',
                               'src/core/lib/json/json_common.h',
                               'src/core/lib/json/json_reader.h',

grpc.gemspec

@@ -249,9 +249,6 @@ Gem::Specification.new do |s|
   s.files += %w( src/core/lib/iomgr/wakeup_fd_cv.h )
   s.files += %w( src/core/lib/iomgr/wakeup_fd_pipe.h )
   s.files += %w( src/core/lib/iomgr/wakeup_fd_posix.h )
-  s.files += %w( src/core/lib/iomgr/workqueue.h )
-  s.files += %w( src/core/lib/iomgr/workqueue_uv.h )
-  s.files += %w( src/core/lib/iomgr/workqueue_windows.h )
   s.files += %w( src/core/lib/json/json.h )
   s.files += %w( src/core/lib/json/json_common.h )
   s.files += %w( src/core/lib/json/json_reader.h )
@@ -477,8 +474,6 @@ Gem::Specification.new do |s|
   s.files += %w( src/core/lib/iomgr/wakeup_fd_nospecial.c )
   s.files += %w( src/core/lib/iomgr/wakeup_fd_pipe.c )
   s.files += %w( src/core/lib/iomgr/wakeup_fd_posix.c )
-  s.files += %w( src/core/lib/iomgr/workqueue_uv.c )
-  s.files += %w( src/core/lib/iomgr/workqueue_windows.c )
   s.files += %w( src/core/lib/json/json.c )
   s.files += %w( src/core/lib/json/json_reader.c )
   s.files += %w( src/core/lib/json/json_string.c )

package.xml

@@ -263,9 +263,6 @@
     <file baseinstalldir="/" name="src/core/lib/iomgr/wakeup_fd_cv.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/iomgr/wakeup_fd_pipe.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/iomgr/wakeup_fd_posix.h" role="src" />
-    <file baseinstalldir="/" name="src/core/lib/iomgr/workqueue.h" role="src" />
-    <file baseinstalldir="/" name="src/core/lib/iomgr/workqueue_uv.h" role="src" />
-    <file baseinstalldir="/" name="src/core/lib/iomgr/workqueue_windows.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/json/json.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/json/json_common.h" role="src" />
     <file baseinstalldir="/" name="src/core/lib/json/json_reader.h" role="src" />
@@ -491,8 +488,6 @@
     <file baseinstalldir="/" name="src/core/lib/iomgr/wakeup_fd_nospecial.c" role="src" />
     <file baseinstalldir="/" name="src/core/lib/iomgr/wakeup_fd_pipe.c" role="src" />
     <file baseinstalldir="/" name="src/core/lib/iomgr/wakeup_fd_posix.c" role="src" />
-    <file baseinstalldir="/" name="src/core/lib/iomgr/workqueue_uv.c" role="src" />
-    <file baseinstalldir="/" name="src/core/lib/iomgr/workqueue_windows.c" role="src" />
     <file baseinstalldir="/" name="src/core/lib/json/json.c" role="src" />
     <file baseinstalldir="/" name="src/core/lib/json/json_reader.c" role="src" />
     <file baseinstalldir="/" name="src/core/lib/json/json_string.c" role="src" />

src/core/ext/filters/client_channel/client_channel.c

@@ -276,7 +276,7 @@ static void watch_lb_policy_locked(grpc_exec_ctx *exec_ctx, channel_data *chand,
 
   w->chand = chand;
   grpc_closure_init(&w->on_changed, on_lb_policy_state_changed_locked, w,
-                    grpc_combiner_scheduler(chand->combiner, false));
+                    grpc_combiner_scheduler(chand->combiner));
   w->state = current_state;
   w->lb_policy = lb_policy;
   grpc_lb_policy_notify_on_state_change_locked(exec_ctx, lb_policy, &w->state,
@@ -637,7 +637,7 @@ static void cc_start_transport_op(grpc_exec_ctx *exec_ctx,
   grpc_closure_sched(
       exec_ctx,
       grpc_closure_init(&op->handler_private.closure, start_transport_op_locked,
-                        op, grpc_combiner_scheduler(chand->combiner, false)),
+                        op, grpc_combiner_scheduler(chand->combiner)),
       GRPC_ERROR_NONE);
 }
 
@@ -668,7 +668,7 @@ static grpc_error *cc_init_channel_elem(grpc_exec_ctx *exec_ctx,
   GPR_ASSERT(args->is_last);
   GPR_ASSERT(elem->filter == &grpc_client_channel_filter);
   // Initialize data members.
-  chand->combiner = grpc_combiner_create(NULL);
+  chand->combiner = grpc_combiner_create();
   gpr_mu_init(&chand->info_mu);
   gpr_mu_init(&chand->external_connectivity_watcher_list_mu);
 
@@ -679,7 +679,7 @@ static grpc_error *cc_init_channel_elem(grpc_exec_ctx *exec_ctx,
   chand->owning_stack = args->channel_stack;
   grpc_closure_init(&chand->on_resolver_result_changed,
                     on_resolver_result_changed_locked, chand,
-                    grpc_combiner_scheduler(chand->combiner, false));
+                    grpc_combiner_scheduler(chand->combiner));
   chand->interested_parties = grpc_pollset_set_create();
   grpc_connectivity_state_init(&chand->state_tracker, GRPC_CHANNEL_IDLE,
                                "client_channel");
@@ -738,9 +738,8 @@ static void cc_destroy_channel_elem(grpc_exec_ctx *exec_ctx,
   channel_data *chand = elem->channel_data;
   if (chand->resolver != NULL) {
     grpc_closure_sched(
-        exec_ctx,
-        grpc_closure_create(shutdown_resolver_locked, chand->resolver,
-                            grpc_combiner_scheduler(chand->combiner, false)),
+        exec_ctx, grpc_closure_create(shutdown_resolver_locked, chand->resolver,
+                                      grpc_combiner_scheduler(chand->combiner)),
         GRPC_ERROR_NONE);
   }
   if (chand->client_channel_factory != NULL) {
@@ -771,11 +770,6 @@ static void cc_destroy_channel_elem(grpc_exec_ctx *exec_ctx,
  * PER-CALL FUNCTIONS
  */
 
-#define GET_CALL(call_data) \
-  ((grpc_subchannel_call *)(gpr_atm_acq_load(&(call_data)->subchannel_call)))
-
-#define CANCELLED_CALL ((grpc_subchannel_call *)1)
-
 /** Call data.  Holds a pointer to grpc_subchannel_call and the
     associated machinery to create such a pointer.
     Handles queueing of stream ops until a call object is ready, waiting
@@ -796,11 +790,9 @@ typedef struct client_channel_call_data {
   grpc_server_retry_throttle_data *retry_throttle_data;
   method_parameters *method_params;
 
-  grpc_error *cancel_error;
-
-  /** either 0 for no call, 1 for cancelled, or a pointer to a
-      grpc_subchannel_call */
-  gpr_atm subchannel_call;
+  /** either 0 for no call, a pointer to a grpc_subchannel_call (if the lowest
+      bit is 0), or a pointer to an error (if the lowest bit is 1) */
+  gpr_atm subchannel_call_or_error;
   gpr_arena *arena;
 
   bool pick_pending;
@@ -822,10 +814,43 @@ typedef struct client_channel_call_data {
   grpc_closure *original_on_complete;
 } call_data;
 
+typedef struct {
+  grpc_subchannel_call *subchannel_call;
+  grpc_error *error;
+} call_or_error;
+
+static call_or_error get_call_or_error(call_data *p) {
+  gpr_atm c = gpr_atm_acq_load(&p->subchannel_call_or_error);
+  if (c == 0)
+    return (call_or_error){NULL, NULL};
+  else if (c & 1)
+    return (call_or_error){NULL, (grpc_error *)((c) & ~(gpr_atm)1)};
+  else
+    return (call_or_error){(grpc_subchannel_call *)c, NULL};
+}
+
+static bool set_call_or_error(call_data *p, call_or_error coe) {
+  // this should always be under a lock
+  call_or_error existing = get_call_or_error(p);
+  if (existing.error != GRPC_ERROR_NONE) {
+    GRPC_ERROR_UNREF(coe.error);
+    return false;
+  }
+  GPR_ASSERT(existing.subchannel_call == NULL);
+  if (coe.error != GRPC_ERROR_NONE) {
+    GPR_ASSERT(coe.subchannel_call == NULL);
+    gpr_atm_rel_store(&p->subchannel_call_or_error, 1 | (gpr_atm)coe.error);
+  } else {
+    GPR_ASSERT(coe.subchannel_call != NULL);
+    gpr_atm_rel_store(&p->subchannel_call_or_error,
+                      (gpr_atm)coe.subchannel_call);
+  }
+  return true;
+}
+
 grpc_subchannel_call *grpc_client_channel_get_subchannel_call(
     grpc_call_element *call_elem) {
-  grpc_subchannel_call *scc = GET_CALL((call_data *)call_elem->call_data);
-  return scc == CANCELLED_CALL ? NULL : scc;
+  return get_call_or_error(call_elem->call_data).subchannel_call;
 }
 
 static void add_waiting_locked(call_data *calld,
@@ -857,18 +882,18 @@ static void retry_waiting_locked(grpc_exec_ctx *exec_ctx, call_data *calld) {
     return;
   }
 
-  grpc_subchannel_call *call = GET_CALL(calld);
+  call_or_error call = get_call_or_error(calld);
   grpc_transport_stream_op_batch **ops = calld->waiting_ops;
   size_t nops = calld->waiting_ops_count;
-  if (call == CANCELLED_CALL) {
-    fail_locked(exec_ctx, calld, GRPC_ERROR_CANCELLED);
+  if (call.error != GRPC_ERROR_NONE) {
+    fail_locked(exec_ctx, calld, GRPC_ERROR_REF(call.error));
     return;
   }
   calld->waiting_ops = NULL;
   calld->waiting_ops_count = 0;
   calld->waiting_ops_capacity = 0;
   for (size_t i = 0; i < nops; i++) {
-    grpc_subchannel_call_process_op(exec_ctx, call, ops[i]);
+    grpc_subchannel_call_process_op(exec_ctx, call.subchannel_call, ops[i]);
   }
   gpr_free(ops);
 }
@@ -929,19 +954,23 @@ static void subchannel_ready_locked(grpc_exec_ctx *exec_ctx, void *arg,
   calld->pick_pending = false;
   grpc_polling_entity_del_from_pollset_set(exec_ctx, calld->pollent,
                                            chand->interested_parties);
+  call_or_error coe = get_call_or_error(calld);
   if (calld->connected_subchannel == NULL) {
-    gpr_atm_no_barrier_store(&calld->subchannel_call, (gpr_atm)CANCELLED_CALL);
-    fail_locked(exec_ctx, calld,
-                error == GRPC_ERROR_NONE
-                    ? GRPC_ERROR_CREATE_FROM_STATIC_STRING(
-                          "Call dropped by load balancing policy")
-                    : GRPC_ERROR_CREATE_REFERENCING_FROM_STATIC_STRING(
-                          "Failed to create subchannel", &error, 1));
-  } else if (GET_CALL(calld) == CANCELLED_CALL) {
+    grpc_error *failure =
+        error == GRPC_ERROR_NONE
+            ? GRPC_ERROR_CREATE_FROM_STATIC_STRING(
+                  "Call dropped by load balancing policy")
+            : GRPC_ERROR_CREATE_REFERENCING_FROM_STATIC_STRING(
+                  "Failed to create subchannel", &error, 1);
+    set_call_or_error(calld, (call_or_error){.error = GRPC_ERROR_REF(failure)});
+    fail_locked(exec_ctx, calld, failure);
+  } else if (coe.error != GRPC_ERROR_NONE) {
     /* already cancelled before subchannel became ready */
+    grpc_error *child_errors[] = {error, coe.error};
     grpc_error *cancellation_error =
         GRPC_ERROR_CREATE_REFERENCING_FROM_STATIC_STRING(
-            "Cancelled before creating subchannel", &error, 1);
+            "Cancelled before creating subchannel", child_errors,
+            GPR_ARRAY_SIZE(child_errors));
     /* if due to deadline, attach the deadline exceeded status to the error */
     if (gpr_time_cmp(calld->deadline, gpr_now(GPR_CLOCK_MONOTONIC)) < 0) {
       cancellation_error =
@@ -961,8 +990,8 @@ static void subchannel_ready_locked(grpc_exec_ctx *exec_ctx, void *arg,
         .context = calld->subchannel_call_context};
     grpc_error *new_error = grpc_connected_subchannel_create_call(
         exec_ctx, calld->connected_subchannel, &call_args, &subchannel_call);
-    gpr_atm_rel_store(&calld->subchannel_call,
-                      (gpr_atm)(uintptr_t)subchannel_call);
+    GPR_ASSERT(set_call_or_error(
+        calld, (call_or_error){.subchannel_call = subchannel_call}));
     if (new_error != GRPC_ERROR_NONE) {
       new_error = grpc_error_add_child(new_error, error);
       fail_locked(exec_ctx, calld, new_error);
@@ -975,8 +1004,9 @@ static void subchannel_ready_locked(grpc_exec_ctx *exec_ctx, void *arg,
 
 static char *cc_get_peer(grpc_exec_ctx *exec_ctx, grpc_call_element *elem) {
   call_data *calld = elem->call_data;
-  grpc_subchannel_call *subchannel_call = GET_CALL(calld);
-  if (subchannel_call == NULL || subchannel_call == CANCELLED_CALL) {
+  grpc_subchannel_call *subchannel_call =
+      get_call_or_error(calld).subchannel_call;
+  if (subchannel_call == NULL) {
     return NULL;
   } else {
     return grpc_subchannel_call_get_peer(exec_ctx, subchannel_call);
@@ -1118,7 +1148,7 @@ static bool pick_subchannel_locked(
     cpa->on_ready = on_ready;
     cpa->elem = elem;
     grpc_closure_init(&cpa->closure, continue_picking_locked, cpa,
-                      grpc_combiner_scheduler(chand->combiner, true));
+                      grpc_combiner_scheduler(chand->combiner));
     grpc_closure_list_append(&chand->waiting_for_config_closures, &cpa->closure,
                              GRPC_ERROR_NONE);
   } else {
@@ -1135,58 +1165,45 @@ static void start_transport_stream_op_batch_locked_inner(
     grpc_call_element *elem) {
   channel_data *chand = elem->channel_data;
   call_data *calld = elem->call_data;
-  grpc_subchannel_call *call;
 
   /* need to recheck that another thread hasn't set the call */
-  call = GET_CALL(calld);
-  if (call == CANCELLED_CALL) {
+  call_or_error coe = get_call_or_error(calld);
+  if (coe.error != GRPC_ERROR_NONE) {
     grpc_transport_stream_op_batch_finish_with_failure(
-        exec_ctx, op, GRPC_ERROR_REF(calld->cancel_error));
+        exec_ctx, op, GRPC_ERROR_REF(coe.error));
     /* early out */
     return;
   }
-  if (call != NULL) {
-    grpc_subchannel_call_process_op(exec_ctx, call, op);
+  if (coe.subchannel_call != NULL) {
+    grpc_subchannel_call_process_op(exec_ctx, coe.subchannel_call, op);
     /* early out */
     return;
   }
   /* if this is a cancellation, then we can raise our cancelled flag */
   if (op->cancel_stream) {
-    if (!gpr_atm_rel_cas(&calld->subchannel_call, 0,
-                         (gpr_atm)(uintptr_t)CANCELLED_CALL)) {
-      /* recurse to retry */
-      start_transport_stream_op_batch_locked_inner(exec_ctx, op, elem);
-      /* early out */
-      return;
+    grpc_error *error = op->payload->cancel_stream.cancel_error;
+    /* Stash a copy of cancel_error in our call data, so that we can use
+       it for subsequent operations.  This ensures that if the call is
+       cancelled before any ops are passed down (e.g., if the deadline
+       is in the past when the call starts), we can return the right
+       error to the caller when the first op does get passed down. */
+    set_call_or_error(calld, (call_or_error){.error = GRPC_ERROR_REF(error)});
+    if (calld->pick_pending) {
+      cancel_pick_locked(exec_ctx, elem, GRPC_ERROR_REF(error));
     } else {
-      /* Stash a copy of cancel_error in our call data, so that we can use
-         it for subsequent operations.  This ensures that if the call is
-         cancelled before any ops are passed down (e.g., if the deadline
-         is in the past when the call starts), we can return the right
-         error to the caller when the first op does get passed down. */
-      calld->cancel_error =
-          GRPC_ERROR_REF(op->payload->cancel_stream.cancel_error);
-      if (calld->pick_pending) {
-        cancel_pick_locked(
-            exec_ctx, elem,
-            GRPC_ERROR_REF(op->payload->cancel_stream.cancel_error));
-      } else {
-        fail_locked(exec_ctx, calld,
-                    GRPC_ERROR_REF(op->payload->cancel_stream.cancel_error));
-      }
-      grpc_transport_stream_op_batch_finish_with_failure(
-          exec_ctx, op,
-          GRPC_ERROR_REF(op->payload->cancel_stream.cancel_error));
-      /* early out */
-      return;
+      fail_locked(exec_ctx, calld, GRPC_ERROR_REF(error));
     }
+    grpc_transport_stream_op_batch_finish_with_failure(exec_ctx, op,
+                                                       GRPC_ERROR_REF(error));
+    /* early out */
+    return;
   }
   /* if we don't have a subchannel, try to get one */
   if (!calld->pick_pending && calld->connected_subchannel == NULL &&
       op->send_initial_metadata) {
     calld->pick_pending = true;
     grpc_closure_init(&calld->next_step, subchannel_ready_locked, elem,
-                      grpc_combiner_scheduler(chand->combiner, true));
+                      grpc_combiner_scheduler(chand->combiner));
     GRPC_CALL_STACK_REF(calld->owning_call, "pick_subchannel");
     /* If a subchannel is not available immediately, the polling entity from
        call_data should be provided to channel_data's interested_parties, so
@@ -1200,10 +1217,10 @@ static void start_transport_stream_op_batch_locked_inner(
       calld->pick_pending = false;
       GRPC_CALL_STACK_UNREF(exec_ctx, calld->owning_call, "pick_subchannel");
       if (calld->connected_subchannel == NULL) {
-        gpr_atm_no_barrier_store(&calld->subchannel_call,
-                                 (gpr_atm)CANCELLED_CALL);
         grpc_error *error = GRPC_ERROR_CREATE_FROM_STATIC_STRING(
             "Call dropped by load balancing policy");
+        set_call_or_error(calld,
+                          (call_or_error){.error = GRPC_ERROR_REF(error)});
         fail_locked(exec_ctx, calld, GRPC_ERROR_REF(error));
         grpc_transport_stream_op_batch_finish_with_failure(exec_ctx, op, error);
         return;  // Early out.
@@ -1225,8 +1242,8 @@ static void start_transport_stream_op_batch_locked_inner(
         .context = calld->subchannel_call_context};
     grpc_error *error = grpc_connected_subchannel_create_call(
         exec_ctx, calld->connected_subchannel, &call_args, &subchannel_call);
-    gpr_atm_rel_store(&calld->subchannel_call,
-                      (gpr_atm)(uintptr_t)subchannel_call);
+    GPR_ASSERT(set_call_or_error(
+        calld, (call_or_error){.subchannel_call = subchannel_call}));
     if (error != GRPC_ERROR_NONE) {
       fail_locked(exec_ctx, calld, GRPC_ERROR_REF(error));
       grpc_transport_stream_op_batch_finish_with_failure(exec_ctx, op, error);
@@ -1305,17 +1322,17 @@ static void cc_start_transport_stream_op_batch(
                                                                op);
   }
   /* try to (atomically) get the call */
-  grpc_subchannel_call *call = GET_CALL(calld);
+  call_or_error coe = get_call_or_error(calld);
   GPR_TIMER_BEGIN("cc_start_transport_stream_op_batch", 0);
-  if (call == CANCELLED_CALL) {
+  if (coe.error != GRPC_ERROR_NONE) {
     grpc_transport_stream_op_batch_finish_with_failure(
-        exec_ctx, op, GRPC_ERROR_REF(calld->cancel_error));
+        exec_ctx, op, GRPC_ERROR_REF(coe.error));
     GPR_TIMER_END("cc_start_transport_stream_op_batch", 0);
     /* early out */
     return;
   }
-  if (call != NULL) {
-    grpc_subchannel_call_process_op(exec_ctx, call, op);
+  if (coe.subchannel_call != NULL) {
+    grpc_subchannel_call_process_op(exec_ctx, coe.subchannel_call, op);
     GPR_TIMER_END("cc_start_transport_stream_op_batch", 0);
     /* early out */
     return;
@@ -1324,10 +1341,9 @@ static void cc_start_transport_stream_op_batch(
   GRPC_CALL_STACK_REF(calld->owning_call, "start_transport_stream_op_batch");
   op->handler_private.extra_arg = elem;
   grpc_closure_sched(
-      exec_ctx,
-      grpc_closure_init(&op->handler_private.closure,
-                        start_transport_stream_op_batch_locked, op,
-                        grpc_combiner_scheduler(chand->combiner, false)),
+      exec_ctx, grpc_closure_init(&op->handler_private.closure,
+                                  start_transport_stream_op_batch_locked, op,
+                                  grpc_combiner_scheduler(chand->combiner)),
       GRPC_ERROR_NONE);
   GPR_TIMER_END("cc_start_transport_stream_op_batch", 0);
 }
@@ -1364,12 +1380,14 @@ static void cc_destroy_call_elem(grpc_exec_ctx *exec_ctx,
   if (calld->method_params != NULL) {
     method_parameters_unref(calld->method_params);
   }
-  GRPC_ERROR_UNREF(calld->cancel_error);
-  grpc_subchannel_call *call = GET_CALL(calld);
-  if (call != NULL && call != CANCELLED_CALL) {
-    grpc_subchannel_call_set_cleanup_closure(call, then_schedule_closure);
+  call_or_error coe = get_call_or_error(calld);
+  GRPC_ERROR_UNREF(coe.error);
+  if (coe.subchannel_call != NULL) {
+    grpc_subchannel_call_set_cleanup_closure(coe.subchannel_call,
+                                             then_schedule_closure);
     then_schedule_closure = NULL;
-    GRPC_SUBCHANNEL_CALL_UNREF(exec_ctx, call, "client_channel_destroy_call");
+    GRPC_SUBCHANNEL_CALL_UNREF(exec_ctx, coe.subchannel_call,
+                               "client_channel_destroy_call");
   }
   GPR_ASSERT(!calld->pick_pending);
   GPR_ASSERT(calld->waiting_ops_count == 0);
@@ -1439,9 +1457,8 @@ grpc_connectivity_state grpc_client_channel_check_connectivity_state(
   if (out == GRPC_CHANNEL_IDLE && try_to_connect) {
     GRPC_CHANNEL_STACK_REF(chand->owning_stack, "try_to_connect");
     grpc_closure_sched(
-        exec_ctx,
-        grpc_closure_create(try_to_connect_locked, chand,
-                            grpc_combiner_scheduler(chand->combiner, false)),
+        exec_ctx, grpc_closure_create(try_to_connect_locked, chand,
+                                      grpc_combiner_scheduler(chand->combiner)),
         GRPC_ERROR_NONE);
   }
   return out;
@@ -1578,6 +1595,6 @@ void grpc_client_channel_watch_connectivity_state(
   grpc_closure_sched(
       exec_ctx,
       grpc_closure_init(&w->my_closure, watch_connectivity_state_locked, w,
-                        grpc_combiner_scheduler(chand->combiner, true)),
+                        grpc_combiner_scheduler(chand->combiner)),
       GRPC_ERROR_NONE);
 }

src/core/ext/filters/client_channel/lb_policy.c

@@ -74,11 +74,10 @@ void grpc_lb_policy_unref(grpc_exec_ctx *exec_ctx,
   gpr_atm mask = ~(gpr_atm)((1 << WEAK_REF_BITS) - 1);
   gpr_atm check = 1 << WEAK_REF_BITS;
   if ((old_val & mask) == check) {
-    grpc_closure_sched(
-        exec_ctx,
-        grpc_closure_create(shutdown_locked, policy,
-                            grpc_combiner_scheduler(policy->combiner, false)),
-        GRPC_ERROR_NONE);
+    grpc_closure_sched(exec_ctx, grpc_closure_create(
+                                     shutdown_locked, policy,
+                                     grpc_combiner_scheduler(policy->combiner)),
+                       GRPC_ERROR_NONE);
   } else {
     grpc_lb_policy_weak_unref(exec_ctx,
                               policy REF_FUNC_PASS_ARGS("strong-unref"));

src/core/ext/filters/client_channel/lb_policy/grpclb/grpclb.c

@@ -741,7 +741,7 @@ static void create_rr_locked(grpc_exec_ctx *exec_ctx, glb_lb_policy *glb_policy,
       gpr_zalloc(sizeof(rr_connectivity_data));
   grpc_closure_init(&rr_connectivity->on_change,
                     glb_rr_connectivity_changed_locked, rr_connectivity,
-                    grpc_combiner_scheduler(glb_policy->base.combiner, false));
+                    grpc_combiner_scheduler(glb_policy->base.combiner));
   rr_connectivity->glb_policy = glb_policy;
   rr_connectivity->state = rr_state;
 
@@ -1006,7 +1006,7 @@ static grpc_lb_policy *glb_create(grpc_exec_ctx *exec_ctx,
 
   grpc_closure_init(&glb_policy->lb_channel_on_connectivity_changed,
                     glb_lb_channel_on_connectivity_changed_cb, glb_policy,
-                    grpc_combiner_scheduler(args->combiner, false));
+                    grpc_combiner_scheduler(args->combiner));
   grpc_lb_policy_init(&glb_policy->base, &glb_lb_policy_vtable, args->combiner);
   grpc_connectivity_state_init(&glb_policy->state_tracker, GRPC_CHANNEL_IDLE,
                                "grpclb");
@@ -1252,7 +1252,7 @@ static void schedule_next_client_load_report(grpc_exec_ctx *exec_ctx,
       gpr_time_add(now, glb_policy->client_stats_report_interval);
   grpc_closure_init(&glb_policy->client_load_report_closure,
                     send_client_load_report_locked, glb_policy,
-                    grpc_combiner_scheduler(glb_policy->base.combiner, false));
+                    grpc_combiner_scheduler(glb_policy->base.combiner));
   grpc_timer_init(exec_ctx, &glb_policy->client_load_report_timer,
                   next_client_load_report_time,
                   &glb_policy->client_load_report_closure, now);
@@ -1280,7 +1280,7 @@ static void do_send_client_load_report_locked(grpc_exec_ctx *exec_ctx,
   op.data.send_message.send_message = glb_policy->client_load_report_payload;
   grpc_closure_init(&glb_policy->client_load_report_closure,
                     client_load_report_done_locked, glb_policy,
-                    grpc_combiner_scheduler(glb_policy->base.combiner, false));
+                    grpc_combiner_scheduler(glb_policy->base.combiner));
   grpc_call_error call_error = grpc_call_start_batch_and_execute(
       exec_ctx, glb_policy->lb_call, &op, 1,
       &glb_policy->client_load_report_closure);
@@ -1386,13 +1386,13 @@ static void lb_call_init_locked(grpc_exec_ctx *exec_ctx,
 
   grpc_closure_init(&glb_policy->lb_on_sent_initial_request,
                     lb_on_sent_initial_request_locked, glb_policy,
-                    grpc_combiner_scheduler(glb_policy->base.combiner, false));
+                    grpc_combiner_scheduler(glb_policy->base.combiner));
   grpc_closure_init(&glb_policy->lb_on_server_status_received,
                     lb_on_server_status_received_locked, glb_policy,
-                    grpc_combiner_scheduler(glb_policy->base.combiner, false));
+                    grpc_combiner_scheduler(glb_policy->base.combiner));
   grpc_closure_init(&glb_policy->lb_on_response_received,
                     lb_on_response_received_locked, glb_policy,
-                    grpc_combiner_scheduler(glb_policy->base.combiner, false));
+                    grpc_combiner_scheduler(glb_policy->base.combiner));
 
   gpr_backoff_init(&glb_policy->lb_call_backoff_state,
                    GRPC_GRPCLB_INITIAL_CONNECT_BACKOFF_SECONDS,
@@ -1693,9 +1693,9 @@ static void lb_on_server_status_received_locked(grpc_exec_ctx *exec_ctx,
       }
     }
     GRPC_LB_POLICY_WEAK_REF(&glb_policy->base, "grpclb_retry_timer");
-    grpc_closure_init(
-        &glb_policy->lb_on_call_retry, lb_call_on_retry_timer_locked,
-        glb_policy, grpc_combiner_scheduler(glb_policy->base.combiner, false));
+    grpc_closure_init(&glb_policy->lb_on_call_retry,
+                      lb_call_on_retry_timer_locked, glb_policy,
+                      grpc_combiner_scheduler(glb_policy->base.combiner));
     glb_policy->retry_timer_active = true;
     grpc_timer_init(exec_ctx, &glb_policy->lb_call_retry_timer, next_try,
                     &glb_policy->lb_on_call_retry, now);

src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.c

@@ -655,7 +655,7 @@ static grpc_lb_policy *create_pick_first(grpc_exec_ctx *exec_ctx,
   pf_update_locked(exec_ctx, &p->base, args);
   grpc_lb_policy_init(&p->base, &pick_first_lb_policy_vtable, args->combiner);
   grpc_closure_init(&p->connectivity_changed, pf_connectivity_changed_locked, p,
-                    grpc_combiner_scheduler(args->combiner, false));
+                    grpc_combiner_scheduler(args->combiner));
   return &p->base;
 }
 

src/core/ext/filters/client_channel/lb_policy/round_robin/round_robin.c

@@ -749,7 +749,7 @@ static void rr_update_locked(grpc_exec_ctx *exec_ctx, grpc_lb_policy *policy,
     sd->subchannel = subchannel;
     grpc_closure_init(&sd->connectivity_changed_closure,
                       rr_connectivity_changed_locked, sd,
-                      grpc_combiner_scheduler(args->combiner, false));
+                      grpc_combiner_scheduler(args->combiner));
     /* use some sentinel value outside of the range of
      * grpc_connectivity_state to signal an undefined previous state. We
      * won't be referring to this value again and it'll be overwritten after

src/core/ext/filters/client_channel/resolver/dns/c_ares/dns_resolver_ares.c

@@ -268,10 +268,10 @@ static grpc_resolver *dns_ares_create(grpc_exec_ctx *exec_ctx,
                    GRPC_DNS_RECONNECT_MAX_BACKOFF_SECONDS * 1000);
   grpc_closure_init(&r->dns_ares_on_retry_timer_locked,
                     dns_ares_on_retry_timer_locked, r,
-                    grpc_combiner_scheduler(r->base.combiner, false));
+                    grpc_combiner_scheduler(r->base.combiner));
   grpc_closure_init(&r->dns_ares_on_resolved_locked,
                     dns_ares_on_resolved_locked, r,
-                    grpc_combiner_scheduler(r->base.combiner, false));
+                    grpc_combiner_scheduler(r->base.combiner));
   return &r->base;
 }
 

src/core/ext/filters/client_channel/resolver/dns/native/dns_resolver.c

@@ -179,7 +179,7 @@ static void dns_on_resolved_locked(grpc_exec_ctx *exec_ctx, void *arg,
       gpr_log(GPR_DEBUG, "retrying immediately");
     }
     grpc_closure_init(&r->on_retry, dns_on_retry_timer_locked, r,
-                      grpc_combiner_scheduler(r->base.combiner, false));
+                      grpc_combiner_scheduler(r->base.combiner));
     grpc_timer_init(exec_ctx, &r->retry_timer, next_try, &r->on_retry, now);
   }
   if (r->resolved_result != NULL) {
@@ -201,7 +201,7 @@ static void dns_start_resolving_locked(grpc_exec_ctx *exec_ctx,
   grpc_resolve_address(
       exec_ctx, r->name_to_resolve, r->default_port, r->interested_parties,
       grpc_closure_create(dns_on_resolved_locked, r,
-                          grpc_combiner_scheduler(r->base.combiner, false)),
+                          grpc_combiner_scheduler(r->base.combiner)),
       &r->addresses);
 }
 

src/core/ext/filters/client_channel/resolver/fake/fake_resolver.c

@@ -158,10 +158,9 @@ void grpc_fake_resolver_response_generator_set_response(
   GPR_ASSERT(generator->resolver != NULL);
   generator->next_response = grpc_channel_args_copy(next_response);
   grpc_closure_sched(
-      exec_ctx,
-      grpc_closure_create(
-          set_response_cb, generator,
-          grpc_combiner_scheduler(generator->resolver->base.combiner, false)),
+      exec_ctx, grpc_closure_create(set_response_cb, generator,
+                                    grpc_combiner_scheduler(
+                                        generator->resolver->base.combiner)),
       GRPC_ERROR_NONE);
 }
 

src/core/ext/transport/chttp2/transport/chttp2_transport.c

@@ -35,7 +35,6 @@
 #include "src/core/lib/channel/channel_args.h"
 #include "src/core/lib/http/parser.h"
 #include "src/core/lib/iomgr/timer.h"
-#include "src/core/lib/iomgr/workqueue.h"
 #include "src/core/lib/profiling/timers.h"
 #include "src/core/lib/slice/slice_internal.h"
 #include "src/core/lib/slice/slice_string_helpers.h"
@@ -252,7 +251,7 @@ static void init_transport(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
   t->ep = ep;
   /* one ref is for destroy */
   gpr_ref_init(&t->refs, 1);
-  t->combiner = grpc_combiner_create(grpc_endpoint_get_workqueue(ep));
+  t->combiner = grpc_combiner_create();
   t->peer_string = grpc_endpoint_get_peer(ep);
   t->endpoint_reading = 1;
   t->next_stream_id = is_client ? 1 : 2;
@@ -273,29 +272,29 @@ static void init_transport(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
   grpc_closure_init(&t->write_action, write_action, t,
                     grpc_schedule_on_exec_ctx);
   grpc_closure_init(&t->read_action_locked, read_action_locked, t,
-                    grpc_combiner_scheduler(t->combiner, false));
+                    grpc_combiner_scheduler(t->combiner));
   grpc_closure_init(&t->benign_reclaimer_locked, benign_reclaimer_locked, t,
-                    grpc_combiner_scheduler(t->combiner, false));
+                    grpc_combiner_scheduler(t->combiner));
   grpc_closure_init(&t->destructive_reclaimer_locked,
                     destructive_reclaimer_locked, t,
-                    grpc_combiner_scheduler(t->combiner, false));
+                    grpc_combiner_scheduler(t->combiner));
   grpc_closure_init(&t->retry_initiate_ping_locked, retry_initiate_ping_locked,
-                    t, grpc_combiner_scheduler(t->combiner, false));
+                    t, grpc_combiner_scheduler(t->combiner));
   grpc_closure_init(&t->start_bdp_ping_locked, start_bdp_ping_locked, t,
-                    grpc_combiner_scheduler(t->combiner, false));
+                    grpc_combiner_scheduler(t->combiner));
   grpc_closure_init(&t->finish_bdp_ping_locked, finish_bdp_ping_locked, t,
-                    grpc_combiner_scheduler(t->combiner, false));
+                    grpc_combiner_scheduler(t->combiner));
   grpc_closure_init(&t->init_keepalive_ping_locked, init_keepalive_ping_locked,
-                    t, grpc_combiner_scheduler(t->combiner, false));
+                    t, grpc_combiner_scheduler(t->combiner));
   grpc_closure_init(&t->start_keepalive_ping_locked,
                     start_keepalive_ping_locked, t,
-                    grpc_combiner_scheduler(t->combiner, false));
+                    grpc_combiner_scheduler(t->combiner));
   grpc_closure_init(&t->finish_keepalive_ping_locked,
                     finish_keepalive_ping_locked, t,
-                    grpc_combiner_scheduler(t->combiner, false));
+                    grpc_combiner_scheduler(t->combiner));
   grpc_closure_init(&t->keepalive_watchdog_fired_locked,
                     keepalive_watchdog_fired_locked, t,
-                    grpc_combiner_scheduler(t->combiner, false));
+                    grpc_combiner_scheduler(t->combiner));
 
   grpc_bdp_estimator_init(&t->bdp_estimator, t->peer_string);
   t->last_pid_update = gpr_now(GPR_CLOCK_MONOTONIC);
@@ -338,7 +337,7 @@ static void init_transport(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
   if (is_client) {
     grpc_slice_buffer_add(&t->outbuf, grpc_slice_from_copied_string(
                                           GRPC_CHTTP2_CLIENT_CONNECT_STRING));
-    grpc_chttp2_initiate_write(exec_ctx, t, false, "initial_write");
+    grpc_chttp2_initiate_write(exec_ctx, t, "initial_write");
   }
 
   /* configure http2 the way we like it */
@@ -550,7 +549,7 @@ static void init_transport(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
     t->keepalive_state = GRPC_CHTTP2_KEEPALIVE_STATE_DISABLED;
   }
 
-  grpc_chttp2_initiate_write(exec_ctx, t, false, "init");
+  grpc_chttp2_initiate_write(exec_ctx, t, "init");
   post_benign_reclaimer(exec_ctx, t);
 }
 
@@ -568,9 +567,9 @@ static void destroy_transport_locked(grpc_exec_ctx *exec_ctx, void *tp,
 
 static void destroy_transport(grpc_exec_ctx *exec_ctx, grpc_transport *gt) {
   grpc_chttp2_transport *t = (grpc_chttp2_transport *)gt;
-  grpc_closure_sched(exec_ctx, grpc_closure_create(
-                                   destroy_transport_locked, t,
-                                   grpc_combiner_scheduler(t->combiner, false)),
+  grpc_closure_sched(exec_ctx,
+                     grpc_closure_create(destroy_transport_locked, t,
+                                         grpc_combiner_scheduler(t->combiner)),
                      GRPC_ERROR_NONE);
 }
 
@@ -663,7 +662,7 @@ static int init_stream(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
   grpc_slice_buffer_init(&s->frame_storage);
   s->pending_byte_stream = false;
   grpc_closure_init(&s->reset_byte_stream, reset_byte_stream, s,
-                    grpc_combiner_scheduler(t->combiner, false));
+                    grpc_combiner_scheduler(t->combiner));
 
   GRPC_CHTTP2_REF_TRANSPORT(t, "stream");
 
@@ -747,7 +746,7 @@ static void destroy_stream(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
   s->destroy_stream_arg = then_schedule_closure;
   grpc_closure_sched(
       exec_ctx, grpc_closure_init(&s->destroy_stream, destroy_stream_locked, s,
-                                  grpc_combiner_scheduler(t->combiner, false)),
+                                  grpc_combiner_scheduler(t->combiner)),
       GRPC_ERROR_NONE);
   GPR_TIMER_END("destroy_stream", 0);
 }
@@ -785,8 +784,6 @@ static const char *write_state_name(grpc_chttp2_write_state st) {
       return "WRITING";
     case GRPC_CHTTP2_WRITE_STATE_WRITING_WITH_MORE:
       return "WRITING+MORE";
-    case GRPC_CHTTP2_WRITE_STATE_WRITING_WITH_MORE_AND_COVERED_BY_POLLER:
-      return "WRITING+MORE+COVERED";
   }
   GPR_UNREACHABLE_CODE(return "UNKNOWN");
 }
@@ -809,8 +806,7 @@ static void set_write_state(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
 }
 
 void grpc_chttp2_initiate_write(grpc_exec_ctx *exec_ctx,
-                                grpc_chttp2_transport *t,
-                                bool covered_by_poller, const char *reason) {
+                                grpc_chttp2_transport *t, const char *reason) {
   GPR_TIMER_BEGIN("grpc_chttp2_initiate_write", 0);
 
   switch (t->write_state) {
@@ -819,28 +815,16 @@ void grpc_chttp2_initiate_write(grpc_exec_ctx *exec_ctx,
       GRPC_CHTTP2_REF_TRANSPORT(t, "writing");
       grpc_closure_sched(
           exec_ctx,
-          grpc_closure_init(
-              &t->write_action_begin_locked, write_action_begin_locked, t,
-              grpc_combiner_finally_scheduler(t->combiner, covered_by_poller)),
+          grpc_closure_init(&t->write_action_begin_locked,
+                            write_action_begin_locked, t,
+                            grpc_combiner_finally_scheduler(t->combiner)),
           GRPC_ERROR_NONE);
       break;
     case GRPC_CHTTP2_WRITE_STATE_WRITING:
-      set_write_state(
-          exec_ctx, t,
-          covered_by_poller
-              ? GRPC_CHTTP2_WRITE_STATE_WRITING_WITH_MORE_AND_COVERED_BY_POLLER
-              : GRPC_CHTTP2_WRITE_STATE_WRITING_WITH_MORE,
-          reason);
+      set_write_state(exec_ctx, t, GRPC_CHTTP2_WRITE_STATE_WRITING_WITH_MORE,
+                      reason);
       break;
     case GRPC_CHTTP2_WRITE_STATE_WRITING_WITH_MORE:
-      if (covered_by_poller) {
-        set_write_state(
-            exec_ctx, t,
-            GRPC_CHTTP2_WRITE_STATE_WRITING_WITH_MORE_AND_COVERED_BY_POLLER,
-            reason);
-      }
-      break;
-    case GRPC_CHTTP2_WRITE_STATE_WRITING_WITH_MORE_AND_COVERED_BY_POLLER:
       break;
   }
   GPR_TIMER_END("grpc_chttp2_initiate_write", 0);
@@ -856,10 +840,10 @@ void grpc_chttp2_become_writable(
     case GRPC_CHTTP2_STREAM_WRITE_PIGGYBACK:
       break;
     case GRPC_CHTTP2_STREAM_WRITE_INITIATE_COVERED:
-      grpc_chttp2_initiate_write(exec_ctx, t, true, reason);
+      grpc_chttp2_initiate_write(exec_ctx, t, reason);
       break;
     case GRPC_CHTTP2_STREAM_WRITE_INITIATE_UNCOVERED:
-      grpc_chttp2_initiate_write(exec_ctx, t, false, reason);
+      grpc_chttp2_initiate_write(exec_ctx, t, reason);
       break;
   }
 }
@@ -896,7 +880,7 @@ static void write_action(grpc_exec_ctx *exec_ctx, void *gt, grpc_error *error) {
   grpc_endpoint_write(
       exec_ctx, t->ep, &t->outbuf,
       grpc_closure_init(&t->write_action_end_locked, write_action_end_locked, t,
-                        grpc_combiner_scheduler(t->combiner, false)));
+                        grpc_combiner_scheduler(t->combiner)));
   GPR_TIMER_END("write_action", 0);
 }
 
@@ -930,23 +914,11 @@ static void write_action_end_locked(grpc_exec_ctx *exec_ctx, void *tp,
       set_write_state(exec_ctx, t, GRPC_CHTTP2_WRITE_STATE_WRITING,
                       "continue writing [!covered]");
       GRPC_CHTTP2_REF_TRANSPORT(t, "writing");
-      grpc_closure_run(
-          exec_ctx,
-          grpc_closure_init(
-              &t->write_action_begin_locked, write_action_begin_locked, t,
-              grpc_combiner_finally_scheduler(t->combiner, false)),
-          GRPC_ERROR_NONE);
-      break;
-    case GRPC_CHTTP2_WRITE_STATE_WRITING_WITH_MORE_AND_COVERED_BY_POLLER:
-      GPR_TIMER_MARK("state=writing_stale_with_poller", 0);
-      set_write_state(exec_ctx, t, GRPC_CHTTP2_WRITE_STATE_WRITING,
-                      "continue writing [covered]");
-      GRPC_CHTTP2_REF_TRANSPORT(t, "writing");
       grpc_closure_run(
           exec_ctx,
           grpc_closure_init(&t->write_action_begin_locked,
                             write_action_begin_locked, t,
-                            grpc_combiner_finally_scheduler(t->combiner, true)),
+                            grpc_combiner_finally_scheduler(t->combiner)),
           GRPC_ERROR_NONE);
       break;
   }
@@ -969,7 +941,7 @@ static void push_setting(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
   if (use_value != t->settings[GRPC_LOCAL_SETTINGS][id]) {
     t->settings[GRPC_LOCAL_SETTINGS][id] = use_value;
     t->dirtied_local_settings = 1;
-    grpc_chttp2_initiate_write(exec_ctx, t, false, "push_setting");
+    grpc_chttp2_initiate_write(exec_ctx, t, "push_setting");
   }
 }
 
@@ -1365,7 +1337,6 @@ static void perform_stream_op_locked(grpc_exec_ctx *exec_ctx, void *stream_op,
       s->next_message_end_offset = s->flow_controlled_bytes_written +
                                    (int64_t)s->flow_controlled_buffer.length +
                                    (int64_t)len;
-      s->complete_fetch_covered_by_poller = op->covered_by_poller;
       if (flags & GRPC_WRITE_BUFFER_HINT) {
         s->next_message_end_offset -= t->write_buffer_size;
         s->write_buffering = true;
@@ -1487,9 +1458,8 @@ static void perform_stream_op(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
   GRPC_CHTTP2_STREAM_REF(s, "perform_stream_op");
   grpc_closure_sched(
       exec_ctx,
-      grpc_closure_init(
-          &op->handler_private.closure, perform_stream_op_locked, op,
-          grpc_combiner_scheduler(t->combiner, op->covered_by_poller)),
+      grpc_closure_init(&op->handler_private.closure, perform_stream_op_locked,
+                        op, grpc_combiner_scheduler(t->combiner)),
       GRPC_ERROR_NONE);
   GPR_TIMER_END("perform_stream_op", 0);
 }
@@ -1516,7 +1486,7 @@ static void send_ping_locked(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
                            GRPC_ERROR_NONE);
   if (grpc_closure_list_append(&pq->lists[GRPC_CHTTP2_PCL_NEXT], on_ack,
                                GRPC_ERROR_NONE)) {
-    grpc_chttp2_initiate_write(exec_ctx, t, false, "send_ping");
+    grpc_chttp2_initiate_write(exec_ctx, t, "send_ping");
   }
 }
 
@@ -1524,7 +1494,7 @@ static void retry_initiate_ping_locked(grpc_exec_ctx *exec_ctx, void *tp,
                                        grpc_error *error) {
   grpc_chttp2_transport *t = tp;
   t->ping_state.is_delayed_ping_timer_set = false;
-  grpc_chttp2_initiate_write(exec_ctx, t, false, "retry_send_ping");
+  grpc_chttp2_initiate_write(exec_ctx, t, "retry_send_ping");
 }
 
 void grpc_chttp2_ack_ping(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
@@ -1539,7 +1509,7 @@ void grpc_chttp2_ack_ping(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
   }
   grpc_closure_list_sched(exec_ctx, &pq->lists[GRPC_CHTTP2_PCL_INFLIGHT]);
   if (!grpc_closure_list_empty(pq->lists[GRPC_CHTTP2_PCL_NEXT])) {
-    grpc_chttp2_initiate_write(exec_ctx, t, false, "continue_pings");
+    grpc_chttp2_initiate_write(exec_ctx, t, "continue_pings");
   }
 }
 
@@ -1552,7 +1522,7 @@ static void send_goaway(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
                         &slice, &http_error);
   grpc_chttp2_goaway_append(t->last_new_stream_id, (uint32_t)http_error,
                             grpc_slice_ref_internal(slice), &t->qbuf);
-  grpc_chttp2_initiate_write(exec_ctx, t, false, "goaway_sent");
+  grpc_chttp2_initiate_write(exec_ctx, t, "goaway_sent");
   GRPC_ERROR_UNREF(error);
 }
 
@@ -1578,12 +1548,6 @@ static void perform_transport_op_locked(grpc_exec_ctx *exec_ctx,
   grpc_chttp2_transport *t = op->handler_private.extra_arg;
   grpc_error *close_transport = op->disconnect_with_error;
 
-  if (op->on_connectivity_state_change != NULL) {
-    grpc_connectivity_state_notify_on_state_change(
-        exec_ctx, &t->channel_callback.state_tracker, op->connectivity_state,
-        op->on_connectivity_state_change);
-  }
-
   if (op->goaway_error) {
     send_goaway(exec_ctx, t, op->goaway_error);
   }
@@ -1607,6 +1571,12 @@ static void perform_transport_op_locked(grpc_exec_ctx *exec_ctx,
                      op->send_ping);
   }
 
+  if (op->on_connectivity_state_change != NULL) {
+    grpc_connectivity_state_notify_on_state_change(
+        exec_ctx, &t->channel_callback.state_tracker, op->connectivity_state,
+        op->on_connectivity_state_change);
+  }
+
   if (close_transport != GRPC_ERROR_NONE) {
     close_transport_locked(exec_ctx, t, close_transport);
   }
@@ -1623,11 +1593,11 @@ static void perform_transport_op(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
   gpr_free(msg);
   op->handler_private.extra_arg = gt;
   GRPC_CHTTP2_REF_TRANSPORT(t, "transport_op");
-  grpc_closure_sched(
-      exec_ctx, grpc_closure_init(&op->handler_private.closure,
-                                  perform_transport_op_locked, op,
-                                  grpc_combiner_scheduler(t->combiner, false)),
-      GRPC_ERROR_NONE);
+  grpc_closure_sched(exec_ctx,
+                     grpc_closure_init(&op->handler_private.closure,
+                                       perform_transport_op_locked, op,
+                                       grpc_combiner_scheduler(t->combiner)),
+                     GRPC_ERROR_NONE);
 }
 
 /*******************************************************************************
@@ -1782,7 +1752,7 @@ void grpc_chttp2_cancel_stream(grpc_exec_ctx *exec_ctx,
       grpc_slice_buffer_add(
           &t->qbuf, grpc_chttp2_rst_stream_create(s->id, (uint32_t)http_error,
                                                   &s->stats.outgoing));
-      grpc_chttp2_initiate_write(exec_ctx, t, false, "rst_stream");
+      grpc_chttp2_initiate_write(exec_ctx, t, "rst_stream");
     }
   }
   if (due_to_error != GRPC_ERROR_NONE && !s->seen_error) {
@@ -2095,7 +2065,7 @@ static void close_from_api(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
                                               &s->stats.outgoing));
 
   grpc_chttp2_mark_stream_closed(exec_ctx, t, s, 1, 1, error);
-  grpc_chttp2_initiate_write(exec_ctx, t, false, "close_from_api");
+  grpc_chttp2_initiate_write(exec_ctx, t, "close_from_api");
 }
 
 typedef struct {
@@ -2626,9 +2596,9 @@ static bool incoming_byte_stream_next(grpc_exec_ctx *exec_ctx,
     bs->next_action.on_complete = on_complete;
     grpc_closure_sched(
         exec_ctx,
-        grpc_closure_init(
-            &bs->next_action.closure, incoming_byte_stream_next_locked, bs,
-            grpc_combiner_scheduler(bs->transport->combiner, false)),
+        grpc_closure_init(&bs->next_action.closure,
+                          incoming_byte_stream_next_locked, bs,
+                          grpc_combiner_scheduler(bs->transport->combiner)),
         GRPC_ERROR_NONE);
     GPR_TIMER_END("incoming_byte_stream_next", 0);
     return false;
@@ -2683,10 +2653,9 @@ static void incoming_byte_stream_destroy(grpc_exec_ctx *exec_ctx,
   grpc_chttp2_incoming_byte_stream *bs =
       (grpc_chttp2_incoming_byte_stream *)byte_stream;
   grpc_closure_sched(
-      exec_ctx,
-      grpc_closure_init(
-          &bs->destroy_action, incoming_byte_stream_destroy_locked, bs,
-          grpc_combiner_scheduler(bs->transport->combiner, false)),
+      exec_ctx, grpc_closure_init(
+                    &bs->destroy_action, incoming_byte_stream_destroy_locked,
+                    bs, grpc_combiner_scheduler(bs->transport->combiner)),
       GRPC_ERROR_NONE);
   GPR_TIMER_END("incoming_byte_stream_destroy", 0);
 }

src/core/ext/transport/chttp2/transport/frame_ping.c

@@ -117,7 +117,7 @@ grpc_error *grpc_chttp2_ping_parser_parse(grpc_exec_ctx *exec_ctx, void *parser,
               t->ping_acks, t->ping_ack_capacity * sizeof(*t->ping_acks));
         }
         t->ping_acks[t->ping_ack_count++] = p->opaque_8bytes;
-        grpc_chttp2_initiate_write(exec_ctx, t, false, "ping response");
+        grpc_chttp2_initiate_write(exec_ctx, t, "ping response");
       }
     }
   }

src/core/ext/transport/chttp2/transport/frame_window_update.c

@@ -109,8 +109,7 @@ grpc_error *grpc_chttp2_window_update_parser_parse(
                                         received_update);
       bool is_zero = t->outgoing_window <= 0;
       if (was_zero && !is_zero) {
-        grpc_chttp2_initiate_write(exec_ctx, t, false,
-                                   "new_global_flow_control");
+        grpc_chttp2_initiate_write(exec_ctx, t, "new_global_flow_control");
       }
     }
   }

src/core/ext/transport/chttp2/transport/hpack_parser.c

@@ -1649,7 +1649,7 @@ static void force_client_rst_stream(grpc_exec_ctx *exec_ctx, void *sp,
     grpc_slice_buffer_add(
         &t->qbuf, grpc_chttp2_rst_stream_create(s->id, GRPC_HTTP2_NO_ERROR,
                                                 &s->stats.outgoing));
-    grpc_chttp2_initiate_write(exec_ctx, t, false, "force_rst_stream");
+    grpc_chttp2_initiate_write(exec_ctx, t, "force_rst_stream");
     grpc_chttp2_mark_stream_closed(exec_ctx, t, s, true, true, GRPC_ERROR_NONE);
   }
   GRPC_CHTTP2_STREAM_UNREF(exec_ctx, s, "final_rst");
@@ -1697,9 +1697,9 @@ grpc_error *grpc_chttp2_header_parser_parse(grpc_exec_ctx *exec_ctx,
              and can avoid the extra write */
           GRPC_CHTTP2_STREAM_REF(s, "final_rst");
           grpc_closure_sched(
-              exec_ctx, grpc_closure_create(force_client_rst_stream, s,
-                                            grpc_combiner_finally_scheduler(
-                                                t->combiner, false)),
+              exec_ctx,
+              grpc_closure_create(force_client_rst_stream, s,
+                                  grpc_combiner_finally_scheduler(t->combiner)),
               GRPC_ERROR_NONE);
         }
         grpc_chttp2_mark_stream_closed(exec_ctx, t, s, true, false,

src/core/ext/transport/chttp2/transport/internal.h

@@ -58,7 +58,6 @@ typedef enum {
   GRPC_CHTTP2_WRITE_STATE_IDLE,
   GRPC_CHTTP2_WRITE_STATE_WRITING,
   GRPC_CHTTP2_WRITE_STATE_WRITING_WITH_MORE,
-  GRPC_CHTTP2_WRITE_STATE_WRITING_WITH_MORE_AND_COVERED_BY_POLLER,
 } grpc_chttp2_write_state;
 
 typedef enum {
@@ -443,7 +442,6 @@ struct grpc_chttp2_stream {
   grpc_slice fetching_slice;
   int64_t next_message_end_offset;
   int64_t flow_controlled_bytes_written;
-  bool complete_fetch_covered_by_poller;
   grpc_closure complete_fetch_locked;
   grpc_closure *fetching_send_message_finished;
 
@@ -534,8 +532,7 @@ struct grpc_chttp2_stream {
     The actual call chain is documented in the implementation of this function.
     */
 void grpc_chttp2_initiate_write(grpc_exec_ctx *exec_ctx,
-                                grpc_chttp2_transport *t,
-                                bool covered_by_poller, const char *reason);
+                                grpc_chttp2_transport *t, const char *reason);
 
 typedef enum {
   GRPC_CHTTP2_NOTHING_TO_WRITE,

src/core/ext/transport/chttp2/transport/parsing.c

@@ -418,7 +418,7 @@ static grpc_error *update_incoming_window(grpc_exec_ctx *exec_ctx,
   GRPC_CHTTP2_FLOW_DEBIT_TRANSPORT("parse", t, incoming_window,
                                    incoming_frame_size);
   if (t->incoming_window <= target_incoming_window / 2) {
-    grpc_chttp2_initiate_write(exec_ctx, t, false, "flow_control");
+    grpc_chttp2_initiate_write(exec_ctx, t, "flow_control");
   }
 
   return GRPC_ERROR_NONE;

src/core/ext/transport/chttp2/transport/writing.c

@@ -191,8 +191,7 @@ grpc_chttp2_begin_write_result grpc_chttp2_begin_write(
     while (grpc_chttp2_list_pop_stalled_by_transport(t, &s)) {
       if (!t->closed && grpc_chttp2_list_add_writable_stream(t, s) &&
           stream_ref_if_not_destroyed(&s->refcount->refs)) {
-        grpc_chttp2_initiate_write(exec_ctx, t, false,
-                                   "transport.read_flow_control");
+        grpc_chttp2_initiate_write(exec_ctx, t, "transport.read_flow_control");
       }
     }
   }

src/core/lib/iomgr/combiner.c

@@ -24,7 +24,7 @@
 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
 
-#include "src/core/lib/iomgr/workqueue.h"
+#include "src/core/lib/iomgr/executor.h"
 #include "src/core/lib/profiling/timers.h"
 
 grpc_tracer_flag grpc_combiner_trace = GRPC_TRACER_INITIALIZER(false);
@@ -41,93 +41,47 @@ grpc_tracer_flag grpc_combiner_trace = GRPC_TRACER_INITIALIZER(false);
 
 struct grpc_combiner {
   grpc_combiner *next_combiner_on_this_exec_ctx;
-  grpc_workqueue *optional_workqueue;
-  grpc_closure_scheduler uncovered_scheduler;
-  grpc_closure_scheduler covered_scheduler;
-  grpc_closure_scheduler uncovered_finally_scheduler;
-  grpc_closure_scheduler covered_finally_scheduler;
+  grpc_closure_scheduler scheduler;
+  grpc_closure_scheduler finally_scheduler;
   gpr_mpscq queue;
+  // either:
+  // a pointer to the initiating exec ctx if that is the only exec_ctx that has
+  // ever queued to this combiner, or NULL. If this is non-null, it's not
+  // dereferencable (since the initiating exec_ctx may have gone out of scope)
+  gpr_atm initiating_exec_ctx_or_null;
   // state is:
   // lower bit - zero if orphaned (STATE_UNORPHANED)
   // other bits - number of items queued on the lock (STATE_ELEM_COUNT_LOW_BIT)
   gpr_atm state;
-  // number of elements in the list that are covered by a poller: if >0, we can
-  // offload safely
-  gpr_atm elements_covered_by_poller;
   bool time_to_execute_final_list;
-  bool final_list_covered_by_poller;
   grpc_closure_list final_list;
   grpc_closure offload;
   gpr_refcount refs;
 };
 
-static void combiner_exec_uncovered(grpc_exec_ctx *exec_ctx,
-                                    grpc_closure *closure, grpc_error *error);
-static void combiner_exec_covered(grpc_exec_ctx *exec_ctx,
+static void combiner_exec(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
+                          grpc_error *error);
+static void combiner_finally_exec(grpc_exec_ctx *exec_ctx,
                                   grpc_closure *closure, grpc_error *error);
-static void combiner_finally_exec_uncovered(grpc_exec_ctx *exec_ctx,
-                                            grpc_closure *closure,
-                                            grpc_error *error);
-static void combiner_finally_exec_covered(grpc_exec_ctx *exec_ctx,
-                                          grpc_closure *closure,
-                                          grpc_error *error);
-
-static const grpc_closure_scheduler_vtable scheduler_uncovered = {
-    combiner_exec_uncovered, combiner_exec_uncovered,
-    "combiner:immediately:uncovered"};
-static const grpc_closure_scheduler_vtable scheduler_covered = {
-    combiner_exec_covered, combiner_exec_covered,
-    "combiner:immediately:covered"};
-static const grpc_closure_scheduler_vtable finally_scheduler_uncovered = {
-    combiner_finally_exec_uncovered, combiner_finally_exec_uncovered,
-    "combiner:finally:uncovered"};
-static const grpc_closure_scheduler_vtable finally_scheduler_covered = {
-    combiner_finally_exec_covered, combiner_finally_exec_covered,
-    "combiner:finally:covered"};
 
-static void offload(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error);
-
-typedef struct {
-  grpc_error *error;
-  bool covered_by_poller;
-} error_data;
-
-static uintptr_t pack_error_data(error_data d) {
-  return ((uintptr_t)d.error) | (d.covered_by_poller ? 1 : 0);
-}
-
-static error_data unpack_error_data(uintptr_t p) {
-  return (error_data){(grpc_error *)(p & ~(uintptr_t)1), p & 1};
-}
+static const grpc_closure_scheduler_vtable scheduler = {
+    combiner_exec, combiner_exec, "combiner:immediately"};
+static const grpc_closure_scheduler_vtable finally_scheduler = {
+    combiner_finally_exec, combiner_finally_exec, "combiner:finally"};
 
-static bool is_covered_by_poller(grpc_combiner *lock) {
-  return lock->final_list_covered_by_poller ||
-         gpr_atm_acq_load(&lock->elements_covered_by_poller) > 0;
-}
-
-#define IS_COVERED_BY_POLLER_FMT "(final=%d elems=%" PRIdPTR ")->%d"
-#define IS_COVERED_BY_POLLER_ARGS(lock)                      \
-  (lock)->final_list_covered_by_poller,                      \
-      gpr_atm_acq_load(&(lock)->elements_covered_by_poller), \
-      is_covered_by_poller((lock))
+static void offload(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error);
 
-grpc_combiner *grpc_combiner_create(grpc_workqueue *optional_workqueue) {
+grpc_combiner *grpc_combiner_create(void) {
   grpc_combiner *lock = gpr_malloc(sizeof(*lock));
   gpr_ref_init(&lock->refs, 1);
   lock->next_combiner_on_this_exec_ctx = NULL;
   lock->time_to_execute_final_list = false;
-  lock->optional_workqueue = optional_workqueue;
-  lock->final_list_covered_by_poller = false;
-  lock->uncovered_scheduler.vtable = &scheduler_uncovered;
-  lock->covered_scheduler.vtable = &scheduler_covered;
-  lock->uncovered_finally_scheduler.vtable = &finally_scheduler_uncovered;
-  lock->covered_finally_scheduler.vtable = &finally_scheduler_covered;
+  lock->scheduler.vtable = &scheduler;
+  lock->finally_scheduler.vtable = &finally_scheduler;
   gpr_atm_no_barrier_store(&lock->state, STATE_UNORPHANED);
-  gpr_atm_no_barrier_store(&lock->elements_covered_by_poller, 0);
   gpr_mpscq_init(&lock->queue);
   grpc_closure_list_init(&lock->final_list);
-  grpc_closure_init(&lock->offload, offload, lock,
-                    grpc_workqueue_scheduler(lock->optional_workqueue));
+  grpc_closure_init(&lock->offload, offload, lock, grpc_executor_scheduler);
   GRPC_COMBINER_TRACE(gpr_log(GPR_DEBUG, "C:%p create", lock));
   return lock;
 }
@@ -136,7 +90,6 @@ static void really_destroy(grpc_exec_ctx *exec_ctx, grpc_combiner *lock) {
   GRPC_COMBINER_TRACE(gpr_log(GPR_DEBUG, "C:%p really_destroy", lock));
   GPR_ASSERT(gpr_atm_no_barrier_load(&lock->state) == 0);
   gpr_mpscq_destroy(&lock->queue);
-  GRPC_WORKQUEUE_UNREF(exec_ctx, lock->optional_workqueue, "combiner");
   gpr_free(lock);
 }
 
@@ -193,48 +146,40 @@ static void push_first_on_exec_ctx(grpc_exec_ctx *exec_ctx,
   }
 }
 
-static void combiner_exec(grpc_exec_ctx *exec_ctx, grpc_combiner *lock,
-                          grpc_closure *cl, grpc_error *error,
-                          bool covered_by_poller) {
+#define COMBINER_FROM_CLOSURE_SCHEDULER(closure, scheduler_name) \
+  ((grpc_combiner *)(((char *)((closure)->scheduler)) -          \
+                     offsetof(grpc_combiner, scheduler_name)))
+
+static void combiner_exec(grpc_exec_ctx *exec_ctx, grpc_closure *cl,
+                          grpc_error *error) {
   GPR_TIMER_BEGIN("combiner.execute", 0);
+  grpc_combiner *lock = COMBINER_FROM_CLOSURE_SCHEDULER(cl, scheduler);
   gpr_atm last = gpr_atm_full_fetch_add(&lock->state, STATE_ELEM_COUNT_LOW_BIT);
-  GRPC_COMBINER_TRACE(gpr_log(
-      GPR_DEBUG, "C:%p grpc_combiner_execute c=%p cov=%d last=%" PRIdPTR, lock,
-      cl, covered_by_poller, last));
-  GPR_ASSERT(last & STATE_UNORPHANED);  // ensure lock has not been destroyed
-  assert(cl->cb);
-  cl->error_data.scratch =
-      pack_error_data((error_data){error, covered_by_poller});
-  if (covered_by_poller) {
-    gpr_atm_no_barrier_fetch_add(&lock->elements_covered_by_poller, 1);
-  }
-  gpr_mpscq_push(&lock->queue, &cl->next_data.atm_next);
+  GRPC_COMBINER_TRACE(gpr_log(GPR_DEBUG,
+                              "C:%p grpc_combiner_execute c=%p last=%" PRIdPTR,
+                              lock, cl, last));
   if (last == 1) {
+    gpr_atm_no_barrier_store(&lock->initiating_exec_ctx_or_null,
+                             (gpr_atm)exec_ctx);
     // first element on this list: add it to the list of combiner locks
     // executing within this exec_ctx
     push_last_on_exec_ctx(exec_ctx, lock);
+  } else {
+    // there may be a race with setting here: if that happens, we may delay
+    // offload for one or two actions, and that's fine
+    gpr_atm initiator =
+        gpr_atm_no_barrier_load(&lock->initiating_exec_ctx_or_null);
+    if (initiator != 0 && initiator != (gpr_atm)exec_ctx) {
+      gpr_atm_no_barrier_store(&lock->initiating_exec_ctx_or_null, 0);
+    }
   }
+  GPR_ASSERT(last & STATE_UNORPHANED);  // ensure lock has not been destroyed
+  assert(cl->cb);
+  cl->error_data.error = error;
+  gpr_mpscq_push(&lock->queue, &cl->next_data.atm_next);
   GPR_TIMER_END("combiner.execute", 0);
 }
 
-#define COMBINER_FROM_CLOSURE_SCHEDULER(closure, scheduler_name) \
-  ((grpc_combiner *)(((char *)((closure)->scheduler)) -          \
-                     offsetof(grpc_combiner, scheduler_name)))
-
-static void combiner_exec_uncovered(grpc_exec_ctx *exec_ctx, grpc_closure *cl,
-                                    grpc_error *error) {
-  combiner_exec(exec_ctx,
-                COMBINER_FROM_CLOSURE_SCHEDULER(cl, uncovered_scheduler), cl,
-                error, false);
-}
-
-static void combiner_exec_covered(grpc_exec_ctx *exec_ctx, grpc_closure *cl,
-                                  grpc_error *error) {
-  combiner_exec(exec_ctx,
-                COMBINER_FROM_CLOSURE_SCHEDULER(cl, covered_scheduler), cl,
-                error, true);
-}
-
 static void move_next(grpc_exec_ctx *exec_ctx) {
   exec_ctx->active_combiner =
       exec_ctx->active_combiner->next_combiner_on_this_exec_ctx;
@@ -250,8 +195,7 @@ static void offload(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {
 
 static void queue_offload(grpc_exec_ctx *exec_ctx, grpc_combiner *lock) {
   move_next(exec_ctx);
-  GRPC_COMBINER_TRACE(gpr_log(GPR_DEBUG, "C:%p queue_offload --> %p", lock,
-                              lock->optional_workqueue));
+  GRPC_COMBINER_TRACE(gpr_log(GPR_DEBUG, "C:%p queue_offload", lock));
   grpc_closure_sched(exec_ctx, &lock->offload, GRPC_ERROR_NONE);
 }
 
@@ -263,22 +207,23 @@ bool grpc_combiner_continue_exec_ctx(grpc_exec_ctx *exec_ctx) {
     return false;
   }
 
-  GRPC_COMBINER_TRACE(
-      gpr_log(GPR_DEBUG,
-              "C:%p grpc_combiner_continue_exec_ctx workqueue=%p "
-              "is_covered_by_poller=" IS_COVERED_BY_POLLER_FMT
-              " exec_ctx_ready_to_finish=%d "
-              "time_to_execute_final_list=%d",
-              lock, lock->optional_workqueue, IS_COVERED_BY_POLLER_ARGS(lock),
-              grpc_exec_ctx_ready_to_finish(exec_ctx),
-              lock->time_to_execute_final_list));
-
-  if (lock->optional_workqueue != NULL && is_covered_by_poller(lock) &&
-      grpc_exec_ctx_ready_to_finish(exec_ctx)) {
+  bool contended =
+      gpr_atm_no_barrier_load(&lock->initiating_exec_ctx_or_null) == 0;
+
+  GRPC_COMBINER_TRACE(gpr_log(GPR_DEBUG,
+                              "C:%p grpc_combiner_continue_exec_ctx "
+                              "contended=%d "
+                              "exec_ctx_ready_to_finish=%d "
+                              "time_to_execute_final_list=%d",
+                              lock, contended,
+                              grpc_exec_ctx_ready_to_finish(exec_ctx),
+                              lock->time_to_execute_final_list));
+
+  if (contended && grpc_exec_ctx_ready_to_finish(exec_ctx) &&
+      grpc_executor_is_threaded()) {
     GPR_TIMER_MARK("offload_from_finished_exec_ctx", 0);
-    // this execution context wants to move on, and we have a workqueue (and
-    // so can help the execution context out): schedule remaining work to be
-    // picked up on the workqueue
+    // this execution context wants to move on: schedule remaining work to be
+    // picked up on the executor
     queue_offload(exec_ctx, lock);
     GPR_TIMER_END("combiner.continue_exec_ctx", 0);
     return true;
@@ -295,29 +240,23 @@ bool grpc_combiner_continue_exec_ctx(grpc_exec_ctx *exec_ctx) {
       // queue is in an inconsistent state: use this as a cue that we should
       // go off and do something else for a while (and come back later)
       GPR_TIMER_MARK("delay_busy", 0);
-      if (lock->optional_workqueue != NULL && is_covered_by_poller(lock)) {
-        queue_offload(exec_ctx, lock);
-      }
+      queue_offload(exec_ctx, lock);
       GPR_TIMER_END("combiner.continue_exec_ctx", 0);
       return true;
     }
     GPR_TIMER_BEGIN("combiner.exec1", 0);
     grpc_closure *cl = (grpc_closure *)n;
-    error_data err = unpack_error_data(cl->error_data.scratch);
+    grpc_error *cl_err = cl->error_data.error;
 #ifndef NDEBUG
     cl->scheduled = false;
 #endif
-    cl->cb(exec_ctx, cl->cb_arg, err.error);
-    if (err.covered_by_poller) {
-      gpr_atm_no_barrier_fetch_add(&lock->elements_covered_by_poller, -1);
-    }
-    GRPC_ERROR_UNREF(err.error);
+    cl->cb(exec_ctx, cl->cb_arg, cl_err);
+    GRPC_ERROR_UNREF(cl_err);
     GPR_TIMER_END("combiner.exec1", 0);
   } else {
     grpc_closure *c = lock->final_list.head;
     GPR_ASSERT(c != NULL);
     grpc_closure_list_init(&lock->final_list);
-    lock->final_list_covered_by_poller = false;
     int loops = 0;
     while (c != NULL) {
       GPR_TIMER_BEGIN("combiner.exec_1final", 0);
@@ -383,20 +322,20 @@ bool grpc_combiner_continue_exec_ctx(grpc_exec_ctx *exec_ctx) {
 static void enqueue_finally(grpc_exec_ctx *exec_ctx, void *closure,
                             grpc_error *error);
 
-static void combiner_execute_finally(grpc_exec_ctx *exec_ctx,
-                                     grpc_combiner *lock, grpc_closure *closure,
-                                     grpc_error *error,
-                                     bool covered_by_poller) {
-  GRPC_COMBINER_TRACE(gpr_log(
-      GPR_DEBUG, "C:%p grpc_combiner_execute_finally c=%p; ac=%p; cov=%d", lock,
-      closure, exec_ctx->active_combiner, covered_by_poller));
+static void combiner_finally_exec(grpc_exec_ctx *exec_ctx,
+                                  grpc_closure *closure, grpc_error *error) {
+  grpc_combiner *lock =
+      COMBINER_FROM_CLOSURE_SCHEDULER(closure, finally_scheduler);
+  GRPC_COMBINER_TRACE(gpr_log(GPR_DEBUG,
+                              "C:%p grpc_combiner_execute_finally c=%p; ac=%p",
+                              lock, closure, exec_ctx->active_combiner));
   GPR_TIMER_BEGIN("combiner.execute_finally", 0);
   if (exec_ctx->active_combiner != lock) {
     GPR_TIMER_MARK("slowpath", 0);
-    grpc_closure_sched(
-        exec_ctx, grpc_closure_create(enqueue_finally, closure,
-                                      grpc_combiner_scheduler(lock, false)),
-        error);
+    grpc_closure_sched(exec_ctx,
+                       grpc_closure_create(enqueue_finally, closure,
+                                           grpc_combiner_scheduler(lock)),
+                       error);
     GPR_TIMER_END("combiner.execute_finally", 0);
     return;
   }
@@ -404,42 +343,20 @@ static void combiner_execute_finally(grpc_exec_ctx *exec_ctx,
   if (grpc_closure_list_empty(lock->final_list)) {
     gpr_atm_full_fetch_add(&lock->state, STATE_ELEM_COUNT_LOW_BIT);
   }
-  if (covered_by_poller) {
-    lock->final_list_covered_by_poller = true;
-  }
   grpc_closure_list_append(&lock->final_list, closure, error);
   GPR_TIMER_END("combiner.execute_finally", 0);
 }
 
 static void enqueue_finally(grpc_exec_ctx *exec_ctx, void *closure,
                             grpc_error *error) {
-  combiner_execute_finally(exec_ctx, exec_ctx->active_combiner, closure,
-                           GRPC_ERROR_REF(error), false);
-}
-
-static void combiner_finally_exec_uncovered(grpc_exec_ctx *exec_ctx,
-                                            grpc_closure *cl,
-                                            grpc_error *error) {
-  combiner_execute_finally(exec_ctx, COMBINER_FROM_CLOSURE_SCHEDULER(
-                                         cl, uncovered_finally_scheduler),
-                           cl, error, false);
-}
-
-static void combiner_finally_exec_covered(grpc_exec_ctx *exec_ctx,
-                                          grpc_closure *cl, grpc_error *error) {
-  combiner_execute_finally(
-      exec_ctx, COMBINER_FROM_CLOSURE_SCHEDULER(cl, covered_finally_scheduler),
-      cl, error, true);
+  combiner_finally_exec(exec_ctx, closure, GRPC_ERROR_REF(error));
 }
 
-grpc_closure_scheduler *grpc_combiner_scheduler(grpc_combiner *combiner,
-                                                bool covered_by_poller) {
-  return covered_by_poller ? &combiner->covered_scheduler
-                           : &combiner->uncovered_scheduler;
+grpc_closure_scheduler *grpc_combiner_scheduler(grpc_combiner *combiner) {
+  return &combiner->scheduler;
 }
 
 grpc_closure_scheduler *grpc_combiner_finally_scheduler(
-    grpc_combiner *combiner, bool covered_by_poller) {
-  return covered_by_poller ? &combiner->covered_finally_scheduler
-                           : &combiner->uncovered_finally_scheduler;
+    grpc_combiner *combiner) {
+  return &combiner->finally_scheduler;
 }

src/core/lib/iomgr/combiner.h

@@ -33,7 +33,7 @@
 
 // Initialize the lock, with an optional workqueue to shift load to when
 // necessary
-grpc_combiner *grpc_combiner_create(grpc_workqueue *optional_workqueue);
+grpc_combiner *grpc_combiner_create(void);
 
 //#define GRPC_COMBINER_REFCOUNT_DEBUG
 #ifdef GRPC_COMBINER_REFCOUNT_DEBUG
@@ -56,11 +56,9 @@ grpc_combiner *grpc_combiner_ref(grpc_combiner *lock GRPC_COMBINER_DEBUG_ARGS);
 void grpc_combiner_unref(grpc_exec_ctx *exec_ctx,
                          grpc_combiner *lock GRPC_COMBINER_DEBUG_ARGS);
 // Fetch a scheduler to schedule closures against
-grpc_closure_scheduler *grpc_combiner_scheduler(grpc_combiner *lock,
-                                                bool covered_by_poller);
+grpc_closure_scheduler *grpc_combiner_scheduler(grpc_combiner *lock);
 // Scheduler to execute \a action within the lock just prior to unlocking.
-grpc_closure_scheduler *grpc_combiner_finally_scheduler(grpc_combiner *lock,
-                                                        bool covered_by_poller);
+grpc_closure_scheduler *grpc_combiner_finally_scheduler(grpc_combiner *lock);
 
 bool grpc_combiner_continue_exec_ctx(grpc_exec_ctx *exec_ctx);
 

src/core/lib/iomgr/endpoint.c

@@ -54,10 +54,6 @@ char* grpc_endpoint_get_peer(grpc_endpoint* ep) {
 
 int grpc_endpoint_get_fd(grpc_endpoint* ep) { return ep->vtable->get_fd(ep); }
 
-grpc_workqueue* grpc_endpoint_get_workqueue(grpc_endpoint* ep) {
-  return ep->vtable->get_workqueue(ep);
-}
-
 grpc_resource_user* grpc_endpoint_get_resource_user(grpc_endpoint* ep) {
   return ep->vtable->get_resource_user(ep);
 }

src/core/lib/iomgr/endpoint.h

@@ -37,7 +37,6 @@ struct grpc_endpoint_vtable {
                grpc_slice_buffer *slices, grpc_closure *cb);
   void (*write)(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
                 grpc_slice_buffer *slices, grpc_closure *cb);
-  grpc_workqueue *(*get_workqueue)(grpc_endpoint *ep);
   void (*add_to_pollset)(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
                          grpc_pollset *pollset);
   void (*add_to_pollset_set)(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
@@ -63,9 +62,6 @@ char *grpc_endpoint_get_peer(grpc_endpoint *ep);
    */
 int grpc_endpoint_get_fd(grpc_endpoint *ep);
 
-/* Retrieve a reference to the workqueue associated with this endpoint */
-grpc_workqueue *grpc_endpoint_get_workqueue(grpc_endpoint *ep);
-
 /* Write slices out to the socket.
 
    If the connection is ready for more data after the end of the call, it

src/core/lib/iomgr/ev_epoll1_linux.c

@@ -43,7 +43,6 @@
 #include "src/core/lib/iomgr/iomgr_internal.h"
 #include "src/core/lib/iomgr/lockfree_event.h"
 #include "src/core/lib/iomgr/wakeup_fd_posix.h"
-#include "src/core/lib/iomgr/workqueue.h"
 #include "src/core/lib/profiling/timers.h"
 #include "src/core/lib/support/block_annotate.h"
 
@@ -115,7 +114,9 @@ struct grpc_pollset {
  * Pollset-set Declarations
  */
 
-struct grpc_pollset_set {};
+struct grpc_pollset_set {
+  char unused;
+};
 
 /*******************************************************************************
  * Common helpers
@@ -268,10 +269,6 @@ static void fd_notify_on_write(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
   grpc_lfev_notify_on(exec_ctx, &fd->write_closure, closure);
 }
 
-static grpc_workqueue *fd_get_workqueue(grpc_fd *fd) {
-  return (grpc_workqueue *)0xb0b51ed;
-}
-
 static void fd_become_readable(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
                                grpc_pollset *notifier) {
   grpc_lfev_set_ready(exec_ctx, &fd->read_closure);
@@ -298,8 +295,6 @@ GPR_TLS_DECL(g_current_thread_worker);
 static gpr_atm g_active_poller;
 static pollset_neighbourhood *g_neighbourhoods;
 static size_t g_num_neighbourhoods;
-static gpr_mu g_wq_mu;
-static grpc_closure_list g_wq_items;
 
 /* Return true if first in list */
 static bool worker_insert(grpc_pollset *pollset, grpc_pollset_worker *worker) {
@@ -348,8 +343,6 @@ static grpc_error *pollset_global_init(void) {
   gpr_atm_no_barrier_store(&g_active_poller, 0);
   global_wakeup_fd.read_fd = -1;
   grpc_error *err = grpc_wakeup_fd_init(&global_wakeup_fd);
-  gpr_mu_init(&g_wq_mu);
-  g_wq_items = (grpc_closure_list)GRPC_CLOSURE_LIST_INIT;
   if (err != GRPC_ERROR_NONE) return err;
   struct epoll_event ev = {.events = (uint32_t)(EPOLLIN | EPOLLET),
                            .data.ptr = &global_wakeup_fd};
@@ -368,7 +361,6 @@ static grpc_error *pollset_global_init(void) {
 static void pollset_global_shutdown(void) {
   gpr_tls_destroy(&g_current_thread_pollset);
   gpr_tls_destroy(&g_current_thread_worker);
-  gpr_mu_destroy(&g_wq_mu);
   if (global_wakeup_fd.read_fd != -1) grpc_wakeup_fd_destroy(&global_wakeup_fd);
   for (size_t i = 0; i < g_num_neighbourhoods; i++) {
     gpr_mu_destroy(&g_neighbourhoods[i].mu);
@@ -492,9 +484,6 @@ static grpc_error *pollset_epoll(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
   for (int i = 0; i < r; i++) {
     void *data_ptr = events[i].data.ptr;
     if (data_ptr == &global_wakeup_fd) {
-      gpr_mu_lock(&g_wq_mu);
-      grpc_closure_list_move(&g_wq_items, &exec_ctx->closure_list);
-      gpr_mu_unlock(&g_wq_mu);
       append_error(&error, grpc_wakeup_fd_consume_wakeup(&global_wakeup_fd),
                    err_desc);
     } else {
@@ -776,84 +765,6 @@ static grpc_error *pollset_kick(grpc_pollset *pollset,
 static void pollset_add_fd(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
                            grpc_fd *fd) {}
 
-/*******************************************************************************
- * Workqueue Definitions
- */
-
-#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
-static grpc_workqueue *workqueue_ref(grpc_workqueue *workqueue,
-                                     const char *file, int line,
-                                     const char *reason) {
-  return workqueue;
-}
-
-static void workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
-                            const char *file, int line, const char *reason) {}
-#else
-static grpc_workqueue *workqueue_ref(grpc_workqueue *workqueue) {
-  return workqueue;
-}
-
-static void workqueue_unref(grpc_exec_ctx *exec_ctx,
-                            grpc_workqueue *workqueue) {}
-#endif
-
-static void wq_sched(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
-                     grpc_error *error) {
-  // find a neighbourhood to wakeup
-  bool scheduled = false;
-  size_t initial_neighbourhood = choose_neighbourhood();
-  for (size_t i = 0; !scheduled && i < g_num_neighbourhoods; i++) {
-    pollset_neighbourhood *neighbourhood =
-        &g_neighbourhoods[(initial_neighbourhood + i) % g_num_neighbourhoods];
-    if (gpr_mu_trylock(&neighbourhood->mu)) {
-      if (neighbourhood->active_root != NULL) {
-        grpc_pollset *inspect = neighbourhood->active_root;
-        do {
-          if (gpr_mu_trylock(&inspect->mu)) {
-            if (inspect->root_worker != NULL) {
-              grpc_pollset_worker *inspect_worker = inspect->root_worker;
-              do {
-                if (inspect_worker->kick_state == UNKICKED) {
-                  inspect_worker->kick_state = KICKED;
-                  grpc_closure_list_append(
-                      &inspect_worker->schedule_on_end_work, closure, error);
-                  if (inspect_worker->initialized_cv) {
-                    gpr_cv_signal(&inspect_worker->cv);
-                  }
-                  scheduled = true;
-                }
-                inspect_worker = inspect_worker->next;
-              } while (!scheduled && inspect_worker != inspect->root_worker);
-            }
-            gpr_mu_unlock(&inspect->mu);
-          }
-          inspect = inspect->next;
-        } while (!scheduled && inspect != neighbourhood->active_root);
-      }
-      gpr_mu_unlock(&neighbourhood->mu);
-    }
-  }
-  if (!scheduled) {
-    gpr_mu_lock(&g_wq_mu);
-    grpc_closure_list_append(&g_wq_items, closure, error);
-    gpr_mu_unlock(&g_wq_mu);
-    GRPC_LOG_IF_ERROR("workqueue_scheduler",
-                      grpc_wakeup_fd_wakeup(&global_wakeup_fd));
-  }
-}
-
-static const grpc_closure_scheduler_vtable
-    singleton_workqueue_scheduler_vtable = {wq_sched, wq_sched,
-                                            "epoll1_workqueue"};
-
-static grpc_closure_scheduler singleton_workqueue_scheduler = {
-    &singleton_workqueue_scheduler_vtable};
-
-static grpc_closure_scheduler *workqueue_scheduler(grpc_workqueue *workqueue) {
-  return &singleton_workqueue_scheduler;
-}
-
 /*******************************************************************************
  * Pollset-set Definitions
  */
@@ -905,7 +816,6 @@ static const grpc_event_engine_vtable vtable = {
     .fd_notify_on_read = fd_notify_on_read,
     .fd_notify_on_write = fd_notify_on_write,
     .fd_get_read_notifier_pollset = fd_get_read_notifier_pollset,
-    .fd_get_workqueue = fd_get_workqueue,
 
     .pollset_init = pollset_init,
     .pollset_shutdown = pollset_shutdown,
@@ -923,10 +833,6 @@ static const grpc_event_engine_vtable vtable = {
     .pollset_set_add_fd = pollset_set_add_fd,
     .pollset_set_del_fd = pollset_set_del_fd,
 
-    .workqueue_ref = workqueue_ref,
-    .workqueue_unref = workqueue_unref,
-    .workqueue_scheduler = workqueue_scheduler,
-
     .shutdown_engine = shutdown_engine,
 };
 

src/core/lib/iomgr/ev_epoll_limited_pollers_linux.c

@@ -46,7 +46,6 @@
 #include "src/core/lib/iomgr/lockfree_event.h"
 #include "src/core/lib/iomgr/timer.h"
 #include "src/core/lib/iomgr/wakeup_fd_posix.h"
-#include "src/core/lib/iomgr/workqueue.h"
 #include "src/core/lib/profiling/timers.h"
 #include "src/core/lib/support/block_annotate.h"
 #include "src/core/lib/support/env.h"
@@ -169,13 +168,15 @@ static void fd_global_shutdown(void);
  * Polling island Declarations
  */
 
-#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
+//#define PI_REFCOUNT_DEBUG
+
+#ifdef PI_REFCOUNT_DEBUG
 
 #define PI_ADD_REF(p, r) pi_add_ref_dbg((p), (r), __FILE__, __LINE__)
 #define PI_UNREF(exec_ctx, p, r) \
   pi_unref_dbg((exec_ctx), (p), (r), __FILE__, __LINE__)
 
-#else /* defined(GRPC_WORKQUEUE_REFCOUNT_DEBUG) */
+#else /* defined(PI_REFCOUNT_DEBUG) */
 
 #define PI_ADD_REF(p, r) pi_add_ref((p))
 #define PI_UNREF(exec_ctx, p, r) pi_unref((exec_ctx), (p))
@@ -189,8 +190,6 @@ typedef struct worker_node {
 
 /* This is also used as grpc_workqueue (by directly casing it) */
 typedef struct polling_island {
-  grpc_closure_scheduler workqueue_scheduler;
-
   gpr_mu mu;
   /* Ref count. Use PI_ADD_REF() and PI_UNREF() macros to increment/decrement
      the refcount.
@@ -211,15 +210,6 @@ typedef struct polling_island {
 
   /* Number of threads currently polling on this island */
   gpr_atm poller_count;
-  /* Mutex guarding the read end of the workqueue (must be held to pop from
-   * workqueue_items) */
-  gpr_mu workqueue_read_mu;
-  /* Queue of closures to be executed */
-  gpr_mpscq workqueue_items;
-  /* Count of items in workqueue_items */
-  gpr_atm workqueue_item_count;
-  /* Wakeup fd used to wake pollers to check the contents of workqueue_items */
-  grpc_wakeup_fd workqueue_wakeup_fd;
 
   /* The list of workers waiting to do polling on this polling island */
   gpr_mu worker_list_mu;
@@ -308,8 +298,6 @@ static __thread polling_island *g_current_thread_polling_island;
 
 /* Forward declaration */
 static void polling_island_delete(grpc_exec_ctx *exec_ctx, polling_island *pi);
-static void workqueue_enqueue(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
-                              grpc_error *error);
 
 #ifdef GRPC_TSAN
 /* Currently TSAN may incorrectly flag data races between epoll_ctl and
@@ -322,13 +310,10 @@ static void workqueue_enqueue(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
 gpr_atm g_epoll_sync;
 #endif /* defined(GRPC_TSAN) */
 
-static const grpc_closure_scheduler_vtable workqueue_scheduler_vtable = {
-    workqueue_enqueue, workqueue_enqueue, "workqueue"};
-
 static void pi_add_ref(polling_island *pi);
 static void pi_unref(grpc_exec_ctx *exec_ctx, polling_island *pi);
 
-#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
+#ifdef PI_REFCOUNT_DEBUG
 static void pi_add_ref_dbg(polling_island *pi, const char *reason,
                            const char *file, int line) {
   long old_cnt = gpr_atm_acq_load(&pi->ref_count);
@@ -344,36 +329,6 @@ static void pi_unref_dbg(grpc_exec_ctx *exec_ctx, polling_island *pi,
   gpr_log(GPR_DEBUG, "Unref pi: %p, old:%ld -> new:%ld (%s) - (%s, %d)",
           (void *)pi, old_cnt, (old_cnt - 1), reason, file, line);
 }
-
-static grpc_workqueue *workqueue_ref(grpc_workqueue *workqueue,
-                                     const char *file, int line,
-                                     const char *reason) {
-  if (workqueue != NULL) {
-    pi_add_ref_dbg((polling_island *)workqueue, reason, file, line);
-  }
-  return workqueue;
-}
-
-static void workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
-                            const char *file, int line, const char *reason) {
-  if (workqueue != NULL) {
-    pi_unref_dbg(exec_ctx, (polling_island *)workqueue, reason, file, line);
-  }
-}
-#else
-static grpc_workqueue *workqueue_ref(grpc_workqueue *workqueue) {
-  if (workqueue != NULL) {
-    pi_add_ref((polling_island *)workqueue);
-  }
-  return workqueue;
-}
-
-static void workqueue_unref(grpc_exec_ctx *exec_ctx,
-                            grpc_workqueue *workqueue) {
-  if (workqueue != NULL) {
-    pi_unref(exec_ctx, (polling_island *)workqueue);
-  }
-}
 #endif
 
 static void pi_add_ref(polling_island *pi) {
@@ -577,17 +532,12 @@ static polling_island *polling_island_create(grpc_exec_ctx *exec_ctx,
   *error = GRPC_ERROR_NONE;
 
   pi = gpr_malloc(sizeof(*pi));
-  pi->workqueue_scheduler.vtable = &workqueue_scheduler_vtable;
   gpr_mu_init(&pi->mu);
   pi->fd_cnt = 0;
   pi->fd_capacity = 0;
   pi->fds = NULL;
   pi->epoll_fd = -1;
 
-  gpr_mu_init(&pi->workqueue_read_mu);
-  gpr_mpscq_init(&pi->workqueue_items);
-  gpr_atm_rel_store(&pi->workqueue_item_count, 0);
-
   gpr_atm_rel_store(&pi->ref_count, 0);
   gpr_atm_rel_store(&pi->poller_count, 0);
   gpr_atm_rel_store(&pi->merged_to, (gpr_atm)NULL);
@@ -595,11 +545,6 @@ static polling_island *polling_island_create(grpc_exec_ctx *exec_ctx,
   gpr_mu_init(&pi->worker_list_mu);
   worker_node_init(&pi->worker_list_head);
 
-  if (!append_error(error, grpc_wakeup_fd_init(&pi->workqueue_wakeup_fd),
-                    err_desc)) {
-    goto done;
-  }
-
   pi->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
 
   if (pi->epoll_fd < 0) {
@@ -607,8 +552,6 @@ static polling_island *polling_island_create(grpc_exec_ctx *exec_ctx,
     goto done;
   }
 
-  polling_island_add_wakeup_fd_locked(pi, &pi->workqueue_wakeup_fd, error);
-
   if (initial_fd != NULL) {
     polling_island_add_fds_locked(pi, &initial_fd, 1, true, error);
   }
@@ -627,11 +570,7 @@ static void polling_island_delete(grpc_exec_ctx *exec_ctx, polling_island *pi) {
   if (pi->epoll_fd >= 0) {
     close(pi->epoll_fd);
   }
-  GPR_ASSERT(gpr_atm_no_barrier_load(&pi->workqueue_item_count) == 0);
-  gpr_mu_destroy(&pi->workqueue_read_mu);
-  gpr_mpscq_destroy(&pi->workqueue_items);
   gpr_mu_destroy(&pi->mu);
-  grpc_wakeup_fd_destroy(&pi->workqueue_wakeup_fd);
   gpr_mu_destroy(&pi->worker_list_mu);
   GPR_ASSERT(is_worker_node_detached(&pi->worker_list_head));
 
@@ -779,45 +718,6 @@ static void polling_island_unlock_pair(polling_island *p, polling_island *q) {
   }
 }
 
-static void workqueue_maybe_wakeup(polling_island *pi) {
-  /* If this thread is the current poller, then it may be that it's about to
-     decrement the current poller count, so we need to look past this thread */
-  bool is_current_poller = (g_current_thread_polling_island == pi);
-  gpr_atm min_current_pollers_for_wakeup = is_current_poller ? 1 : 0;
-  gpr_atm current_pollers = gpr_atm_no_barrier_load(&pi->poller_count);
-  /* Only issue a wakeup if it's likely that some poller could come in and take
-     it right now. Note that since we do an anticipatory mpscq_pop every poll
-     loop, it's ok if we miss the wakeup here, as we'll get the work item when
-     the next poller enters anyway. */
-  if (current_pollers > min_current_pollers_for_wakeup) {
-    GRPC_LOG_IF_ERROR("workqueue_wakeup_fd",
-                      grpc_wakeup_fd_wakeup(&pi->workqueue_wakeup_fd));
-  }
-}
-
-static void workqueue_move_items_to_parent(polling_island *q) {
-  polling_island *p = (polling_island *)gpr_atm_no_barrier_load(&q->merged_to);
-  if (p == NULL) {
-    return;
-  }
-  gpr_mu_lock(&q->workqueue_read_mu);
-  int num_added = 0;
-  while (gpr_atm_no_barrier_load(&q->workqueue_item_count) > 0) {
-    gpr_mpscq_node *n = gpr_mpscq_pop(&q->workqueue_items);
-    if (n != NULL) {
-      gpr_atm_no_barrier_fetch_add(&q->workqueue_item_count, -1);
-      gpr_atm_no_barrier_fetch_add(&p->workqueue_item_count, 1);
-      gpr_mpscq_push(&p->workqueue_items, n);
-      num_added++;
-    }
-  }
-  gpr_mu_unlock(&q->workqueue_read_mu);
-  if (num_added > 0) {
-    workqueue_maybe_wakeup(p);
-  }
-  workqueue_move_items_to_parent(p);
-}
-
 static polling_island *polling_island_merge(polling_island *p,
                                             polling_island *q,
                                             grpc_error **error) {
@@ -842,8 +742,6 @@ static polling_island *polling_island_merge(polling_island *p,
     /* Add the 'merged_to' link from p --> q */
     gpr_atm_rel_store(&p->merged_to, (gpr_atm)q);
     PI_ADD_REF(q, "pi_merge"); /* To account for the new incoming ref from p */
-
-    workqueue_move_items_to_parent(p);
   }
   /* else if p == q, nothing needs to be done */
 
@@ -854,32 +752,6 @@ static polling_island *polling_island_merge(polling_island *p,
   return q;
 }
 
-static void workqueue_enqueue(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
-                              grpc_error *error) {
-  GPR_TIMER_BEGIN("workqueue.enqueue", 0);
-  grpc_workqueue *workqueue = (grpc_workqueue *)closure->scheduler;
-  /* take a ref to the workqueue: otherwise it can happen that whatever events
-   * this kicks off ends up destroying the workqueue before this function
-   * completes */
-  GRPC_WORKQUEUE_REF(workqueue, "enqueue");
-  polling_island *pi = (polling_island *)workqueue;
-  gpr_atm last = gpr_atm_no_barrier_fetch_add(&pi->workqueue_item_count, 1);
-  closure->error_data.error = error;
-  gpr_mpscq_push(&pi->workqueue_items, &closure->next_data.atm_next);
-  if (last == 0) {
-    workqueue_maybe_wakeup(pi);
-  }
-  workqueue_move_items_to_parent(pi);
-  GRPC_WORKQUEUE_UNREF(exec_ctx, workqueue, "enqueue");
-  GPR_TIMER_END("workqueue.enqueue", 0);
-}
-
-static grpc_closure_scheduler *workqueue_scheduler(grpc_workqueue *workqueue) {
-  polling_island *pi = (polling_island *)workqueue;
-  return workqueue == NULL ? grpc_schedule_on_exec_ctx
-                           : &pi->workqueue_scheduler;
-}
-
 static grpc_error *polling_island_global_init() {
   grpc_error *error = GRPC_ERROR_NONE;
 
@@ -1138,14 +1010,6 @@ static void fd_notify_on_write(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
   grpc_lfev_notify_on(exec_ctx, &fd->write_closure, closure);
 }
 
-static grpc_workqueue *fd_get_workqueue(grpc_fd *fd) {
-  gpr_mu_lock(&fd->po.mu);
-  grpc_workqueue *workqueue =
-      GRPC_WORKQUEUE_REF((grpc_workqueue *)fd->po.pi, "fd_get_workqueue");
-  gpr_mu_unlock(&fd->po.mu);
-  return workqueue;
-}
-
 /*******************************************************************************
  * Pollset Definitions
  */
@@ -1417,33 +1281,6 @@ static void pollset_destroy(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset) {
   gpr_mu_destroy(&pollset->po.mu);
 }
 
-static bool maybe_do_workqueue_work(grpc_exec_ctx *exec_ctx,
-                                    polling_island *pi) {
-  if (gpr_mu_trylock(&pi->workqueue_read_mu)) {
-    gpr_mpscq_node *n = gpr_mpscq_pop(&pi->workqueue_items);
-    gpr_mu_unlock(&pi->workqueue_read_mu);
-    if (n != NULL) {
-      if (gpr_atm_full_fetch_add(&pi->workqueue_item_count, -1) > 1) {
-        workqueue_maybe_wakeup(pi);
-      }
-      grpc_closure *c = (grpc_closure *)n;
-      grpc_error *error = c->error_data.error;
-#ifndef NDEBUG
-      c->scheduled = false;
-#endif
-      c->cb(exec_ctx, c->cb_arg, error);
-      GRPC_ERROR_UNREF(error);
-      return true;
-    } else if (gpr_atm_no_barrier_load(&pi->workqueue_item_count) > 0) {
-      /* n == NULL might mean there's work but it's not available to be popped
-       * yet - try to ensure another workqueue wakes up to check shortly if so
-       */
-      workqueue_maybe_wakeup(pi);
-    }
-  }
-  return false;
-}
-
 /* NOTE: This function may modify 'now' */
 static bool acquire_polling_lease(grpc_pollset_worker *worker,
                                   polling_island *pi, gpr_timespec deadline,
@@ -1579,12 +1416,7 @@ static void pollset_do_epoll_pwait(grpc_exec_ctx *exec_ctx, int epoll_fd,
 
   for (int i = 0; i < ep_rv; ++i) {
     void *data_ptr = ep_ev[i].data.ptr;
-    if (data_ptr == &pi->workqueue_wakeup_fd) {
-      append_error(error,
-                   grpc_wakeup_fd_consume_wakeup(&pi->workqueue_wakeup_fd),
-                   err_desc);
-      maybe_do_workqueue_work(exec_ctx, pi);
-    } else if (data_ptr == &polling_island_wakeup_fd) {
+    if (data_ptr == &polling_island_wakeup_fd) {
       GRPC_POLLING_TRACE(
           "pollset_work: pollset: %p, worker: %p polling island (epoll_fd: "
           "%d) got merged",
@@ -1660,15 +1492,10 @@ static void pollset_work_and_unlock(grpc_exec_ctx *exec_ctx,
   PI_ADD_REF(pi, "ps_work");
   gpr_mu_unlock(&pollset->po.mu);
 
-  /* If we get some workqueue work to do, it might end up completing an item on
-     the completion queue, so there's no need to poll... so we skip that and
-     redo the complete loop to verify */
-  if (!maybe_do_workqueue_work(exec_ctx, pi)) {
-    g_current_thread_polling_island = pi;
-    pollset_do_epoll_pwait(exec_ctx, epoll_fd, pollset, pi, worker, now,
-                           deadline, sig_mask, error);
-    g_current_thread_polling_island = NULL;
-  }
+  g_current_thread_polling_island = pi;
+  pollset_do_epoll_pwait(exec_ctx, epoll_fd, pollset, pi, worker, now, deadline,
+                         sig_mask, error);
+  g_current_thread_polling_island = NULL;
 
   GPR_ASSERT(pi != NULL);
 
@@ -2021,7 +1848,6 @@ static const grpc_event_engine_vtable vtable = {
     .fd_notify_on_read = fd_notify_on_read,
     .fd_notify_on_write = fd_notify_on_write,
     .fd_get_read_notifier_pollset = fd_get_read_notifier_pollset,
-    .fd_get_workqueue = fd_get_workqueue,
 
     .pollset_init = pollset_init,
     .pollset_shutdown = pollset_shutdown,
@@ -2039,10 +1865,6 @@ static const grpc_event_engine_vtable vtable = {
     .pollset_set_add_fd = pollset_set_add_fd,
     .pollset_set_del_fd = pollset_set_del_fd,
 
-    .workqueue_ref = workqueue_ref,
-    .workqueue_unref = workqueue_unref,
-    .workqueue_scheduler = workqueue_scheduler,
-
     .shutdown_engine = shutdown_engine,
 };
 

src/core/lib/iomgr/ev_epoll_thread_pool_linux.c

@@ -46,7 +46,6 @@
 #include "src/core/lib/iomgr/lockfree_event.h"
 #include "src/core/lib/iomgr/timer.h"
 #include "src/core/lib/iomgr/wakeup_fd_posix.h"
-#include "src/core/lib/iomgr/workqueue.h"
 #include "src/core/lib/profiling/timers.h"
 #include "src/core/lib/support/block_annotate.h"
 
@@ -94,23 +93,22 @@ static void fd_global_shutdown(void);
  * epoll set Declarations
  */
 
-#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
+//#define EPS_REFCOUNT_DEBUG
+
+#ifdef EPS_REFCOUNT_DEBUG
 
 #define EPS_ADD_REF(p, r) eps_add_ref_dbg((p), (r), __FILE__, __LINE__)
 #define EPS_UNREF(exec_ctx, p, r) \
   eps_unref_dbg((exec_ctx), (p), (r), __FILE__, __LINE__)
 
-#else /* defined(GRPC_WORKQUEUE_REFCOUNT_DEBUG) */
+#else /* defined(EPS_REFCOUNT_DEBUG) */
 
 #define EPS_ADD_REF(p, r) eps_add_ref((p))
 #define EPS_UNREF(exec_ctx, p, r) eps_unref((exec_ctx), (p))
 
 #endif /* !defined(GRPC_EPS_REF_COUNT_DEBUG) */
 
-/* This is also used as grpc_workqueue (by directly casting it) */
 typedef struct epoll_set {
-  grpc_closure_scheduler workqueue_scheduler;
-
   /* Mutex poller should acquire to poll this. This enforces that only one
    * poller can be polling on epoll_set at any time */
   gpr_mu mu;
@@ -124,15 +122,6 @@ typedef struct epoll_set {
 
   /* Number of threads currently polling on this epoll set*/
   gpr_atm poller_count;
-  /* Mutex guarding the read end of the workqueue (must be held to pop from
-   * workqueue_items) */
-  gpr_mu workqueue_read_mu;
-  /* Queue of closures to be executed */
-  gpr_mpscq workqueue_items;
-  /* Count of items in workqueue_items */
-  gpr_atm workqueue_item_count;
-  /* Wakeup fd used to wake pollers to check the contents of workqueue_items */
-  grpc_wakeup_fd workqueue_wakeup_fd;
 
   /* Is the epoll set shutdown */
   gpr_atm is_shutdown;
@@ -166,7 +155,9 @@ struct grpc_pollset {
 /*******************************************************************************
  * Pollset-set Declarations
  */
-struct grpc_pollset_set {};
+struct grpc_pollset_set {
+  char unused;
+};
 
 /*****************************************************************************
  * Dedicated polling threads and pollsets - Declarations
@@ -220,8 +211,6 @@ static __thread epoll_set *g_current_thread_epoll_set;
 
 /* Forward declaration */
 static void epoll_set_delete(epoll_set *eps);
-static void workqueue_enqueue(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
-                              grpc_error *error);
 
 #ifdef GRPC_TSAN
 /* Currently TSAN may incorrectly flag data races between epoll_ctl and
@@ -234,13 +223,10 @@ static void workqueue_enqueue(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
 gpr_atm g_epoll_sync;
 #endif /* defined(GRPC_TSAN) */
 
-static const grpc_closure_scheduler_vtable workqueue_scheduler_vtable = {
-    workqueue_enqueue, workqueue_enqueue, "workqueue"};
-
 static void eps_add_ref(epoll_set *eps);
 static void eps_unref(grpc_exec_ctx *exec_ctx, epoll_set *eps);
 
-#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
+#ifdef EPS_REFCOUNT_DEBUG
 static void eps_add_ref_dbg(epoll_set *eps, const char *reason,
                             const char *file, int line) {
   long old_cnt = gpr_atm_acq_load(&eps->ref_count);
@@ -256,36 +242,6 @@ static void eps_unref_dbg(grpc_exec_ctx *exec_ctx, epoll_set *eps,
   gpr_log(GPR_DEBUG, "Unref eps: %p, old:%ld -> new:%ld (%s) - (%s, %d)",
           (void *)eps, old_cnt, (old_cnt - 1), reason, file, line);
 }
-
-static grpc_workqueue *workqueue_ref(grpc_workqueue *workqueue,
-                                     const char *file, int line,
-                                     const char *reason) {
-  if (workqueue != NULL) {
-    eps_add_ref_dbg((epoll_set *)workqueue, reason, file, line);
-  }
-  return workqueue;
-}
-
-static void workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
-                            const char *file, int line, const char *reason) {
-  if (workqueue != NULL) {
-    eps_unref_dbg(exec_ctx, (epoll_set *)workqueue, reason, file, line);
-  }
-}
-#else
-static grpc_workqueue *workqueue_ref(grpc_workqueue *workqueue) {
-  if (workqueue != NULL) {
-    eps_add_ref((epoll_set *)workqueue);
-  }
-  return workqueue;
-}
-
-static void workqueue_unref(grpc_exec_ctx *exec_ctx,
-                            grpc_workqueue *workqueue) {
-  if (workqueue != NULL) {
-    eps_unref(exec_ctx, (epoll_set *)workqueue);
-  }
-}
 #endif
 
 static void eps_add_ref(epoll_set *eps) {
@@ -379,24 +335,15 @@ static epoll_set *epoll_set_create(grpc_error **error) {
   *error = GRPC_ERROR_NONE;
 
   eps = gpr_malloc(sizeof(*eps));
-  eps->workqueue_scheduler.vtable = &workqueue_scheduler_vtable;
   eps->epoll_fd = -1;
 
   gpr_mu_init(&eps->mu);
-  gpr_mu_init(&eps->workqueue_read_mu);
-  gpr_mpscq_init(&eps->workqueue_items);
-  gpr_atm_rel_store(&eps->workqueue_item_count, 0);
 
   gpr_atm_rel_store(&eps->ref_count, 0);
   gpr_atm_rel_store(&eps->poller_count, 0);
 
   gpr_atm_rel_store(&eps->is_shutdown, false);
 
-  if (!append_error(error, grpc_wakeup_fd_init(&eps->workqueue_wakeup_fd),
-                    err_desc)) {
-    goto done;
-  }
-
   eps->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
 
   if (eps->epoll_fd < 0) {
@@ -404,8 +351,6 @@ static epoll_set *epoll_set_create(grpc_error **error) {
     goto done;
   }
 
-  epoll_set_add_wakeup_fd_locked(eps, &eps->workqueue_wakeup_fd, error);
-
 done:
   if (*error != GRPC_ERROR_NONE) {
     epoll_set_delete(eps);
@@ -419,57 +364,11 @@ static void epoll_set_delete(epoll_set *eps) {
     close(eps->epoll_fd);
   }
 
-  GPR_ASSERT(gpr_atm_no_barrier_load(&eps->workqueue_item_count) == 0);
   gpr_mu_destroy(&eps->mu);
-  gpr_mu_destroy(&eps->workqueue_read_mu);
-  gpr_mpscq_destroy(&eps->workqueue_items);
-  grpc_wakeup_fd_destroy(&eps->workqueue_wakeup_fd);
 
   gpr_free(eps);
 }
 
-static void workqueue_maybe_wakeup(epoll_set *eps) {
-  /* If this thread is the current poller, then it may be that it's about to
-     decrement the current poller count, so we need to look past this thread */
-  bool is_current_poller = (g_current_thread_epoll_set == eps);
-  gpr_atm min_current_pollers_for_wakeup = is_current_poller ? 1 : 0;
-  gpr_atm current_pollers = gpr_atm_no_barrier_load(&eps->poller_count);
-  /* Only issue a wakeup if it's likely that some poller could come in and take
-     it right now. Note that since we do an anticipatory mpscq_pop every poll
-     loop, it's ok if we miss the wakeup here, as we'll get the work item when
-     the next poller enters anyway. */
-  if (current_pollers > min_current_pollers_for_wakeup) {
-    GRPC_LOG_IF_ERROR("workqueue_wakeup_fd",
-                      grpc_wakeup_fd_wakeup(&eps->workqueue_wakeup_fd));
-  }
-}
-
-static void workqueue_enqueue(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
-                              grpc_error *error) {
-  GPR_TIMER_BEGIN("workqueue.enqueue", 0);
-  grpc_workqueue *workqueue = (grpc_workqueue *)closure->scheduler;
-  /* take a ref to the workqueue: otherwise it can happen that whatever events
-   * this kicks off ends up destroying the workqueue before this function
-   * completes */
-  GRPC_WORKQUEUE_REF(workqueue, "enqueue");
-  epoll_set *eps = (epoll_set *)workqueue;
-  gpr_atm last = gpr_atm_no_barrier_fetch_add(&eps->workqueue_item_count, 1);
-  closure->error_data.error = error;
-  gpr_mpscq_push(&eps->workqueue_items, &closure->next_data.atm_next);
-  if (last == 0) {
-    workqueue_maybe_wakeup(eps);
-  }
-
-  GRPC_WORKQUEUE_UNREF(exec_ctx, workqueue, "enqueue");
-  GPR_TIMER_END("workqueue.enqueue", 0);
-}
-
-static grpc_closure_scheduler *workqueue_scheduler(grpc_workqueue *workqueue) {
-  epoll_set *eps = (epoll_set *)workqueue;
-  return workqueue == NULL ? grpc_schedule_on_exec_ctx
-                           : &eps->workqueue_scheduler;
-}
-
 static grpc_error *epoll_set_global_init() {
   grpc_error *error = GRPC_ERROR_NONE;
 
@@ -665,8 +564,6 @@ static void fd_notify_on_write(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
   grpc_lfev_notify_on(exec_ctx, &fd->write_closure, closure);
 }
 
-static grpc_workqueue *fd_get_workqueue(grpc_fd *fd) { return NULL; }
-
 /*******************************************************************************
  * Pollset Definitions
  */
@@ -850,32 +747,6 @@ static void pollset_destroy(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset) {
   gpr_mu_destroy(&pollset->mu);
 }
 
-static bool maybe_do_workqueue_work(grpc_exec_ctx *exec_ctx, epoll_set *eps) {
-  if (gpr_mu_trylock(&eps->workqueue_read_mu)) {
-    gpr_mpscq_node *n = gpr_mpscq_pop(&eps->workqueue_items);
-    gpr_mu_unlock(&eps->workqueue_read_mu);
-    if (n != NULL) {
-      if (gpr_atm_full_fetch_add(&eps->workqueue_item_count, -1) > 1) {
-        workqueue_maybe_wakeup(eps);
-      }
-      grpc_closure *c = (grpc_closure *)n;
-      grpc_error *error = c->error_data.error;
-#ifndef NDEBUG
-      c->scheduled = false;
-#endif
-      c->cb(exec_ctx, c->cb_arg, error);
-      GRPC_ERROR_UNREF(error);
-      return true;
-    } else if (gpr_atm_no_barrier_load(&eps->workqueue_item_count) > 0) {
-      /* n == NULL might mean there's work but it's not available to be popped
-       * yet - try to ensure another workqueue wakes up to check shortly if so
-       */
-      workqueue_maybe_wakeup(eps);
-    }
-  }
-  return false;
-}
-
 /* Blocking call */
 static void acquire_epoll_lease(epoll_set *eps) {
   if (g_num_threads_per_eps > 1) {
@@ -919,12 +790,7 @@ static void do_epoll_wait(grpc_exec_ctx *exec_ctx, int epoll_fd, epoll_set *eps,
 
   for (int i = 0; i < ep_rv; ++i) {
     void *data_ptr = ep_ev[i].data.ptr;
-    if (data_ptr == &eps->workqueue_wakeup_fd) {
-      append_error(error,
-                   grpc_wakeup_fd_consume_wakeup(&eps->workqueue_wakeup_fd),
-                   err_desc);
-      maybe_do_workqueue_work(exec_ctx, eps);
-    } else if (data_ptr == &epoll_set_wakeup_fd) {
+    if (data_ptr == &epoll_set_wakeup_fd) {
       gpr_atm_rel_store(&eps->is_shutdown, 1);
       gpr_log(GPR_INFO, "pollset poller: shutdown set");
     } else {
@@ -951,18 +817,13 @@ static void epoll_set_work(grpc_exec_ctx *exec_ctx, epoll_set *eps,
      epoll set. */
   epoll_fd = eps->epoll_fd;
 
-  /* If we get some workqueue work to do, it might end up completing an item on
-     the completion queue, so there's no need to poll... so we skip that and
-     redo the complete loop to verify */
-  if (!maybe_do_workqueue_work(exec_ctx, eps)) {
-    gpr_atm_no_barrier_fetch_add(&eps->poller_count, 1);
-    g_current_thread_epoll_set = eps;
+  gpr_atm_no_barrier_fetch_add(&eps->poller_count, 1);
+  g_current_thread_epoll_set = eps;
 
-    do_epoll_wait(exec_ctx, epoll_fd, eps, error);
+  do_epoll_wait(exec_ctx, epoll_fd, eps, error);
 
-    g_current_thread_epoll_set = NULL;
-    gpr_atm_no_barrier_fetch_add(&eps->poller_count, -1);
-  }
+  g_current_thread_epoll_set = NULL;
+  gpr_atm_no_barrier_fetch_add(&eps->poller_count, -1);
 
   GPR_TIMER_END("epoll_set_work", 0);
 }
@@ -1105,7 +966,6 @@ static const grpc_event_engine_vtable vtable = {
     .fd_notify_on_read = fd_notify_on_read,
     .fd_notify_on_write = fd_notify_on_write,
     .fd_get_read_notifier_pollset = fd_get_read_notifier_pollset,
-    .fd_get_workqueue = fd_get_workqueue,
 
     .pollset_init = pollset_init,
     .pollset_shutdown = pollset_shutdown,
@@ -1123,10 +983,6 @@ static const grpc_event_engine_vtable vtable = {
     .pollset_set_add_fd = pollset_set_add_fd,
     .pollset_set_del_fd = pollset_set_del_fd,
 
-    .workqueue_ref = workqueue_ref,
-    .workqueue_unref = workqueue_unref,
-    .workqueue_scheduler = workqueue_scheduler,
-
     .shutdown_engine = shutdown_engine,
 };
 

src/core/lib/iomgr/ev_epollex_linux.c

@@ -44,7 +44,6 @@
 #include "src/core/lib/iomgr/sys_epoll_wrapper.h"
 #include "src/core/lib/iomgr/timer.h"
 #include "src/core/lib/iomgr/wakeup_fd_posix.h"
-#include "src/core/lib/iomgr/workqueue.h"
 #include "src/core/lib/profiling/timers.h"
 #include "src/core/lib/support/block_annotate.h"
 #include "src/core/lib/support/spinlock.h"
@@ -124,17 +123,6 @@ struct grpc_fd {
      Ref/Unref by two to avoid altering the orphaned bit */
   gpr_atm refst;
 
-  /* Wakeup fd used to wake pollers to check the contents of workqueue_items */
-  grpc_wakeup_fd workqueue_wakeup_fd;
-  grpc_closure_scheduler workqueue_scheduler;
-  /* Spinlock guarding the read end of the workqueue (must be held to pop from
-   * workqueue_items) */
-  gpr_spinlock workqueue_read_mu;
-  /* Queue of closures to be executed */
-  gpr_mpscq workqueue_items;
-  /* Count of items in workqueue_items */
-  gpr_atm workqueue_item_count;
-
   /* The fd is either closed or we relinquished control of it. In either
      cases, this indicates that the 'fd' on this structure is no longer
      valid */
@@ -157,12 +145,6 @@ struct grpc_fd {
 static void fd_global_init(void);
 static void fd_global_shutdown(void);
 
-static void workqueue_enqueue(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
-                              grpc_error *error);
-
-static const grpc_closure_scheduler_vtable workqueue_scheduler_vtable = {
-    workqueue_enqueue, workqueue_enqueue, "workqueue"};
-
 /*******************************************************************************
  * Pollset Declarations
  */
@@ -332,13 +314,6 @@ static grpc_fd *fd_create(int fd, const char *name) {
   grpc_lfev_init(&new_fd->write_closure);
   gpr_atm_no_barrier_store(&new_fd->read_notifier_pollset, (gpr_atm)NULL);
 
-  GRPC_LOG_IF_ERROR("fd_create",
-                    grpc_wakeup_fd_init(&new_fd->workqueue_wakeup_fd));
-  new_fd->workqueue_scheduler.vtable = &workqueue_scheduler_vtable;
-  new_fd->workqueue_read_mu = GPR_SPINLOCK_INITIALIZER;
-  gpr_mpscq_init(&new_fd->workqueue_items);
-  gpr_atm_no_barrier_store(&new_fd->workqueue_item_count, 0);
-
   new_fd->freelist_next = NULL;
   new_fd->on_done_closure = NULL;
 
@@ -431,91 +406,6 @@ static void fd_notify_on_write(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
   grpc_lfev_notify_on(exec_ctx, &fd->write_closure, closure);
 }
 
-static grpc_workqueue *fd_get_workqueue(grpc_fd *fd) {
-  REF_BY(fd, 2, "return_workqueue");
-  return (grpc_workqueue *)fd;
-}
-
-#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
-static grpc_workqueue *workqueue_ref(grpc_workqueue *workqueue,
-                                     const char *file, int line,
-                                     const char *reason) {
-  if (workqueue != NULL) {
-    ref_by((grpc_fd *)workqueue, 2, file, line, reason);
-  }
-  return workqueue;
-}
-
-static void workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
-                            const char *file, int line, const char *reason) {
-  if (workqueue != NULL) {
-    unref_by(exec_ctx, (grpc_fd *)workqueue, 2, file, line, reason);
-  }
-}
-#else
-static grpc_workqueue *workqueue_ref(grpc_workqueue *workqueue) {
-  if (workqueue != NULL) {
-    ref_by((grpc_fd *)workqueue, 2);
-  }
-  return workqueue;
-}
-
-static void workqueue_unref(grpc_exec_ctx *exec_ctx,
-                            grpc_workqueue *workqueue) {
-  if (workqueue != NULL) {
-    unref_by(exec_ctx, (grpc_fd *)workqueue, 2);
-  }
-}
-#endif
-
-static void workqueue_wakeup(grpc_fd *fd) {
-  GRPC_LOG_IF_ERROR("workqueue_enqueue",
-                    grpc_wakeup_fd_wakeup(&fd->workqueue_wakeup_fd));
-}
-
-static void workqueue_enqueue(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
-                              grpc_error *error) {
-  GPR_TIMER_BEGIN("workqueue.enqueue", 0);
-  grpc_fd *fd = (grpc_fd *)(((char *)closure->scheduler) -
-                            offsetof(grpc_fd, workqueue_scheduler));
-  REF_BY(fd, 2, "workqueue_enqueue");
-  gpr_atm last = gpr_atm_no_barrier_fetch_add(&fd->workqueue_item_count, 1);
-  closure->error_data.error = error;
-  gpr_mpscq_push(&fd->workqueue_items, &closure->next_data.atm_next);
-  if (last == 0) {
-    workqueue_wakeup(fd);
-  }
-  UNREF_BY(exec_ctx, fd, 2, "workqueue_enqueue");
-}
-
-static void fd_invoke_workqueue(grpc_exec_ctx *exec_ctx, grpc_fd *fd) {
-  /* handle spurious wakeups */
-  if (!gpr_spinlock_trylock(&fd->workqueue_read_mu)) return;
-  gpr_mpscq_node *n = gpr_mpscq_pop(&fd->workqueue_items);
-  gpr_spinlock_unlock(&fd->workqueue_read_mu);
-  if (n != NULL) {
-    if (gpr_atm_full_fetch_add(&fd->workqueue_item_count, -1) > 1) {
-      workqueue_wakeup(fd);
-    }
-    grpc_closure *c = (grpc_closure *)n;
-    grpc_error *error = c->error_data.error;
-#ifndef NDEBUG
-    c->scheduled = false;
-#endif
-    c->cb(exec_ctx, c->cb_arg, error);
-    GRPC_ERROR_UNREF(error);
-  } else if (gpr_atm_no_barrier_load(&fd->workqueue_item_count) > 0) {
-    /* n == NULL might mean there's work but it's not available to be popped
-     * yet - try to ensure another workqueue wakes up to check shortly if so
-     */
-    workqueue_wakeup(fd);
-  }
-}
-
-static grpc_closure_scheduler *workqueue_scheduler(grpc_workqueue *workqueue) {
-  return &((grpc_fd *)workqueue)->workqueue_scheduler;
-}
-
 /*******************************************************************************
  * Pollable Definitions
  */
@@ -581,22 +471,7 @@ static grpc_error *pollable_add_fd(pollable *p, grpc_fd *fd) {
       .data.ptr = fd};
   if (epoll_ctl(epfd, EPOLL_CTL_ADD, fd->fd, &ev_fd) != 0) {
     switch (errno) {
-      case EEXIST: /* if this fd is already in the epoll set, the workqueue fd
-                      must also be - just return */
-        gpr_mu_unlock(&fd->orphaned_mu);
-        return GRPC_ERROR_NONE;
-      default:
-        append_error(&error, GRPC_OS_ERROR(errno, "epoll_ctl"), err_desc);
-    }
-  }
-  struct epoll_event ev_wq = {
-      .events = (uint32_t)(EPOLLET | EPOLLIN | EPOLLEXCLUSIVE),
-      .data.ptr = (void *)(1 + (intptr_t)fd)};
-  if (epoll_ctl(epfd, EPOLL_CTL_ADD, fd->workqueue_wakeup_fd.read_fd, &ev_wq) !=
-      0) {
-    switch (errno) {
-      case EEXIST: /* if the workqueue fd is already in the epoll set we're ok
-                      - no need to do anything special */
+      case EEXIST:
         break;
       default:
         append_error(&error, GRPC_OS_ERROR(errno, "epoll_ctl"), err_desc);
@@ -859,29 +734,21 @@ static grpc_error *pollset_epoll(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
       }
       append_error(&error, grpc_wakeup_fd_consume_wakeup(&p->wakeup), err_desc);
     } else {
-      grpc_fd *fd = (grpc_fd *)(((intptr_t)data_ptr) & ~(intptr_t)1);
-      bool is_workqueue = (((intptr_t)data_ptr) & 1) != 0;
+      grpc_fd *fd = (grpc_fd *)data_ptr;
       bool cancel = (events[i].events & (EPOLLERR | EPOLLHUP)) != 0;
       bool read_ev = (events[i].events & (EPOLLIN | EPOLLPRI)) != 0;
       bool write_ev = (events[i].events & EPOLLOUT) != 0;
       if (GRPC_TRACER_ON(grpc_polling_trace)) {
         gpr_log(GPR_DEBUG,
-                "PS:%p poll %p got fd %p: is_wq=%d cancel=%d read=%d "
+                "PS:%p poll %p got fd %p: cancel=%d read=%d "
                 "write=%d",
-                pollset, p, fd, is_workqueue, cancel, read_ev, write_ev);
+                pollset, p, fd, cancel, read_ev, write_ev);
       }
-      if (is_workqueue) {
-        append_error(&error,
-                     grpc_wakeup_fd_consume_wakeup(&fd->workqueue_wakeup_fd),
-                     err_desc);
-        fd_invoke_workqueue(exec_ctx, fd);
-      } else {
-        if (read_ev || cancel) {
-          fd_become_readable(exec_ctx, fd, pollset);
-        }
-        if (write_ev || cancel) {
-          fd_become_writable(exec_ctx, fd);
-        }
+      if (read_ev || cancel) {
+        fd_become_readable(exec_ctx, fd, pollset);
+      }
+      if (write_ev || cancel) {
+        fd_become_writable(exec_ctx, fd);
       }
     }
   }
@@ -1434,7 +1301,6 @@ static const grpc_event_engine_vtable vtable = {
     .fd_notify_on_read = fd_notify_on_read,
     .fd_notify_on_write = fd_notify_on_write,
     .fd_get_read_notifier_pollset = fd_get_read_notifier_pollset,
-    .fd_get_workqueue = fd_get_workqueue,
 
     .pollset_init = pollset_init,
     .pollset_shutdown = pollset_shutdown,
@@ -1452,10 +1318,6 @@ static const grpc_event_engine_vtable vtable = {
     .pollset_set_add_fd = pollset_set_add_fd,
     .pollset_set_del_fd = pollset_set_del_fd,
 
-    .workqueue_ref = workqueue_ref,
-    .workqueue_unref = workqueue_unref,
-    .workqueue_scheduler = workqueue_scheduler,
-
     .shutdown_engine = shutdown_engine,
 };
 

src/core/lib/iomgr/ev_epollsig_linux.c

@@ -44,7 +44,6 @@
 #include "src/core/lib/iomgr/lockfree_event.h"
 #include "src/core/lib/iomgr/timer.h"
 #include "src/core/lib/iomgr/wakeup_fd_posix.h"
-#include "src/core/lib/iomgr/workqueue.h"
 #include "src/core/lib/profiling/timers.h"
 #include "src/core/lib/support/block_annotate.h"
 
@@ -162,7 +161,9 @@ static void fd_global_shutdown(void);
  * Polling island Declarations
  */
 
-#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
+//#define PI_REFCOUNT_DEBUG
+
+#ifdef PI_REFCOUNT_DEBUG
 
 #define PI_ADD_REF(p, r) pi_add_ref_dbg((p), (r), __FILE__, __LINE__)
 #define PI_UNREF(exec_ctx, p, r) \
@@ -177,8 +178,6 @@ static void fd_global_shutdown(void);
 
 /* This is also used as grpc_workqueue (by directly casing it) */
 typedef struct polling_island {
-  grpc_closure_scheduler workqueue_scheduler;
-
   gpr_mu mu;
   /* Ref count. Use PI_ADD_REF() and PI_UNREF() macros to increment/decrement
      the refcount.
@@ -199,15 +198,6 @@ typedef struct polling_island {
 
   /* Number of threads currently polling on this island */
   gpr_atm poller_count;
-  /* Mutex guarding the read end of the workqueue (must be held to pop from
-   * workqueue_items) */
-  gpr_mu workqueue_read_mu;
-  /* Queue of closures to be executed */
-  gpr_mpscq workqueue_items;
-  /* Count of items in workqueue_items */
-  gpr_atm workqueue_item_count;
-  /* Wakeup fd used to wake pollers to check the contents of workqueue_items */
-  grpc_wakeup_fd workqueue_wakeup_fd;
 
   /* The fd of the underlying epoll set */
   int epoll_fd;
@@ -282,8 +272,6 @@ static __thread polling_island *g_current_thread_polling_island;
 
 /* Forward declaration */
 static void polling_island_delete(grpc_exec_ctx *exec_ctx, polling_island *pi);
-static void workqueue_enqueue(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
-                              grpc_error *error);
 
 #ifdef GRPC_TSAN
 /* Currently TSAN may incorrectly flag data races between epoll_ctl and
@@ -296,13 +284,10 @@ static void workqueue_enqueue(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
 gpr_atm g_epoll_sync;
 #endif /* defined(GRPC_TSAN) */
 
-static const grpc_closure_scheduler_vtable workqueue_scheduler_vtable = {
-    workqueue_enqueue, workqueue_enqueue, "workqueue"};
-
 static void pi_add_ref(polling_island *pi);
 static void pi_unref(grpc_exec_ctx *exec_ctx, polling_island *pi);
 
-#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
+#ifdef PI_REFCOUNT_DEBUG
 static void pi_add_ref_dbg(polling_island *pi, const char *reason,
                            const char *file, int line) {
   long old_cnt = gpr_atm_acq_load(&pi->ref_count);
@@ -318,36 +303,6 @@ static void pi_unref_dbg(grpc_exec_ctx *exec_ctx, polling_island *pi,
   gpr_log(GPR_DEBUG, "Unref pi: %p, old:%ld -> new:%ld (%s) - (%s, %d)",
           (void *)pi, old_cnt, (old_cnt - 1), reason, file, line);
 }
-
-static grpc_workqueue *workqueue_ref(grpc_workqueue *workqueue,
-                                     const char *file, int line,
-                                     const char *reason) {
-  if (workqueue != NULL) {
-    pi_add_ref_dbg((polling_island *)workqueue, reason, file, line);
-  }
-  return workqueue;
-}
-
-static void workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
-                            const char *file, int line, const char *reason) {
-  if (workqueue != NULL) {
-    pi_unref_dbg(exec_ctx, (polling_island *)workqueue, reason, file, line);
-  }
-}
-#else
-static grpc_workqueue *workqueue_ref(grpc_workqueue *workqueue) {
-  if (workqueue != NULL) {
-    pi_add_ref((polling_island *)workqueue);
-  }
-  return workqueue;
-}
-
-static void workqueue_unref(grpc_exec_ctx *exec_ctx,
-                            grpc_workqueue *workqueue) {
-  if (workqueue != NULL) {
-    pi_unref(exec_ctx, (polling_island *)workqueue);
-  }
-}
 #endif
 
 static void pi_add_ref(polling_island *pi) {
@@ -511,26 +466,16 @@ static polling_island *polling_island_create(grpc_exec_ctx *exec_ctx,
   *error = GRPC_ERROR_NONE;
 
   pi = gpr_malloc(sizeof(*pi));
-  pi->workqueue_scheduler.vtable = &workqueue_scheduler_vtable;
   gpr_mu_init(&pi->mu);
   pi->fd_cnt = 0;
   pi->fd_capacity = 0;
   pi->fds = NULL;
   pi->epoll_fd = -1;
 
-  gpr_mu_init(&pi->workqueue_read_mu);
-  gpr_mpscq_init(&pi->workqueue_items);
-  gpr_atm_rel_store(&pi->workqueue_item_count, 0);
-
   gpr_atm_rel_store(&pi->ref_count, 0);
   gpr_atm_rel_store(&pi->poller_count, 0);
   gpr_atm_rel_store(&pi->merged_to, (gpr_atm)NULL);
 
-  if (!append_error(error, grpc_wakeup_fd_init(&pi->workqueue_wakeup_fd),
-                    err_desc)) {
-    goto done;
-  }
-
   pi->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
 
   if (pi->epoll_fd < 0) {
@@ -538,8 +483,6 @@ static polling_island *polling_island_create(grpc_exec_ctx *exec_ctx,
     goto done;
   }
 
-  polling_island_add_wakeup_fd_locked(pi, &pi->workqueue_wakeup_fd, error);
-
   if (initial_fd != NULL) {
     polling_island_add_fds_locked(pi, &initial_fd, 1, true, error);
   }
@@ -558,11 +501,7 @@ static void polling_island_delete(grpc_exec_ctx *exec_ctx, polling_island *pi) {
   if (pi->epoll_fd >= 0) {
     close(pi->epoll_fd);
   }
-  GPR_ASSERT(gpr_atm_no_barrier_load(&pi->workqueue_item_count) == 0);
-  gpr_mu_destroy(&pi->workqueue_read_mu);
-  gpr_mpscq_destroy(&pi->workqueue_items);
   gpr_mu_destroy(&pi->mu);
-  grpc_wakeup_fd_destroy(&pi->workqueue_wakeup_fd);
   gpr_free(pi->fds);
   gpr_free(pi);
 }
@@ -707,45 +646,6 @@ static void polling_island_unlock_pair(polling_island *p, polling_island *q) {
   }
 }
 
-static void workqueue_maybe_wakeup(polling_island *pi) {
-  /* If this thread is the current poller, then it may be that it's about to
-     decrement the current poller count, so we need to look past this thread */
-  bool is_current_poller = (g_current_thread_polling_island == pi);
-  gpr_atm min_current_pollers_for_wakeup = is_current_poller ? 1 : 0;
-  gpr_atm current_pollers = gpr_atm_no_barrier_load(&pi->poller_count);
-  /* Only issue a wakeup if it's likely that some poller could come in and take
-     it right now. Note that since we do an anticipatory mpscq_pop every poll
-     loop, it's ok if we miss the wakeup here, as we'll get the work item when
-     the next poller enters anyway. */
-  if (current_pollers >= min_current_pollers_for_wakeup) {
-    GRPC_LOG_IF_ERROR("workqueue_wakeup_fd",
-                      grpc_wakeup_fd_wakeup(&pi->workqueue_wakeup_fd));
-  }
-}
-
-static void workqueue_move_items_to_parent(polling_island *q) {
-  polling_island *p = (polling_island *)gpr_atm_no_barrier_load(&q->merged_to);
-  if (p == NULL) {
-    return;
-  }
-  gpr_mu_lock(&q->workqueue_read_mu);
-  int num_added = 0;
-  while (gpr_atm_no_barrier_load(&q->workqueue_item_count) > 0) {
-    gpr_mpscq_node *n = gpr_mpscq_pop(&q->workqueue_items);
-    if (n != NULL) {
-      gpr_atm_no_barrier_fetch_add(&q->workqueue_item_count, -1);
-      gpr_atm_no_barrier_fetch_add(&p->workqueue_item_count, 1);
-      gpr_mpscq_push(&p->workqueue_items, n);
-      num_added++;
-    }
-  }
-  gpr_mu_unlock(&q->workqueue_read_mu);
-  if (num_added > 0) {
-    workqueue_maybe_wakeup(p);
-  }
-  workqueue_move_items_to_parent(p);
-}
-
 static polling_island *polling_island_merge(polling_island *p,
                                             polling_island *q,
                                             grpc_error **error) {
@@ -770,8 +670,6 @@ static polling_island *polling_island_merge(polling_island *p,
     /* Add the 'merged_to' link from p --> q */
     gpr_atm_rel_store(&p->merged_to, (gpr_atm)q);
     PI_ADD_REF(q, "pi_merge"); /* To account for the new incoming ref from p */
-
-    workqueue_move_items_to_parent(p);
   }
   /* else if p == q, nothing needs to be done */
 
@@ -782,32 +680,6 @@ static polling_island *polling_island_merge(polling_island *p,
   return q;
 }
 
-static void workqueue_enqueue(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
-                              grpc_error *error) {
-  GPR_TIMER_BEGIN("workqueue.enqueue", 0);
-  grpc_workqueue *workqueue = (grpc_workqueue *)closure->scheduler;
-  /* take a ref to the workqueue: otherwise it can happen that whatever events
-   * this kicks off ends up destroying the workqueue before this function
-   * completes */
-  GRPC_WORKQUEUE_REF(workqueue, "enqueue");
-  polling_island *pi = (polling_island *)workqueue;
-  gpr_atm last = gpr_atm_no_barrier_fetch_add(&pi->workqueue_item_count, 1);
-  closure->error_data.error = error;
-  gpr_mpscq_push(&pi->workqueue_items, &closure->next_data.atm_next);
-  if (last == 0) {
-    workqueue_maybe_wakeup(pi);
-  }
-  workqueue_move_items_to_parent(pi);
-  GRPC_WORKQUEUE_UNREF(exec_ctx, workqueue, "enqueue");
-  GPR_TIMER_END("workqueue.enqueue", 0);
-}
-
-static grpc_closure_scheduler *workqueue_scheduler(grpc_workqueue *workqueue) {
-  polling_island *pi = (polling_island *)workqueue;
-  return workqueue == NULL ? grpc_schedule_on_exec_ctx
-                           : &pi->workqueue_scheduler;
-}
-
 static grpc_error *polling_island_global_init() {
   grpc_error *error = GRPC_ERROR_NONE;
 
@@ -1069,14 +941,6 @@ static void fd_notify_on_write(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
   grpc_lfev_notify_on(exec_ctx, &fd->write_closure, closure);
 }
 
-static grpc_workqueue *fd_get_workqueue(grpc_fd *fd) {
-  gpr_mu_lock(&fd->po.mu);
-  grpc_workqueue *workqueue =
-      GRPC_WORKQUEUE_REF((grpc_workqueue *)fd->po.pi, "fd_get_workqueue");
-  gpr_mu_unlock(&fd->po.mu);
-  return workqueue;
-}
-
 /*******************************************************************************
  * Pollset Definitions
  */
@@ -1314,44 +1178,6 @@ static void pollset_destroy(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset) {
   gpr_mu_destroy(&pollset->po.mu);
 }
 
-static bool maybe_do_workqueue_work(grpc_exec_ctx *exec_ctx,
-                                    polling_island *pi) {
-  if (gpr_mu_trylock(&pi->workqueue_read_mu)) {
-    gpr_mpscq_node *n = gpr_mpscq_pop(&pi->workqueue_items);
-    gpr_mu_unlock(&pi->workqueue_read_mu);
-    if (n != NULL) {
-      gpr_atm remaining =
-          gpr_atm_full_fetch_add(&pi->workqueue_item_count, -1) - 1;
-      GRPC_POLLING_TRACE(
-          "maybe_do_workqueue_work: pi: %p: got closure %p, remaining = "
-          "%" PRIdPTR,
-          pi, n, remaining);
-      if (remaining > 0) {
-        workqueue_maybe_wakeup(pi);
-      }
-      grpc_closure *c = (grpc_closure *)n;
-      grpc_error *error = c->error_data.error;
-#ifndef NDEBUG
-      c->scheduled = false;
-#endif
-      c->cb(exec_ctx, c->cb_arg, error);
-      GRPC_ERROR_UNREF(error);
-      return true;
-    } else if (gpr_atm_no_barrier_load(&pi->workqueue_item_count) > 0) {
-      /* n == NULL might mean there's work but it's not available to be popped
-       * yet - try to ensure another workqueue wakes up to check shortly if so
-       */
-      GRPC_POLLING_TRACE(
-          "maybe_do_workqueue_work: pi: %p: more to do, but not yet", pi);
-      workqueue_maybe_wakeup(pi);
-    }
-  } else {
-    GRPC_POLLING_TRACE("maybe_do_workqueue_work: pi: %p: read already locked",
-                       pi);
-  }
-  return false;
-}
-
 #define GRPC_EPOLL_MAX_EVENTS 100
 /* Note: sig_mask contains the signal mask to use *during* epoll_wait() */
 static void pollset_work_and_unlock(grpc_exec_ctx *exec_ctx,
@@ -1407,76 +1233,61 @@ static void pollset_work_and_unlock(grpc_exec_ctx *exec_ctx,
   PI_ADD_REF(pi, "ps_work");
   gpr_mu_unlock(&pollset->po.mu);
 
-  /* If we get some workqueue work to do, it might end up completing an item on
-     the completion queue, so there's no need to poll... so we skip that and
-     redo the complete loop to verify */
-  GRPC_POLLING_TRACE("pollset_work: pollset: %p, worker %p, pi %p", pollset,
-                     worker, pi);
-  if (!maybe_do_workqueue_work(exec_ctx, pi)) {
-    GRPC_POLLING_TRACE("pollset_work: begins");
-    gpr_atm_no_barrier_fetch_add(&pi->poller_count, 1);
-    g_current_thread_polling_island = pi;
-
-    GRPC_SCHEDULING_START_BLOCKING_REGION;
-    ep_rv = epoll_pwait(epoll_fd, ep_ev, GRPC_EPOLL_MAX_EVENTS, timeout_ms,
-                        sig_mask);
-    GRPC_SCHEDULING_END_BLOCKING_REGION;
-    if (ep_rv < 0) {
-      if (errno != EINTR) {
-        gpr_asprintf(&err_msg,
-                     "epoll_wait() epoll fd: %d failed with error: %d (%s)",
-                     epoll_fd, errno, strerror(errno));
-        append_error(error, GRPC_OS_ERROR(errno, err_msg), err_desc);
-      } else {
-        /* We were interrupted. Save an interation by doing a zero timeout
-           epoll_wait to see if there are any other events of interest */
-        GRPC_POLLING_TRACE(
-            "pollset_work: pollset: %p, worker: %p received kick",
-            (void *)pollset, (void *)worker);
-        ep_rv = epoll_wait(epoll_fd, ep_ev, GRPC_EPOLL_MAX_EVENTS, 0);
-      }
+  gpr_atm_no_barrier_fetch_add(&pi->poller_count, 1);
+  g_current_thread_polling_island = pi;
+
+  GRPC_SCHEDULING_START_BLOCKING_REGION;
+  ep_rv =
+      epoll_pwait(epoll_fd, ep_ev, GRPC_EPOLL_MAX_EVENTS, timeout_ms, sig_mask);
+  GRPC_SCHEDULING_END_BLOCKING_REGION;
+  if (ep_rv < 0) {
+    if (errno != EINTR) {
+      gpr_asprintf(&err_msg,
+                   "epoll_wait() epoll fd: %d failed with error: %d (%s)",
+                   epoll_fd, errno, strerror(errno));
+      append_error(error, GRPC_OS_ERROR(errno, err_msg), err_desc);
+    } else {
+      /* We were interrupted. Save an interation by doing a zero timeout
+         epoll_wait to see if there are any other events of interest */
+      GRPC_POLLING_TRACE("pollset_work: pollset: %p, worker: %p received kick",
+                         (void *)pollset, (void *)worker);
+      ep_rv = epoll_wait(epoll_fd, ep_ev, GRPC_EPOLL_MAX_EVENTS, 0);
     }
+  }
 
 #ifdef GRPC_TSAN
-    /* See the definition of g_poll_sync for more details */
-    gpr_atm_acq_load(&g_epoll_sync);
+  /* See the definition of g_poll_sync for more details */
+  gpr_atm_acq_load(&g_epoll_sync);
 #endif /* defined(GRPC_TSAN) */
 
-    for (int i = 0; i < ep_rv; ++i) {
-      void *data_ptr = ep_ev[i].data.ptr;
-      if (data_ptr == &pi->workqueue_wakeup_fd) {
-        append_error(error,
-                     grpc_wakeup_fd_consume_wakeup(&pi->workqueue_wakeup_fd),
-                     err_desc);
-        maybe_do_workqueue_work(exec_ctx, pi);
-      } else if (data_ptr == &polling_island_wakeup_fd) {
-        GRPC_POLLING_TRACE(
-            "pollset_work: pollset: %p, worker: %p polling island (epoll_fd: "
-            "%d) got merged",
-            (void *)pollset, (void *)worker, epoll_fd);
-        /* This means that our polling island is merged with a different
-           island. We do not have to do anything here since the subsequent call
-           to the function pollset_work_and_unlock() will pick up the correct
-           epoll_fd */
-      } else {
-        grpc_fd *fd = data_ptr;
-        int cancel = ep_ev[i].events & (EPOLLERR | EPOLLHUP);
-        int read_ev = ep_ev[i].events & (EPOLLIN | EPOLLPRI);
-        int write_ev = ep_ev[i].events & EPOLLOUT;
-        if (read_ev || cancel) {
-          fd_become_readable(exec_ctx, fd, pollset);
-        }
-        if (write_ev || cancel) {
-          fd_become_writable(exec_ctx, fd);
-        }
+  for (int i = 0; i < ep_rv; ++i) {
+    void *data_ptr = ep_ev[i].data.ptr;
+    if (data_ptr == &polling_island_wakeup_fd) {
+      GRPC_POLLING_TRACE(
+          "pollset_work: pollset: %p, worker: %p polling island (epoll_fd: "
+          "%d) got merged",
+          (void *)pollset, (void *)worker, epoll_fd);
+      /* This means that our polling island is merged with a different
+         island. We do not have to do anything here since the subsequent call
+         to the function pollset_work_and_unlock() will pick up the correct
+         epoll_fd */
+    } else {
+      grpc_fd *fd = data_ptr;
+      int cancel = ep_ev[i].events & (EPOLLERR | EPOLLHUP);
+      int read_ev = ep_ev[i].events & (EPOLLIN | EPOLLPRI);
+      int write_ev = ep_ev[i].events & EPOLLOUT;
+      if (read_ev || cancel) {
+        fd_become_readable(exec_ctx, fd, pollset);
+      }
+      if (write_ev || cancel) {
+        fd_become_writable(exec_ctx, fd);
       }
     }
-
-    g_current_thread_polling_island = NULL;
-    gpr_atm_no_barrier_fetch_add(&pi->poller_count, -1);
-    GRPC_POLLING_TRACE("pollset_work: ends");
   }
 
+  g_current_thread_polling_island = NULL;
+  gpr_atm_no_barrier_fetch_add(&pi->poller_count, -1);
+
   GPR_ASSERT(pi != NULL);
 
   /* Before leaving, release the extra ref we added to the polling island. It
@@ -1867,7 +1678,6 @@ static const grpc_event_engine_vtable vtable = {
     .fd_notify_on_read = fd_notify_on_read,
     .fd_notify_on_write = fd_notify_on_write,
     .fd_get_read_notifier_pollset = fd_get_read_notifier_pollset,
-    .fd_get_workqueue = fd_get_workqueue,
 
     .pollset_init = pollset_init,
     .pollset_shutdown = pollset_shutdown,
@@ -1885,10 +1695,6 @@ static const grpc_event_engine_vtable vtable = {
     .pollset_set_add_fd = pollset_set_add_fd,
     .pollset_set_del_fd = pollset_set_del_fd,
 
-    .workqueue_ref = workqueue_ref,
-    .workqueue_unref = workqueue_unref,
-    .workqueue_scheduler = workqueue_scheduler,
-
     .shutdown_engine = shutdown_engine,
 };
 

src/core/lib/iomgr/ev_poll_posix.c

@@ -633,8 +633,6 @@ static void fd_end_poll(grpc_exec_ctx *exec_ctx, grpc_fd_watcher *watcher,
   GRPC_FD_UNREF(fd, "poll");
 }
 
-static grpc_workqueue *fd_get_workqueue(grpc_fd *fd) { return NULL; }
-
 /*******************************************************************************
  * pollset_posix.c
  */
@@ -1273,30 +1271,6 @@ static void pollset_set_del_fd(grpc_exec_ctx *exec_ctx,
   gpr_mu_unlock(&pollset_set->mu);
 }
 
-/*******************************************************************************
- * workqueue stubs
- */
-
-#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
-static grpc_workqueue *workqueue_ref(grpc_workqueue *workqueue,
-                                     const char *file, int line,
-                                     const char *reason) {
-  return workqueue;
-}
-static void workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
-                            const char *file, int line, const char *reason) {}
-#else
-static grpc_workqueue *workqueue_ref(grpc_workqueue *workqueue) {
-  return workqueue;
-}
-static void workqueue_unref(grpc_exec_ctx *exec_ctx,
-                            grpc_workqueue *workqueue) {}
-#endif
-
-static grpc_closure_scheduler *workqueue_scheduler(grpc_workqueue *workqueue) {
-  return grpc_schedule_on_exec_ctx;
-}
-
 /*******************************************************************************
  * Condition Variable polling extensions
  */
@@ -1514,7 +1488,6 @@ static const grpc_event_engine_vtable vtable = {
     .fd_notify_on_read = fd_notify_on_read,
     .fd_notify_on_write = fd_notify_on_write,
     .fd_get_read_notifier_pollset = fd_get_read_notifier_pollset,
-    .fd_get_workqueue = fd_get_workqueue,
 
     .pollset_init = pollset_init,
     .pollset_shutdown = pollset_shutdown,
@@ -1532,10 +1505,6 @@ static const grpc_event_engine_vtable vtable = {
     .pollset_set_add_fd = pollset_set_add_fd,
     .pollset_set_del_fd = pollset_set_del_fd,
 
-    .workqueue_ref = workqueue_ref,
-    .workqueue_unref = workqueue_unref,
-    .workqueue_scheduler = workqueue_scheduler,
-
     .shutdown_engine = shutdown_engine,
 };
 

src/core/lib/iomgr/ev_posix.c

@@ -156,10 +156,6 @@ grpc_fd *grpc_fd_create(int fd, const char *name) {
   return g_event_engine->fd_create(fd, name);
 }
 
-grpc_workqueue *grpc_fd_get_workqueue(grpc_fd *fd) {
-  return g_event_engine->fd_get_workqueue(fd);
-}
-
 int grpc_fd_wrapped_fd(grpc_fd *fd) {
   return g_event_engine->fd_wrapped_fd(fd);
 }
@@ -261,26 +257,4 @@ void grpc_pollset_set_del_fd(grpc_exec_ctx *exec_ctx,
   g_event_engine->pollset_set_del_fd(exec_ctx, pollset_set, fd);
 }
 
-#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
-grpc_workqueue *grpc_workqueue_ref(grpc_workqueue *workqueue, const char *file,
-                                   int line, const char *reason) {
-  return g_event_engine->workqueue_ref(workqueue, file, line, reason);
-}
-void grpc_workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
-                          const char *file, int line, const char *reason) {
-  g_event_engine->workqueue_unref(exec_ctx, workqueue, file, line, reason);
-}
-#else
-grpc_workqueue *grpc_workqueue_ref(grpc_workqueue *workqueue) {
-  return g_event_engine->workqueue_ref(workqueue);
-}
-void grpc_workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue) {
-  g_event_engine->workqueue_unref(exec_ctx, workqueue);
-}
-#endif
-
-grpc_closure_scheduler *grpc_workqueue_scheduler(grpc_workqueue *workqueue) {
-  return g_event_engine->workqueue_scheduler(workqueue);
-}
-
 #endif  // GRPC_POSIX_SOCKET

src/core/lib/iomgr/ev_posix.h

@@ -26,7 +26,6 @@
 #include "src/core/lib/iomgr/pollset.h"
 #include "src/core/lib/iomgr/pollset_set.h"
 #include "src/core/lib/iomgr/wakeup_fd_posix.h"
-#include "src/core/lib/iomgr/workqueue.h"
 
 extern grpc_tracer_flag grpc_polling_trace; /* Disabled by default */
 
@@ -45,7 +44,6 @@ typedef struct grpc_event_engine_vtable {
   void (*fd_notify_on_write)(grpc_exec_ctx *exec_ctx, grpc_fd *fd,
                              grpc_closure *closure);
   bool (*fd_is_shutdown)(grpc_fd *fd);
-  grpc_workqueue *(*fd_get_workqueue)(grpc_fd *fd);
   grpc_pollset *(*fd_get_read_notifier_pollset)(grpc_exec_ctx *exec_ctx,
                                                 grpc_fd *fd);
 
@@ -82,17 +80,6 @@ typedef struct grpc_event_engine_vtable {
                              grpc_pollset_set *pollset_set, grpc_fd *fd);
 
   void (*shutdown_engine)(void);
-
-#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
-  grpc_workqueue *(*workqueue_ref)(grpc_workqueue *workqueue, const char *file,
-                                   int line, const char *reason);
-  void (*workqueue_unref)(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
-                          const char *file, int line, const char *reason);
-#else
-  grpc_workqueue *(*workqueue_ref)(grpc_workqueue *workqueue);
-  void (*workqueue_unref)(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue);
-#endif
-  grpc_closure_scheduler *(*workqueue_scheduler)(grpc_workqueue *workqueue);
 } grpc_event_engine_vtable;
 
 void grpc_event_engine_init(void);
@@ -106,9 +93,6 @@ const char *grpc_get_poll_strategy_name();
    This takes ownership of closing fd. */
 grpc_fd *grpc_fd_create(int fd, const char *name);
 
-/* Get a workqueue that's associated with this fd */
-grpc_workqueue *grpc_fd_get_workqueue(grpc_fd *fd);
-
 /* Return the wrapped fd, or -1 if it has been released or closed. */
 int grpc_fd_wrapped_fd(grpc_fd *fd);
 

src/core/lib/iomgr/exec_ctx.c

@@ -23,7 +23,6 @@
 #include <grpc/support/thd.h>
 
 #include "src/core/lib/iomgr/combiner.h"
-#include "src/core/lib/iomgr/workqueue.h"
 #include "src/core/lib/profiling/timers.h"
 
 bool grpc_exec_ctx_ready_to_finish(grpc_exec_ctx *exec_ctx) {

src/core/lib/iomgr/executor.c

@@ -21,132 +21,172 @@
 #include <string.h>
 
 #include <grpc/support/alloc.h>
+#include <grpc/support/cpu.h>
 #include <grpc/support/log.h>
 #include <grpc/support/sync.h>
 #include <grpc/support/thd.h>
+#include <grpc/support/tls.h>
+#include <grpc/support/useful.h>
+
 #include "src/core/lib/iomgr/exec_ctx.h"
+#include "src/core/lib/support/spinlock.h"
+
+#define MAX_DEPTH 2
 
-typedef struct grpc_executor_data {
-  int busy;          /**< is the thread currently running? */
-  int shutting_down; /**< has \a grpc_shutdown() been invoked? */
-  int pending_join;  /**< has the thread finished but not been joined? */
-  grpc_closure_list closures; /**< collection of pending work */
-  gpr_thd_id tid; /**< thread id of the thread, only valid if \a busy or \a
-                     pending_join are true */
-  gpr_thd_options options;
+typedef struct {
   gpr_mu mu;
-} grpc_executor;
+  gpr_cv cv;
+  grpc_closure_list elems;
+  size_t depth;
+  bool shutdown;
+  gpr_thd_id id;
+} thread_state;
 
-static grpc_executor g_executor;
+static thread_state *g_thread_state;
+static size_t g_max_threads;
+static gpr_atm g_cur_threads;
+static gpr_spinlock g_adding_thread_lock = GPR_SPINLOCK_STATIC_INITIALIZER;
 
-void grpc_executor_init() {
-  memset(&g_executor, 0, sizeof(grpc_executor));
-  gpr_mu_init(&g_executor.mu);
-  g_executor.options = gpr_thd_options_default();
-  gpr_thd_options_set_joinable(&g_executor.options);
-}
+GPR_TLS_DECL(g_this_thread_state);
 
-/* thread body */
-static void closure_exec_thread_func(void *ignored) {
-  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-  while (1) {
-    gpr_mu_lock(&g_executor.mu);
-    if (g_executor.shutting_down != 0) {
-      gpr_mu_unlock(&g_executor.mu);
-      break;
-    }
-    if (grpc_closure_list_empty(g_executor.closures)) {
-      /* no more work, time to die */
-      GPR_ASSERT(g_executor.busy == 1);
-      g_executor.busy = 0;
-      gpr_mu_unlock(&g_executor.mu);
-      break;
-    } else {
-      grpc_closure *c = g_executor.closures.head;
-      grpc_closure_list_init(&g_executor.closures);
-      gpr_mu_unlock(&g_executor.mu);
-      while (c != NULL) {
-        grpc_closure *next = c->next_data.next;
-        grpc_error *error = c->error_data.error;
+static void executor_thread(void *arg);
+
+static size_t run_closures(grpc_exec_ctx *exec_ctx, grpc_closure_list list) {
+  size_t n = 0;
+
+  grpc_closure *c = list.head;
+  while (c != NULL) {
+    grpc_closure *next = c->next_data.next;
+    grpc_error *error = c->error_data.error;
 #ifndef NDEBUG
-        c->scheduled = false;
+    c->scheduled = false;
 #endif
-        c->cb(&exec_ctx, c->cb_arg, error);
-        GRPC_ERROR_UNREF(error);
-        c = next;
-      }
-      grpc_exec_ctx_flush(&exec_ctx);
-    }
+    c->cb(exec_ctx, c->cb_arg, error);
+    GRPC_ERROR_UNREF(error);
+    c = next;
+    n++;
   }
-  grpc_exec_ctx_finish(&exec_ctx);
+
+  return n;
 }
 
-/* Spawn the thread if new work has arrived a no thread is up */
-static void maybe_spawn_locked() {
-  if (grpc_closure_list_empty(g_executor.closures) == 1) {
-    return;
-  }
-  if (g_executor.shutting_down == 1) {
-    return;
-  }
+bool grpc_executor_is_threaded() {
+  return gpr_atm_no_barrier_load(&g_cur_threads) > 0;
+}
 
-  if (g_executor.busy != 0) {
-    /* Thread still working. New work will be picked up by already running
-     * thread. Not spawning anything. */
-    return;
-  } else if (g_executor.pending_join != 0) {
-    /* Pickup the remains of the previous incarnations of the thread. */
-    gpr_thd_join(g_executor.tid);
-    g_executor.pending_join = 0;
+void grpc_executor_set_threading(grpc_exec_ctx *exec_ctx, bool threading) {
+  gpr_atm cur_threads = gpr_atm_no_barrier_load(&g_cur_threads);
+  if (threading) {
+    if (cur_threads > 0) return;
+    g_max_threads = GPR_MAX(1, 2 * gpr_cpu_num_cores());
+    gpr_atm_no_barrier_store(&g_cur_threads, 1);
+    gpr_tls_init(&g_this_thread_state);
+    g_thread_state = gpr_zalloc(sizeof(thread_state) * g_max_threads);
+    for (size_t i = 0; i < g_max_threads; i++) {
+      gpr_mu_init(&g_thread_state[i].mu);
+      gpr_cv_init(&g_thread_state[i].cv);
+      g_thread_state[i].elems = (grpc_closure_list)GRPC_CLOSURE_LIST_INIT;
+    }
+
+    gpr_thd_options opt = gpr_thd_options_default();
+    gpr_thd_options_set_joinable(&opt);
+    gpr_thd_new(&g_thread_state[0].id, executor_thread, &g_thread_state[0],
+                &opt);
+  } else {
+    if (cur_threads == 0) return;
+    for (size_t i = 0; i < g_max_threads; i++) {
+      gpr_mu_lock(&g_thread_state[i].mu);
+      g_thread_state[i].shutdown = true;
+      gpr_cv_signal(&g_thread_state[i].cv);
+      gpr_mu_unlock(&g_thread_state[i].mu);
+    }
+    /* ensure no thread is adding a new thread... once this is past, then
+       no thread will try to add a new one either (since shutdown is true) */
+    gpr_spinlock_lock(&g_adding_thread_lock);
+    gpr_spinlock_unlock(&g_adding_thread_lock);
+    for (gpr_atm i = 0; i < g_cur_threads; i++) {
+      gpr_thd_join(g_thread_state[i].id);
+    }
+    gpr_atm_no_barrier_store(&g_cur_threads, 0);
+    for (size_t i = 0; i < g_max_threads; i++) {
+      gpr_mu_destroy(&g_thread_state[i].mu);
+      gpr_cv_destroy(&g_thread_state[i].cv);
+      run_closures(exec_ctx, g_thread_state[i].elems);
+    }
+    gpr_free(g_thread_state);
+    gpr_tls_destroy(&g_this_thread_state);
   }
+}
 
-  /* All previous instances of the thread should have been joined at this point.
-   * Spawn time! */
-  g_executor.busy = 1;
-  GPR_ASSERT(gpr_thd_new(&g_executor.tid, closure_exec_thread_func, NULL,
-                         &g_executor.options));
-  g_executor.pending_join = 1;
+void grpc_executor_init(grpc_exec_ctx *exec_ctx) {
+  gpr_atm_no_barrier_store(&g_cur_threads, 0);
+  grpc_executor_set_threading(exec_ctx, true);
 }
 
-static void executor_push(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
-                          grpc_error *error) {
-  gpr_mu_lock(&g_executor.mu);
-  if (g_executor.shutting_down == 0) {
-    grpc_closure_list_append(&g_executor.closures, closure, error);
-    maybe_spawn_locked();
+void grpc_executor_shutdown(grpc_exec_ctx *exec_ctx) {
+  grpc_executor_set_threading(exec_ctx, false);
+}
+
+static void executor_thread(void *arg) {
+  thread_state *ts = arg;
+  gpr_tls_set(&g_this_thread_state, (intptr_t)ts);
+
+  grpc_exec_ctx exec_ctx =
+      GRPC_EXEC_CTX_INITIALIZER(0, grpc_never_ready_to_finish, NULL);
+
+  size_t subtract_depth = 0;
+  for (;;) {
+    gpr_mu_lock(&ts->mu);
+    ts->depth -= subtract_depth;
+    while (grpc_closure_list_empty(ts->elems) && !ts->shutdown) {
+      gpr_cv_wait(&ts->cv, &ts->mu, gpr_inf_future(GPR_CLOCK_REALTIME));
+    }
+    if (ts->shutdown) {
+      gpr_mu_unlock(&ts->mu);
+      break;
+    }
+    grpc_closure_list exec = ts->elems;
+    ts->elems = (grpc_closure_list)GRPC_CLOSURE_LIST_INIT;
+    gpr_mu_unlock(&ts->mu);
+
+    subtract_depth = run_closures(&exec_ctx, exec);
+    grpc_exec_ctx_flush(&exec_ctx);
   }
-  gpr_mu_unlock(&g_executor.mu);
+  grpc_exec_ctx_finish(&exec_ctx);
 }
 
-void grpc_executor_shutdown(grpc_exec_ctx *exec_ctx) {
-  int pending_join;
-
-  gpr_mu_lock(&g_executor.mu);
-  pending_join = g_executor.pending_join;
-  g_executor.shutting_down = 1;
-  gpr_mu_unlock(&g_executor.mu);
-  /* we can release the lock at this point despite the access to the closure
-   * list below because we aren't accepting new work */
-
-  /* Execute pending callbacks, some may be performing cleanups */
-  grpc_closure *c = g_executor.closures.head;
-  grpc_closure_list_init(&g_executor.closures);
-  while (c != NULL) {
-    grpc_closure *next = c->next_data.next;
-    grpc_error *error = c->error_data.error;
-#ifndef NDEBUG
-    c->scheduled = false;
-#endif
-    c->cb(exec_ctx, c->cb_arg, error);
-    GRPC_ERROR_UNREF(error);
-    c = next;
+static void executor_push(grpc_exec_ctx *exec_ctx, grpc_closure *closure,
+                          grpc_error *error) {
+  size_t cur_thread_count = (size_t)gpr_atm_no_barrier_load(&g_cur_threads);
+  if (cur_thread_count == 0) {
+    grpc_closure_list_append(&exec_ctx->closure_list, closure, error);
+    return;
+  }
+  thread_state *ts = (thread_state *)gpr_tls_get(&g_this_thread_state);
+  if (ts == NULL) {
+    ts = &g_thread_state[GPR_HASH_POINTER(exec_ctx, cur_thread_count)];
   }
-  grpc_exec_ctx_flush(exec_ctx);
-  GPR_ASSERT(grpc_closure_list_empty(g_executor.closures));
-  if (pending_join) {
-    gpr_thd_join(g_executor.tid);
+  gpr_mu_lock(&ts->mu);
+  if (grpc_closure_list_empty(ts->elems)) {
+    gpr_cv_signal(&ts->cv);
+  }
+  grpc_closure_list_append(&ts->elems, closure, error);
+  ts->depth++;
+  bool try_new_thread = ts->depth > MAX_DEPTH &&
+                        cur_thread_count < g_max_threads && !ts->shutdown;
+  gpr_mu_unlock(&ts->mu);
+  if (try_new_thread && gpr_spinlock_trylock(&g_adding_thread_lock)) {
+    cur_thread_count = (size_t)gpr_atm_no_barrier_load(&g_cur_threads);
+    if (cur_thread_count < g_max_threads) {
+      gpr_atm_no_barrier_store(&g_cur_threads, cur_thread_count + 1);
+
+      gpr_thd_options opt = gpr_thd_options_default();
+      gpr_thd_options_set_joinable(&opt);
+      gpr_thd_new(&g_thread_state[cur_thread_count].id, executor_thread,
+                  &g_thread_state[cur_thread_count], &opt);
+    }
+    gpr_spinlock_unlock(&g_adding_thread_lock);
   }
-  gpr_mu_destroy(&g_executor.mu);
 }
 
 static const grpc_closure_scheduler_vtable executor_vtable = {

src/core/lib/iomgr/executor.h

@@ -26,11 +26,18 @@
  * This mechanism is meant to outsource work (grpc_closure instances) to a
  * thread, for those cases where blocking isn't an option but there isn't a
  * non-blocking solution available. */
-void grpc_executor_init();
+void grpc_executor_init(grpc_exec_ctx *exec_ctx);
 
 extern grpc_closure_scheduler *grpc_executor_scheduler;
 
 /** Shutdown the executor, running all pending work as part of the call */
 void grpc_executor_shutdown(grpc_exec_ctx *exec_ctx);
 
+/** Is the executor multi-threaded? */
+bool grpc_executor_is_threaded();
+
+/* enable/disable threading - must be called after grpc_executor_init and before
+   grpc_executor_shutdown */
+void grpc_executor_set_threading(grpc_exec_ctx *exec_ctx, bool enable);
+
 #endif /* GRPC_CORE_LIB_IOMGR_EXECUTOR_H */

src/core/lib/iomgr/iomgr.c

@@ -29,6 +29,7 @@
 #include <grpc/support/useful.h>
 
 #include "src/core/lib/iomgr/exec_ctx.h"
+#include "src/core/lib/iomgr/executor.h"
 #include "src/core/lib/iomgr/iomgr_internal.h"
 #include "src/core/lib/iomgr/network_status_tracker.h"
 #include "src/core/lib/iomgr/timer.h"
@@ -41,11 +42,12 @@ static gpr_cv g_rcv;
 static int g_shutdown;
 static grpc_iomgr_object g_root_object;
 
-void grpc_iomgr_init(void) {
+void grpc_iomgr_init(grpc_exec_ctx *exec_ctx) {
   g_shutdown = 0;
   gpr_mu_init(&g_mu);
   gpr_cv_init(&g_rcv);
   grpc_exec_ctx_global_init();
+  grpc_executor_init(exec_ctx);
   grpc_timer_list_init(gpr_now(GPR_CLOCK_MONOTONIC));
   g_root_object.next = g_root_object.prev = &g_root_object;
   g_root_object.name = "root";
@@ -53,7 +55,7 @@ void grpc_iomgr_init(void) {
   grpc_iomgr_platform_init();
 }
 
-void grpc_iomgr_start(void) { grpc_timer_manager_init(); }
+void grpc_iomgr_start(grpc_exec_ctx *exec_ctx) { grpc_timer_manager_init(); }
 
 static size_t count_objects(void) {
   grpc_iomgr_object *obj;
@@ -78,6 +80,7 @@ void grpc_iomgr_shutdown(grpc_exec_ctx *exec_ctx) {
 
   grpc_timer_manager_shutdown();
   grpc_iomgr_platform_flush();
+  grpc_executor_shutdown(exec_ctx);
 
   gpr_mu_lock(&g_mu);
   g_shutdown = 1;

src/core/lib/iomgr/iomgr.h

@@ -23,10 +23,10 @@
 #include "src/core/lib/iomgr/port.h"
 
 /** Initializes the iomgr. */
-void grpc_iomgr_init(void);
+void grpc_iomgr_init(grpc_exec_ctx *exec_ctx);
 
 /** Starts any background threads for iomgr. */
-void grpc_iomgr_start(void);
+void grpc_iomgr_start(grpc_exec_ctx *exec_ctx);
 
 /** Signals the intention to shutdown the iomgr. Expects to be able to flush
  * exec_ctx. */

src/core/lib/iomgr/resource_quota.c

@@ -566,7 +566,7 @@ static void rq_reclamation_done(grpc_exec_ctx *exec_ctx, void *rq,
 grpc_resource_quota *grpc_resource_quota_create(const char *name) {
   grpc_resource_quota *resource_quota = gpr_malloc(sizeof(*resource_quota));
   gpr_ref_init(&resource_quota->refs, 1);
-  resource_quota->combiner = grpc_combiner_create(NULL);
+  resource_quota->combiner = grpc_combiner_create();
   resource_quota->free_pool = INT64_MAX;
   resource_quota->size = INT64_MAX;
   gpr_atm_no_barrier_store(&resource_quota->last_size, GPR_ATM_MAX);
@@ -579,12 +579,11 @@ grpc_resource_quota *grpc_resource_quota_create(const char *name) {
     gpr_asprintf(&resource_quota->name, "anonymous_pool_%" PRIxPTR,
                  (intptr_t)resource_quota);
   }
-  grpc_closure_init(
-      &resource_quota->rq_step_closure, rq_step, resource_quota,
-      grpc_combiner_finally_scheduler(resource_quota->combiner, true));
+  grpc_closure_init(&resource_quota->rq_step_closure, rq_step, resource_quota,
+                    grpc_combiner_finally_scheduler(resource_quota->combiner));
   grpc_closure_init(&resource_quota->rq_reclamation_done_closure,
                     rq_reclamation_done, resource_quota,
-                    grpc_combiner_scheduler(resource_quota->combiner, false));
+                    grpc_combiner_scheduler(resource_quota->combiner));
   for (int i = 0; i < GRPC_RULIST_COUNT; i++) {
     resource_quota->roots[i] = NULL;
   }
@@ -689,18 +688,18 @@ grpc_resource_user *grpc_resource_user_create(
       grpc_resource_quota_ref_internal(resource_quota);
   grpc_closure_init(&resource_user->allocate_closure, &ru_allocate,
                     resource_user,
-                    grpc_combiner_scheduler(resource_quota->combiner, false));
+                    grpc_combiner_scheduler(resource_quota->combiner));
   grpc_closure_init(&resource_user->add_to_free_pool_closure,
                     &ru_add_to_free_pool, resource_user,
-                    grpc_combiner_scheduler(resource_quota->combiner, false));
+                    grpc_combiner_scheduler(resource_quota->combiner));
   grpc_closure_init(&resource_user->post_reclaimer_closure[0],
                     &ru_post_benign_reclaimer, resource_user,
-                    grpc_combiner_scheduler(resource_quota->combiner, false));
+                    grpc_combiner_scheduler(resource_quota->combiner));
   grpc_closure_init(&resource_user->post_reclaimer_closure[1],
                     &ru_post_destructive_reclaimer, resource_user,
-                    grpc_combiner_scheduler(resource_quota->combiner, false));
+                    grpc_combiner_scheduler(resource_quota->combiner));
   grpc_closure_init(&resource_user->destroy_closure, &ru_destroy, resource_user,
-                    grpc_combiner_scheduler(resource_quota->combiner, false));
+                    grpc_combiner_scheduler(resource_quota->combiner));
   gpr_mu_init(&resource_user->mu);
   gpr_atm_rel_store(&resource_user->refs, 1);
   gpr_atm_rel_store(&resource_user->shutdown, 0);
@@ -757,12 +756,12 @@ void grpc_resource_user_unref(grpc_exec_ctx *exec_ctx,
 void grpc_resource_user_shutdown(grpc_exec_ctx *exec_ctx,
                                  grpc_resource_user *resource_user) {
   if (gpr_atm_full_fetch_add(&resource_user->shutdown, 1) == 0) {
-    grpc_closure_sched(exec_ctx,
-                       grpc_closure_create(
-                           ru_shutdown, resource_user,
-                           grpc_combiner_scheduler(
-                               resource_user->resource_quota->combiner, false)),
-                       GRPC_ERROR_NONE);
+    grpc_closure_sched(
+        exec_ctx,
+        grpc_closure_create(
+            ru_shutdown, resource_user,
+            grpc_combiner_scheduler(resource_user->resource_quota->combiner)),
+        GRPC_ERROR_NONE);
   }
 }
 

src/core/lib/iomgr/tcp_posix.c

@@ -543,26 +543,15 @@ static int tcp_get_fd(grpc_endpoint *ep) {
   return tcp->fd;
 }
 
-static grpc_workqueue *tcp_get_workqueue(grpc_endpoint *ep) {
-  grpc_tcp *tcp = (grpc_tcp *)ep;
-  return grpc_fd_get_workqueue(tcp->em_fd);
-}
-
 static grpc_resource_user *tcp_get_resource_user(grpc_endpoint *ep) {
   grpc_tcp *tcp = (grpc_tcp *)ep;
   return tcp->resource_user;
 }
 
-static const grpc_endpoint_vtable vtable = {tcp_read,
-                                            tcp_write,
-                                            tcp_get_workqueue,
-                                            tcp_add_to_pollset,
-                                            tcp_add_to_pollset_set,
-                                            tcp_shutdown,
-                                            tcp_destroy,
-                                            tcp_get_resource_user,
-                                            tcp_get_peer,
-                                            tcp_get_fd};
+static const grpc_endpoint_vtable vtable = {
+    tcp_read,     tcp_write,   tcp_add_to_pollset,    tcp_add_to_pollset_set,
+    tcp_shutdown, tcp_destroy, tcp_get_resource_user, tcp_get_peer,
+    tcp_get_fd};
 
 #define MAX_CHUNK_SIZE 32 * 1024 * 1024
 

src/core/lib/iomgr/tcp_uv.c

@@ -318,15 +318,12 @@ static grpc_resource_user *uv_get_resource_user(grpc_endpoint *ep) {
   return tcp->resource_user;
 }
 
-static grpc_workqueue *uv_get_workqueue(grpc_endpoint *ep) { return NULL; }
-
 static int uv_get_fd(grpc_endpoint *ep) { return -1; }
 
 static grpc_endpoint_vtable vtable = {
-    uv_endpoint_read,  uv_endpoint_write,     uv_get_workqueue,
-    uv_add_to_pollset, uv_add_to_pollset_set, uv_endpoint_shutdown,
-    uv_destroy,        uv_get_resource_user,  uv_get_peer,
-    uv_get_fd};
+    uv_endpoint_read,      uv_endpoint_write,    uv_add_to_pollset,
+    uv_add_to_pollset_set, uv_endpoint_shutdown, uv_destroy,
+    uv_get_resource_user,  uv_get_peer,          uv_get_fd};
 
 grpc_endpoint *grpc_tcp_create(uv_tcp_t *handle,
                                grpc_resource_quota *resource_quota,

src/core/lib/iomgr/tcp_windows.c

@@ -395,8 +395,6 @@ static char *win_get_peer(grpc_endpoint *ep) {
   return gpr_strdup(tcp->peer_string);
 }
 
-static grpc_workqueue *win_get_workqueue(grpc_endpoint *ep) { return NULL; }
-
 static grpc_resource_user *win_get_resource_user(grpc_endpoint *ep) {
   grpc_tcp *tcp = (grpc_tcp *)ep;
   return tcp->resource_user;
@@ -404,16 +402,10 @@ static grpc_resource_user *win_get_resource_user(grpc_endpoint *ep) {
 
 static int win_get_fd(grpc_endpoint *ep) { return -1; }
 
-static grpc_endpoint_vtable vtable = {win_read,
-                                      win_write,
-                                      win_get_workqueue,
-                                      win_add_to_pollset,
-                                      win_add_to_pollset_set,
-                                      win_shutdown,
-                                      win_destroy,
-                                      win_get_resource_user,
-                                      win_get_peer,
-                                      win_get_fd};
+static grpc_endpoint_vtable vtable = {
+    win_read,     win_write,   win_add_to_pollset,    win_add_to_pollset_set,
+    win_shutdown, win_destroy, win_get_resource_user, win_get_peer,
+    win_get_fd};
 
 grpc_endpoint *grpc_tcp_create(grpc_exec_ctx *exec_ctx, grpc_winsocket *socket,
                                grpc_channel_args *channel_args,

src/core/lib/iomgr/workqueue.h

@@ -1,72 +0,0 @@
-/*
- *
- * Copyright 2015 gRPC authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-#ifndef GRPC_CORE_LIB_IOMGR_WORKQUEUE_H
-#define GRPC_CORE_LIB_IOMGR_WORKQUEUE_H
-
-#include "src/core/lib/iomgr/closure.h"
-#include "src/core/lib/iomgr/exec_ctx.h"
-#include "src/core/lib/iomgr/iomgr.h"
-#include "src/core/lib/iomgr/pollset.h"
-#include "src/core/lib/iomgr/pollset_set.h"
-#include "src/core/lib/iomgr/port.h"
-
-#ifdef GPR_WINDOWS
-#include "src/core/lib/iomgr/workqueue_windows.h"
-#endif
-
-/* grpc_workqueue is forward declared in exec_ctx.h */
-
-/* Reference counting functions. Use the macro's always
-   (GRPC_WORKQUEUE_{REF,UNREF}).
-
-   Pass in a descriptive reason string for reffing/unreffing as the last
-   argument to each macro. When GRPC_WORKQUEUE_REFCOUNT_DEBUG is defined, that
-   string will be printed alongside the refcount. When it is not defined, the
-   string will be discarded at compilation time. */
-
-/*#define GRPC_WORKQUEUE_REFCOUNT_DEBUG*/
-#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
-#define GRPC_WORKQUEUE_REF(p, r) \
-  grpc_workqueue_ref((p), __FILE__, __LINE__, (r))
-#define GRPC_WORKQUEUE_UNREF(exec_ctx, p, r) \
-  grpc_workqueue_unref((exec_ctx), (p), __FILE__, __LINE__, (r))
-grpc_workqueue *grpc_workqueue_ref(grpc_workqueue *workqueue, const char *file,
-                                   int line, const char *reason);
-void grpc_workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
-                          const char *file, int line, const char *reason);
-#else
-#define GRPC_WORKQUEUE_REF(p, r) grpc_workqueue_ref((p))
-#define GRPC_WORKQUEUE_UNREF(cl, p, r) grpc_workqueue_unref((cl), (p))
-grpc_workqueue *grpc_workqueue_ref(grpc_workqueue *workqueue);
-void grpc_workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue);
-#endif
-
-/** Fetch the workqueue closure scheduler. Items added to a work queue will be
-    started in approximately the order they were enqueued, on some thread that
-    may or may not be the current thread. Successive closures enqueued onto a
-    workqueue MAY be executed concurrently.
-
-    It is generally more expensive to add a closure to a workqueue than to the
-    execution context, both in terms of CPU work and in execution latency.
-
-    Use work queues when it's important that other threads be given a chance to
-    tackle some workload. */
-grpc_closure_scheduler *grpc_workqueue_scheduler(grpc_workqueue *workqueue);
-
-#endif /* GRPC_CORE_LIB_IOMGR_WORKQUEUE_H */

src/core/lib/iomgr/workqueue_uv.c

@@ -1,50 +0,0 @@
-/*
- *
- * Copyright 2016 gRPC authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-#include "src/core/lib/iomgr/port.h"
-
-#ifdef GRPC_UV
-
-#include "src/core/lib/iomgr/workqueue.h"
-
-// Minimal implementation of grpc_workqueue for libuv
-// Works by directly enqueuing workqueue items onto the current execution
-// context, which is at least correct, if not performant or in the spirit of
-// workqueues.
-
-void grpc_workqueue_flush(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue) {}
-
-#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
-grpc_workqueue *grpc_workqueue_ref(grpc_workqueue *workqueue, const char *file,
-                                   int line, const char *reason) {
-  return workqueue;
-}
-void grpc_workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
-                          const char *file, int line, const char *reason) {}
-#else
-grpc_workqueue *grpc_workqueue_ref(grpc_workqueue *workqueue) {
-  return workqueue;
-}
-void grpc_workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue) {}
-#endif
-
-grpc_closure_scheduler *grpc_workqueue_scheduler(grpc_workqueue *workqueue) {
-  return grpc_schedule_on_exec_ctx;
-}
-
-#endif /* GPR_UV */

src/core/lib/iomgr/workqueue_uv.h

@@ -1,22 +0,0 @@
-/*
- *
- * Copyright 2016 gRPC authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-#ifndef GRPC_CORE_LIB_IOMGR_WORKQUEUE_UV_H
-#define GRPC_CORE_LIB_IOMGR_WORKQUEUE_UV_H
-
-#endif /* GRPC_CORE_LIB_IOMGR_WORKQUEUE_UV_H */

src/core/lib/iomgr/workqueue_windows.c

@@ -1,48 +0,0 @@
-/*
- *
- * Copyright 2015 gRPC authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-#include <grpc/support/port_platform.h>
-
-#ifdef GPR_WINDOWS
-
-#include "src/core/lib/iomgr/workqueue.h"
-
-// Minimal implementation of grpc_workqueue for Windows
-// Works by directly enqueuing workqueue items onto the current execution
-// context, which is at least correct, if not performant or in the spirit of
-// workqueues.
-
-#ifdef GRPC_WORKQUEUE_REFCOUNT_DEBUG
-grpc_workqueue *grpc_workqueue_ref(grpc_workqueue *workqueue, const char *file,
-                                   int line, const char *reason) {
-  return workqueue;
-}
-void grpc_workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue,
-                          const char *file, int line, const char *reason) {}
-#else
-grpc_workqueue *grpc_workqueue_ref(grpc_workqueue *workqueue) {
-  return workqueue;
-}
-void grpc_workqueue_unref(grpc_exec_ctx *exec_ctx, grpc_workqueue *workqueue) {}
-#endif
-
-grpc_closure_scheduler *grpc_workqueue_scheduler(grpc_workqueue *workqueue) {
-  return grpc_schedule_on_exec_ctx;
-}
-
-#endif /* GPR_WINDOWS */

src/core/lib/iomgr/workqueue_windows.h

@@ -1,22 +0,0 @@
-/*
- *
- * Copyright 2015 gRPC authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-#ifndef GRPC_CORE_LIB_IOMGR_WORKQUEUE_WINDOWS_H
-#define GRPC_CORE_LIB_IOMGR_WORKQUEUE_WINDOWS_H
-
-#endif /* GRPC_CORE_LIB_IOMGR_WORKQUEUE_WINDOWS_H */

src/core/lib/security/transport/client_auth_filter.c

@@ -50,7 +50,8 @@ typedef struct {
   */
   grpc_polling_entity *pollent;
   grpc_transport_stream_op_batch op;
-  uint8_t security_context_set;
+  gpr_atm security_context_set;
+  gpr_mu security_context_mu;
   grpc_linked_mdelem md_links[MAX_CREDENTIALS_METADATA_COUNT];
   grpc_auth_metadata_context auth_md_context;
 } call_data;
@@ -238,19 +239,26 @@ static void auth_start_transport_op(grpc_exec_ctx *exec_ctx,
   grpc_linked_mdelem *l;
   grpc_client_security_context *sec_ctx = NULL;
 
-  if (!op->cancel_stream && calld->security_context_set == 0) {
-    calld->security_context_set = 1;
-    GPR_ASSERT(op->payload->context != NULL);
-    if (op->payload->context[GRPC_CONTEXT_SECURITY].value == NULL) {
-      op->payload->context[GRPC_CONTEXT_SECURITY].value =
-          grpc_client_security_context_create();
-      op->payload->context[GRPC_CONTEXT_SECURITY].destroy =
-          grpc_client_security_context_destroy;
+  if (!op->cancel_stream) {
+    /* double checked lock over security context to ensure it's set once */
+    if (gpr_atm_acq_load(&calld->security_context_set) == 0) {
+      gpr_mu_lock(&calld->security_context_mu);
+      if (gpr_atm_acq_load(&calld->security_context_set) == 0) {
+        GPR_ASSERT(op->payload->context != NULL);
+        if (op->payload->context[GRPC_CONTEXT_SECURITY].value == NULL) {
+          op->payload->context[GRPC_CONTEXT_SECURITY].value =
+              grpc_client_security_context_create();
+          op->payload->context[GRPC_CONTEXT_SECURITY].destroy =
+              grpc_client_security_context_destroy;
+        }
+        sec_ctx = op->payload->context[GRPC_CONTEXT_SECURITY].value;
+        GRPC_AUTH_CONTEXT_UNREF(sec_ctx->auth_context, "client auth filter");
+        sec_ctx->auth_context =
+            GRPC_AUTH_CONTEXT_REF(chand->auth_context, "client_auth_filter");
+        gpr_atm_rel_store(&calld->security_context_set, 1);
+      }
+      gpr_mu_unlock(&calld->security_context_mu);
     }
-    sec_ctx = op->payload->context[GRPC_CONTEXT_SECURITY].value;
-    GRPC_AUTH_CONTEXT_UNREF(sec_ctx->auth_context, "client auth filter");
-    sec_ctx->auth_context =
-        GRPC_AUTH_CONTEXT_REF(chand->auth_context, "client_auth_filter");
   }
 
   if (op->send_initial_metadata) {
@@ -297,6 +305,7 @@ static grpc_error *init_call_elem(grpc_exec_ctx *exec_ctx,
                                   const grpc_call_element_args *args) {
   call_data *calld = elem->call_data;
   memset(calld, 0, sizeof(*calld));
+  gpr_mu_init(&calld->security_context_mu);
   return GRPC_ERROR_NONE;
 }
 
@@ -320,6 +329,7 @@ static void destroy_call_elem(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
     grpc_slice_unref_internal(exec_ctx, calld->method);
   }
   reset_auth_metadata_context(&calld->auth_md_context);
+  gpr_mu_destroy(&calld->security_context_mu);
 }
 
 /* Constructor for channel_data */

src/core/lib/security/transport/secure_endpoint.c

@@ -365,11 +365,6 @@ static int endpoint_get_fd(grpc_endpoint *secure_ep) {
   return grpc_endpoint_get_fd(ep->wrapped_ep);
 }
 
-static grpc_workqueue *endpoint_get_workqueue(grpc_endpoint *secure_ep) {
-  secure_endpoint *ep = (secure_endpoint *)secure_ep;
-  return grpc_endpoint_get_workqueue(ep->wrapped_ep);
-}
-
 static grpc_resource_user *endpoint_get_resource_user(
     grpc_endpoint *secure_ep) {
   secure_endpoint *ep = (secure_endpoint *)secure_ep;
@@ -378,7 +373,6 @@ static grpc_resource_user *endpoint_get_resource_user(
 
 static const grpc_endpoint_vtable vtable = {endpoint_read,
                                             endpoint_write,
-                                            endpoint_get_workqueue,
                                             endpoint_add_to_pollset,
                                             endpoint_add_to_pollset_set,
                                             endpoint_shutdown,

src/core/lib/surface/call.c

@@ -1453,7 +1453,6 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
   grpc_transport_stream_op_batch *stream_op = &bctl->op;
   grpc_transport_stream_op_batch_payload *stream_op_payload =
       &call->stream_op_payload;
-  stream_op->covered_by_poller = true;
 
   /* rewrite batch ops into a transport op */
   for (i = 0; i < nops; i++) {
@@ -1642,10 +1641,6 @@ static grpc_call_error call_start_batch(grpc_exec_ctx *exec_ctx,
           error = GRPC_CALL_ERROR_TOO_MANY_OPERATIONS;
           goto done_with_error;
         }
-        /* IF this is a server, then GRPC_OP_RECV_INITIAL_METADATA *must* come
-           from server.c. In that case, it's coming from accept_stream, and in
-           that case we're not necessarily covered by a poller. */
-        stream_op->covered_by_poller = call->is_client;
         call->received_initial_metadata = true;
         call->buffered_metadata[0] =
             op->data.recv_initial_metadata.recv_initial_metadata;

src/core/lib/surface/init.c

@@ -113,6 +113,7 @@ void grpc_init(void) {
   int i;
   gpr_once_init(&g_basic_init, do_basic_init);
 
+  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   gpr_mu_lock(&g_init_mu);
   if (++g_initializations == 1) {
     gpr_time_init();
@@ -139,8 +140,7 @@ void grpc_init(void) {
     grpc_register_tracer("pending_tags", &grpc_trace_pending_tags);
 #endif
     grpc_security_pre_init();
-    grpc_iomgr_init();
-    grpc_executor_init();
+    grpc_iomgr_init(&exec_ctx);
     gpr_timers_global_init();
     grpc_handshaker_factory_registry_init();
     grpc_security_init();
@@ -156,19 +156,20 @@ void grpc_init(void) {
     grpc_tracer_init("GRPC_TRACE");
     /* no more changes to channel init pipelines */
     grpc_channel_init_finalize();
-    grpc_iomgr_start();
+    grpc_iomgr_start(&exec_ctx);
   }
   gpr_mu_unlock(&g_init_mu);
+  grpc_exec_ctx_finish(&exec_ctx);
   GRPC_API_TRACE("grpc_init(void)", 0, ());
 }
 
 void grpc_shutdown(void) {
   int i;
   GRPC_API_TRACE("grpc_shutdown(void)", 0, ());
-  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+  grpc_exec_ctx exec_ctx =
+      GRPC_EXEC_CTX_INITIALIZER(0, grpc_never_ready_to_finish, NULL);
   gpr_mu_lock(&g_init_mu);
   if (--g_initializations == 0) {
-    grpc_executor_shutdown(&exec_ctx);
     grpc_iomgr_shutdown(&exec_ctx);
     gpr_timers_global_destroy();
     grpc_tracer_shutdown();

src/core/lib/transport/transport.h

@@ -112,10 +112,6 @@ typedef struct grpc_transport_stream_op_batch {
   /** Values for the stream op (fields set are determined by flags above) */
   grpc_transport_stream_op_batch_payload *payload;
 
-  /** Is the completion of this op covered by a poller (if false: the op should
-      complete independently of some pollset being polled) */
-  bool covered_by_poller : 1;
-
   /** Send initial metadata to the peer, from the provided metadata batch. */
   bool send_initial_metadata : 1;
 

src/core/lib/transport/transport_op_string.c

@@ -64,9 +64,6 @@ char *grpc_transport_stream_op_batch_string(
   gpr_strvec b;
   gpr_strvec_init(&b);
 
-  gpr_strvec_add(
-      &b, gpr_strdup(op->covered_by_poller ? "[COVERED]" : "[UNCOVERED]"));
-
   if (op->send_initial_metadata) {
     gpr_strvec_add(&b, gpr_strdup(" "));
     gpr_strvec_add(&b, gpr_strdup("SEND_INITIAL_METADATA{"));

src/python/grpcio/grpc_core_dependencies.py

@@ -143,8 +143,6 @@ CORE_SOURCE_FILES = [
   'src/core/lib/iomgr/wakeup_fd_nospecial.c',
   'src/core/lib/iomgr/wakeup_fd_pipe.c',
   'src/core/lib/iomgr/wakeup_fd_posix.c',
-  'src/core/lib/iomgr/workqueue_uv.c',
-  'src/core/lib/iomgr/workqueue_windows.c',
   'src/core/lib/json/json.c',
   'src/core/lib/json/json_reader.c',
   'src/core/lib/json/json_string.c',

test/core/bad_client/bad_client.c

@@ -169,8 +169,13 @@ void grpc_run_bad_client_test(
       grpc_endpoint_read(&exec_ctx, sfd.client, &args.incoming,
                          &read_done_closure);
       grpc_exec_ctx_finish(&exec_ctx);
-      GPR_ASSERT(
-          gpr_event_wait(&args.read_done, grpc_timeout_seconds_to_deadline(5)));
+      gpr_timespec deadline = grpc_timeout_seconds_to_deadline(5);
+      while (!gpr_event_get(&args.read_done)) {
+        GPR_ASSERT(gpr_time_cmp(deadline, gpr_now(deadline.clock_type)) > 0);
+        GPR_ASSERT(grpc_completion_queue_next(
+                       a.cq, grpc_timeout_milliseconds_to_deadline(100), NULL)
+                       .type == GRPC_QUEUE_TIMEOUT);
+      }
       grpc_slice_buffer_destroy_internal(&exec_ctx, &args.incoming);
     }
     // Shutdown.

test/core/bad_client/tests/server_registered_method.c

@@ -68,27 +68,11 @@ static void verifier_succeeds(grpc_server *server, grpc_completion_queue *cq,
 
 static void verifier_fails(grpc_server *server, grpc_completion_queue *cq,
                            void *registered_method) {
-  grpc_call_error error;
-  grpc_call *s;
-  cq_verifier *cqv = cq_verifier_create(cq);
-  grpc_metadata_array request_metadata_recv;
-  gpr_timespec deadline;
-  grpc_byte_buffer *payload = NULL;
-
-  grpc_metadata_array_init(&request_metadata_recv);
-
-  error = grpc_server_request_registered_call(server, registered_method, &s,
-                                              &deadline, &request_metadata_recv,
-                                              &payload, cq, cq, tag(101));
-  GPR_ASSERT(GRPC_CALL_OK == error);
-  CQ_EXPECT_COMPLETION(cqv, tag(101), 1);
-  cq_verify(cqv);
-
-  GPR_ASSERT(payload == NULL);
-
-  grpc_metadata_array_destroy(&request_metadata_recv);
-  grpc_call_unref(s);
-  cq_verifier_destroy(cqv);
+  while (grpc_server_has_open_connections(server)) {
+    GPR_ASSERT(grpc_completion_queue_next(
+                   cq, grpc_timeout_milliseconds_to_deadline(20), NULL)
+                   .type == GRPC_QUEUE_TIMEOUT);
+  }
 }
 
 int main(int argc, char **argv) {

test/core/client_channel/resolvers/dns_resolver_connectivity_test.c

@@ -133,11 +133,10 @@ static void call_resolver_next_after_locking(grpc_exec_ctx *exec_ctx,
   a->resolver = resolver;
   a->result = result;
   a->on_complete = on_complete;
-  grpc_closure_sched(
-      exec_ctx,
-      grpc_closure_create(call_resolver_next_now_lock_taken, a,
-                          grpc_combiner_scheduler(resolver->combiner, false)),
-      GRPC_ERROR_NONE);
+  grpc_closure_sched(exec_ctx, grpc_closure_create(
+                                   call_resolver_next_now_lock_taken, a,
+                                   grpc_combiner_scheduler(resolver->combiner)),
+                     GRPC_ERROR_NONE);
 }
 
 int main(int argc, char **argv) {
@@ -145,7 +144,7 @@ int main(int argc, char **argv) {
 
   grpc_init();
   gpr_mu_init(&g_mu);
-  g_combiner = grpc_combiner_create(NULL);
+  g_combiner = grpc_combiner_create();
   grpc_resolve_address = my_resolve_address;
   grpc_dns_lookup_ares = my_dns_lookup_ares;
   grpc_channel_args *result = (grpc_channel_args *)1;

test/core/client_channel/resolvers/dns_resolver_test.c

@@ -67,7 +67,7 @@ int main(int argc, char **argv) {
   grpc_test_init(argc, argv);
   grpc_init();
 
-  g_combiner = grpc_combiner_create(NULL);
+  g_combiner = grpc_combiner_create();
 
   dns = grpc_resolver_factory_lookup("dns");
 

test/core/client_channel/resolvers/fake_resolver_test.c

@@ -52,12 +52,11 @@ static grpc_resolver *build_fake_resolver(
 typedef struct on_resolution_arg {
   grpc_channel_args *resolver_result;
   grpc_channel_args *expected_resolver_result;
-  bool was_called;
+  gpr_event ev;
 } on_resolution_arg;
 
 void on_resolution_cb(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {
   on_resolution_arg *res = arg;
-  res->was_called = true;
   // We only check the addresses channel arg because that's the only one
   // explicitly set by the test via
   // grpc_fake_resolver_response_generator_set_response.
@@ -69,11 +68,12 @@ void on_resolution_cb(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {
       grpc_lb_addresses_cmp(actual_lb_addresses, expected_lb_addresses) == 0);
   grpc_channel_args_destroy(exec_ctx, res->resolver_result);
   grpc_channel_args_destroy(exec_ctx, res->expected_resolver_result);
+  gpr_event_set(&res->ev, (void *)1);
 }
 
 static void test_fake_resolver() {
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-  grpc_combiner *combiner = grpc_combiner_create(NULL);
+  grpc_combiner *combiner = grpc_combiner_create();
   // Create resolver.
   grpc_fake_resolver_response_generator *response_generator =
       grpc_fake_resolver_response_generator_create();
@@ -100,8 +100,9 @@ static void test_fake_resolver() {
   on_resolution_arg on_res_arg;
   memset(&on_res_arg, 0, sizeof(on_res_arg));
   on_res_arg.expected_resolver_result = results;
+  gpr_event_init(&on_res_arg.ev);
   grpc_closure *on_resolution = grpc_closure_create(
-      on_resolution_cb, &on_res_arg, grpc_combiner_scheduler(combiner, false));
+      on_resolution_cb, &on_res_arg, grpc_combiner_scheduler(combiner));
 
   // Set resolver results and trigger first resolution. on_resolution_cb
   // performs the checks.
@@ -110,7 +111,8 @@ static void test_fake_resolver() {
   grpc_resolver_next_locked(&exec_ctx, resolver, &on_res_arg.resolver_result,
                             on_resolution);
   grpc_exec_ctx_flush(&exec_ctx);
-  GPR_ASSERT(on_res_arg.was_called);
+  GPR_ASSERT(gpr_event_wait(&on_res_arg.ev,
+                            grpc_timeout_seconds_to_deadline(5)) != NULL);
 
   // Setup update.
   grpc_uri *uris_update[] = {
@@ -135,8 +137,9 @@ static void test_fake_resolver() {
   on_resolution_arg on_res_arg_update;
   memset(&on_res_arg_update, 0, sizeof(on_res_arg_update));
   on_res_arg_update.expected_resolver_result = results_update;
+  gpr_event_init(&on_res_arg_update.ev);
   on_resolution = grpc_closure_create(on_resolution_cb, &on_res_arg_update,
-                                      grpc_combiner_scheduler(combiner, false));
+                                      grpc_combiner_scheduler(combiner));
 
   // Set updated resolver results and trigger a second resolution.
   grpc_fake_resolver_response_generator_set_response(
@@ -144,7 +147,8 @@ static void test_fake_resolver() {
   grpc_resolver_next_locked(&exec_ctx, resolver,
                             &on_res_arg_update.resolver_result, on_resolution);
   grpc_exec_ctx_flush(&exec_ctx);
-  GPR_ASSERT(on_res_arg.was_called);
+  GPR_ASSERT(gpr_event_wait(&on_res_arg_update.ev,
+                            grpc_timeout_seconds_to_deadline(5)) != NULL);
 
   // Requesting a new resolution without re-senting the response shouldn't
   // trigger the resolution callback.
@@ -152,7 +156,9 @@ static void test_fake_resolver() {
   grpc_resolver_next_locked(&exec_ctx, resolver, &on_res_arg.resolver_result,
                             on_resolution);
   grpc_exec_ctx_flush(&exec_ctx);
-  GPR_ASSERT(!on_res_arg.was_called);
+  GPR_ASSERT(gpr_event_wait(&on_res_arg.ev,
+                            grpc_timeout_milliseconds_to_deadline(100)) ==
+             NULL);
 
   GRPC_COMBINER_UNREF(&exec_ctx, combiner, "test_fake_resolver");
   GRPC_RESOLVER_UNREF(&exec_ctx, resolver, "test_fake_resolver");

test/core/client_channel/resolvers/sockaddr_resolver_test.c

@@ -89,7 +89,7 @@ int main(int argc, char **argv) {
   grpc_test_init(argc, argv);
   grpc_init();
 
-  g_combiner = grpc_combiner_create(NULL);
+  g_combiner = grpc_combiner_create();
 
   ipv4 = grpc_resolver_factory_lookup("ipv4");
   ipv6 = grpc_resolver_factory_lookup("ipv6");

test/core/end2end/fixtures/http_proxy_fixture.c

@@ -388,19 +388,19 @@ static void on_accept(grpc_exec_ctx* exec_ctx, void* arg,
   grpc_pollset_set_add_pollset(exec_ctx, conn->pollset_set, proxy->pollset);
   grpc_endpoint_add_to_pollset_set(exec_ctx, endpoint, conn->pollset_set);
   grpc_closure_init(&conn->on_read_request_done, on_read_request_done, conn,
-                    grpc_combiner_scheduler(conn->proxy->combiner, false));
+                    grpc_combiner_scheduler(conn->proxy->combiner));
   grpc_closure_init(&conn->on_server_connect_done, on_server_connect_done, conn,
-                    grpc_combiner_scheduler(conn->proxy->combiner, false));
+                    grpc_combiner_scheduler(conn->proxy->combiner));
   grpc_closure_init(&conn->on_write_response_done, on_write_response_done, conn,
-                    grpc_combiner_scheduler(conn->proxy->combiner, false));
+                    grpc_combiner_scheduler(conn->proxy->combiner));
   grpc_closure_init(&conn->on_client_read_done, on_client_read_done, conn,
-                    grpc_combiner_scheduler(conn->proxy->combiner, false));
+                    grpc_combiner_scheduler(conn->proxy->combiner));
   grpc_closure_init(&conn->on_client_write_done, on_client_write_done, conn,
-                    grpc_combiner_scheduler(conn->proxy->combiner, false));
+                    grpc_combiner_scheduler(conn->proxy->combiner));
   grpc_closure_init(&conn->on_server_read_done, on_server_read_done, conn,
-                    grpc_combiner_scheduler(conn->proxy->combiner, false));
+                    grpc_combiner_scheduler(conn->proxy->combiner));
   grpc_closure_init(&conn->on_server_write_done, on_server_write_done, conn,
-                    grpc_combiner_scheduler(conn->proxy->combiner, false));
+                    grpc_combiner_scheduler(conn->proxy->combiner));
   grpc_slice_buffer_init(&conn->client_read_buffer);
   grpc_slice_buffer_init(&conn->client_deferred_write_buffer);
   grpc_slice_buffer_init(&conn->client_write_buffer);
@@ -441,7 +441,7 @@ grpc_end2end_http_proxy* grpc_end2end_http_proxy_create(void) {
   grpc_end2end_http_proxy* proxy =
       (grpc_end2end_http_proxy*)gpr_malloc(sizeof(*proxy));
   memset(proxy, 0, sizeof(*proxy));
-  proxy->combiner = grpc_combiner_create(NULL);
+  proxy->combiner = grpc_combiner_create();
   gpr_ref_init(&proxy->users, 1);
   // Construct proxy address.
   const int proxy_port = grpc_pick_unused_port_or_die();

test/core/end2end/fuzzers/api_fuzzer.c

@@ -28,6 +28,7 @@
 #include "src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_wrapper.h"
 #include "src/core/ext/transport/chttp2/transport/chttp2_transport.h"
 #include "src/core/lib/channel/channel_args.h"
+#include "src/core/lib/iomgr/executor.h"
 #include "src/core/lib/iomgr/resolve_address.h"
 #include "src/core/lib/iomgr/tcp_client.h"
 #include "src/core/lib/iomgr/timer.h"
@@ -736,6 +737,11 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
   gpr_now_impl = now_impl;
   grpc_init();
   grpc_timer_manager_set_threading(false);
+  {
+    grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+    grpc_executor_set_threading(&exec_ctx, false);
+    grpc_exec_ctx_finish(&exec_ctx);
+  }
   grpc_resolve_address = my_resolve_address;
   grpc_dns_lookup_ares = my_dns_lookup_ares;
 

test/core/end2end/fuzzers/client_fuzzer.c

@@ -22,6 +22,7 @@
 #include <grpc/support/alloc.h>
 
 #include "src/core/ext/transport/chttp2/transport/chttp2_transport.h"
+#include "src/core/lib/iomgr/executor.h"
 #include "src/core/lib/slice/slice_internal.h"
 #include "src/core/lib/surface/channel.h"
 #include "test/core/util/memory_counters.h"
@@ -43,6 +44,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
   if (leak_check) grpc_memory_counters_init();
   grpc_init();
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+  grpc_executor_set_threading(&exec_ctx, false);
 
   grpc_resource_quota *resource_quota =
       grpc_resource_quota_create("client_fuzzer");

test/core/end2end/fuzzers/server_fuzzer.c

@@ -19,6 +19,7 @@
 #include <grpc/grpc.h>
 
 #include "src/core/ext/transport/chttp2/transport/chttp2_transport.h"
+#include "src/core/lib/iomgr/executor.h"
 #include "src/core/lib/slice/slice_internal.h"
 #include "src/core/lib/surface/server.h"
 #include "test/core/util/memory_counters.h"
@@ -41,6 +42,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
   if (leak_check) grpc_memory_counters_init();
   grpc_init();
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+  grpc_executor_set_threading(&exec_ctx, false);
 
   grpc_resource_quota *resource_quota =
       grpc_resource_quota_create("server_fuzzer");

test/core/iomgr/combiner_test.c

@@ -29,27 +29,29 @@
 static void test_no_op(void) {
   gpr_log(GPR_DEBUG, "test_no_op");
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-  GRPC_COMBINER_UNREF(&exec_ctx, grpc_combiner_create(NULL), "test_no_op");
+  GRPC_COMBINER_UNREF(&exec_ctx, grpc_combiner_create(), "test_no_op");
   grpc_exec_ctx_finish(&exec_ctx);
 }
 
-static void set_bool_to_true(grpc_exec_ctx *exec_ctx, void *value,
-                             grpc_error *error) {
-  *(bool *)value = true;
+static void set_event_to_true(grpc_exec_ctx *exec_ctx, void *value,
+                              grpc_error *error) {
+  gpr_event_set(value, (void *)1);
 }
 
 static void test_execute_one(void) {
   gpr_log(GPR_DEBUG, "test_execute_one");
 
-  grpc_combiner *lock = grpc_combiner_create(NULL);
-  bool done = false;
+  grpc_combiner *lock = grpc_combiner_create();
+  gpr_event done;
+  gpr_event_init(&done);
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   grpc_closure_sched(&exec_ctx,
-                     grpc_closure_create(set_bool_to_true, &done,
-                                         grpc_combiner_scheduler(lock, false)),
+                     grpc_closure_create(set_event_to_true, &done,
+                                         grpc_combiner_scheduler(lock)),
                      GRPC_ERROR_NONE);
   grpc_exec_ctx_flush(&exec_ctx);
-  GPR_ASSERT(done);
+  GPR_ASSERT(gpr_event_wait(&done, grpc_timeout_seconds_to_deadline(5)) !=
+             NULL);
   GRPC_COMBINER_UNREF(&exec_ctx, lock, "test_execute_one");
   grpc_exec_ctx_finish(&exec_ctx);
 }
@@ -57,6 +59,7 @@ static void test_execute_one(void) {
 typedef struct {
   size_t ctr;
   grpc_combiner *lock;
+  gpr_event done;
 } thd_args;
 
 typedef struct {
@@ -80,23 +83,27 @@ static void execute_many_loop(void *a) {
       ex_args *c = gpr_malloc(sizeof(*c));
       c->ctr = &args->ctr;
       c->value = n++;
-      grpc_closure_sched(
-          &exec_ctx, grpc_closure_create(check_one, c, grpc_combiner_scheduler(
-                                                           args->lock, false)),
-          GRPC_ERROR_NONE);
+      grpc_closure_sched(&exec_ctx,
+                         grpc_closure_create(
+                             check_one, c, grpc_combiner_scheduler(args->lock)),
+                         GRPC_ERROR_NONE);
       grpc_exec_ctx_flush(&exec_ctx);
     }
     // sleep for a little bit, to test a combiner draining and another thread
     // picking it up
     gpr_sleep_until(grpc_timeout_milliseconds_to_deadline(100));
   }
+  grpc_closure_sched(&exec_ctx,
+                     grpc_closure_create(set_event_to_true, &args->done,
+                                         grpc_combiner_scheduler(args->lock)),
+                     GRPC_ERROR_NONE);
   grpc_exec_ctx_finish(&exec_ctx);
 }
 
 static void test_execute_many(void) {
   gpr_log(GPR_DEBUG, "test_execute_many");
 
-  grpc_combiner *lock = grpc_combiner_create(NULL);
+  grpc_combiner *lock = grpc_combiner_create();
   gpr_thd_id thds[100];
   thd_args ta[GPR_ARRAY_SIZE(thds)];
   for (size_t i = 0; i < GPR_ARRAY_SIZE(thds); i++) {
@@ -104,9 +111,12 @@ static void test_execute_many(void) {
     gpr_thd_options_set_joinable(&options);
     ta[i].ctr = 0;
     ta[i].lock = lock;
+    gpr_event_init(&ta[i].done);
     GPR_ASSERT(gpr_thd_new(&thds[i], execute_many_loop, &ta[i], &options));
   }
   for (size_t i = 0; i < GPR_ARRAY_SIZE(thds); i++) {
+    GPR_ASSERT(gpr_event_wait(&ta[i].done,
+                              gpr_inf_future(GPR_CLOCK_REALTIME)) != NULL);
     gpr_thd_join(thds[i]);
   }
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
@@ -114,30 +124,32 @@ static void test_execute_many(void) {
   grpc_exec_ctx_finish(&exec_ctx);
 }
 
-static bool got_in_finally = false;
+static gpr_event got_in_finally;
 
 static void in_finally(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {
-  got_in_finally = true;
+  gpr_event_set(&got_in_finally, (void *)1);
 }
 
 static void add_finally(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {
-  grpc_closure_sched(exec_ctx, grpc_closure_create(
-                                   in_finally, NULL,
-                                   grpc_combiner_finally_scheduler(arg, false)),
+  grpc_closure_sched(exec_ctx,
+                     grpc_closure_create(in_finally, arg,
+                                         grpc_combiner_finally_scheduler(arg)),
                      GRPC_ERROR_NONE);
 }
 
 static void test_execute_finally(void) {
   gpr_log(GPR_DEBUG, "test_execute_finally");
 
-  grpc_combiner *lock = grpc_combiner_create(NULL);
+  grpc_combiner *lock = grpc_combiner_create();
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-  grpc_closure_sched(&exec_ctx,
-                     grpc_closure_create(add_finally, lock,
-                                         grpc_combiner_scheduler(lock, false)),
-                     GRPC_ERROR_NONE);
+  gpr_event_init(&got_in_finally);
+  grpc_closure_sched(
+      &exec_ctx,
+      grpc_closure_create(add_finally, lock, grpc_combiner_scheduler(lock)),
+      GRPC_ERROR_NONE);
   grpc_exec_ctx_flush(&exec_ctx);
-  GPR_ASSERT(got_in_finally);
+  GPR_ASSERT(gpr_event_wait(&got_in_finally,
+                            grpc_timeout_seconds_to_deadline(5)) != NULL);
   GRPC_COMBINER_UNREF(&exec_ctx, lock, "test_execute_finally");
   grpc_exec_ctx_finish(&exec_ctx);
 }

test/core/iomgr/endpoint_tests.c

@@ -250,25 +250,30 @@ static void read_and_write_test(grpc_endpoint_test_config config,
 
 static void inc_on_failure(grpc_exec_ctx *exec_ctx, void *arg,
                            grpc_error *error) {
+  gpr_mu_lock(g_mu);
   *(int *)arg += (error != GRPC_ERROR_NONE);
+  GPR_ASSERT(GRPC_LOG_IF_ERROR("kick", grpc_pollset_kick(g_pollset, NULL)));
+  gpr_mu_unlock(g_mu);
 }
 
 static void wait_for_fail_count(grpc_exec_ctx *exec_ctx, int *fail_count,
                                 int want_fail_count) {
   grpc_exec_ctx_flush(exec_ctx);
-  for (int i = 0; i < 5 && *fail_count < want_fail_count; i++) {
+  gpr_mu_lock(g_mu);
+  gpr_timespec deadline = grpc_timeout_seconds_to_deadline(10);
+  while (gpr_time_cmp(gpr_now(deadline.clock_type), deadline) < 0 &&
+         *fail_count < want_fail_count) {
     grpc_pollset_worker *worker = NULL;
-    gpr_timespec now = gpr_now(GPR_CLOCK_REALTIME);
-    gpr_timespec deadline =
-        gpr_time_add(now, gpr_time_from_seconds(1, GPR_TIMESPAN));
-    gpr_mu_lock(g_mu);
     GPR_ASSERT(GRPC_LOG_IF_ERROR(
         "pollset_work",
-        grpc_pollset_work(exec_ctx, g_pollset, &worker, now, deadline)));
+        grpc_pollset_work(exec_ctx, g_pollset, &worker,
+                          gpr_now(deadline.clock_type), deadline)));
     gpr_mu_unlock(g_mu);
     grpc_exec_ctx_flush(exec_ctx);
+    gpr_mu_lock(g_mu);
   }
   GPR_ASSERT(*fail_count == want_fail_count);
+  gpr_mu_unlock(g_mu);
 }
 
 static void multiple_shutdown_test(grpc_endpoint_test_config config) {

test/core/iomgr/ev_epollsig_linux_test.c

@@ -32,7 +32,6 @@
 #include <grpc/support/useful.h>
 
 #include "src/core/lib/iomgr/iomgr.h"
-#include "src/core/lib/iomgr/workqueue.h"
 #include "test/core/util/test_config.h"
 
 typedef struct test_pollset {
@@ -116,86 +115,6 @@ static void test_pollset_cleanup(grpc_exec_ctx *exec_ctx,
   }
 }
 
-static void increment(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {
-  ++*(int *)arg;
-}
-
-/*
- * Validate that merging two workqueues preserves the closures in each queue.
- * This is a regression test for a bug in
- * polling_island_merge()[ev_epoll_linux.c], where the parent relationship was
- * inverted.
- */
-
-#define NUM_FDS 2
-#define NUM_POLLSETS 2
-#define NUM_CLOSURES 4
-
-static void test_pollset_queue_merge_items() {
-  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-  test_fd tfds[NUM_FDS];
-  int fds[NUM_FDS];
-  test_pollset pollsets[NUM_POLLSETS];
-  grpc_closure closures[NUM_CLOSURES];
-  int i;
-  int result = 0;
-
-  test_fd_init(tfds, fds, NUM_FDS);
-  test_pollset_init(pollsets, NUM_POLLSETS);
-
-  /* Two distinct polling islands, each with their own FD and pollset. */
-  for (i = 0; i < NUM_FDS; i++) {
-    grpc_pollset_add_fd(&exec_ctx, pollsets[i].pollset, tfds[i].fd);
-    grpc_exec_ctx_flush(&exec_ctx);
-  }
-
-  /* Enqeue the closures, 3 to polling island 0 and 1 to polling island 1. */
-  grpc_closure_init(
-      closures, increment, &result,
-      grpc_workqueue_scheduler(grpc_fd_get_polling_island(tfds[0].fd)));
-  grpc_closure_init(
-      closures + 1, increment, &result,
-      grpc_workqueue_scheduler(grpc_fd_get_polling_island(tfds[0].fd)));
-  grpc_closure_init(
-      closures + 2, increment, &result,
-      grpc_workqueue_scheduler(grpc_fd_get_polling_island(tfds[0].fd)));
-  grpc_closure_init(
-      closures + 3, increment, &result,
-      grpc_workqueue_scheduler(grpc_fd_get_polling_island(tfds[1].fd)));
-  for (i = 0; i < NUM_CLOSURES; ++i) {
-    grpc_closure_sched(&exec_ctx, closures + i, GRPC_ERROR_NONE);
-  }
-
-  /* Merge the two polling islands. */
-  grpc_pollset_add_fd(&exec_ctx, pollsets[0].pollset, tfds[1].fd);
-  grpc_exec_ctx_flush(&exec_ctx);
-
-  /*
-   * Execute the closures, verify we see each one execute when executing work on
-   * the merged polling island.
-   */
-  grpc_pollset_worker *worker = NULL;
-  for (i = 0; i < NUM_CLOSURES; ++i) {
-    const gpr_timespec deadline = gpr_time_add(
-        gpr_now(GPR_CLOCK_MONOTONIC), gpr_time_from_seconds(2, GPR_TIMESPAN));
-    gpr_mu_lock(pollsets[1].mu);
-    GRPC_LOG_IF_ERROR(
-        "grpc_pollset_work",
-        grpc_pollset_work(&exec_ctx, pollsets[1].pollset, &worker,
-                          gpr_now(GPR_CLOCK_MONOTONIC), deadline));
-    gpr_mu_unlock(pollsets[1].mu);
-  }
-  GPR_ASSERT(result == NUM_CLOSURES);
-
-  test_fd_cleanup(&exec_ctx, tfds, NUM_FDS);
-  test_pollset_cleanup(&exec_ctx, pollsets, NUM_POLLSETS);
-  grpc_exec_ctx_finish(&exec_ctx);
-}
-
-#undef NUM_FDS
-#undef NUM_POLLSETS
-#undef NUM_CLOSURES
-
 /*
  * Cases to test:
  *  case 1) Polling islands of both fd and pollset are NULL
@@ -387,13 +306,13 @@ static void test_threading(void) {
 int main(int argc, char **argv) {
   const char *poll_strategy = NULL;
   grpc_test_init(argc, argv);
-  grpc_iomgr_init();
-  grpc_iomgr_start();
+  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+  grpc_iomgr_init(&exec_ctx);
+  grpc_iomgr_start(&exec_ctx);
 
   poll_strategy = grpc_get_poll_strategy_name();
   if (poll_strategy != NULL && strcmp(poll_strategy, "epollsig") == 0) {
     test_add_fd_to_pollset();
-    test_pollset_queue_merge_items();
     test_threading();
   } else {
     gpr_log(GPR_INFO,
@@ -402,11 +321,8 @@ int main(int argc, char **argv) {
             poll_strategy);
   }
 
-  {
-    grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-    grpc_iomgr_shutdown(&exec_ctx);
-    grpc_exec_ctx_finish(&exec_ctx);
-  }
+  grpc_iomgr_shutdown(&exec_ctx);
+  grpc_exec_ctx_finish(&exec_ctx);
   return 0;
 }
 #else /* defined(GRPC_LINUX_EPOLL) */

test/core/iomgr/fd_conservation_posix_test.c

@@ -30,8 +30,9 @@ int main(int argc, char **argv) {
   grpc_endpoint_pair p;
 
   grpc_test_init(argc, argv);
-  grpc_iomgr_init();
-  grpc_iomgr_start();
+  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+  grpc_iomgr_init(&exec_ctx);
+  grpc_iomgr_start(&exec_ctx);
 
   /* set max # of file descriptors to a low value, and
      verify we can create and destroy many more than this number
@@ -42,19 +43,15 @@ int main(int argc, char **argv) {
       grpc_resource_quota_create("fd_conservation_posix_test");
 
   for (i = 0; i < 100; i++) {
-    grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
     p = grpc_iomgr_create_endpoint_pair("test", NULL);
     grpc_endpoint_destroy(&exec_ctx, p.client);
     grpc_endpoint_destroy(&exec_ctx, p.server);
-    grpc_exec_ctx_finish(&exec_ctx);
+    grpc_exec_ctx_flush(&exec_ctx);
   }
 
   grpc_resource_quota_unref(resource_quota);
 
-  {
-    grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-    grpc_iomgr_shutdown(&exec_ctx);
-    grpc_exec_ctx_finish(&exec_ctx);
-  }
+  grpc_iomgr_shutdown(&exec_ctx);
+  grpc_exec_ctx_finish(&exec_ctx);
   return 0;
 }

test/core/iomgr/fd_posix_test.c

@@ -527,8 +527,8 @@ int main(int argc, char **argv) {
   grpc_closure destroyed;
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   grpc_test_init(argc, argv);
-  grpc_iomgr_init();
-  grpc_iomgr_start();
+  grpc_iomgr_init(&exec_ctx);
+  grpc_iomgr_start(&exec_ctx);
   g_pollset = gpr_zalloc(grpc_pollset_size());
   grpc_pollset_init(g_pollset, &g_mu);
   test_grpc_fd();

test/core/iomgr/pollset_set_test.c

@@ -432,8 +432,8 @@ int main(int argc, char **argv) {
   const char *poll_strategy = grpc_get_poll_strategy_name();
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   grpc_test_init(argc, argv);
-  grpc_iomgr_init();
-  grpc_iomgr_start();
+  grpc_iomgr_init(&exec_ctx);
+  grpc_iomgr_start(&exec_ctx);
 
   if (poll_strategy != NULL &&
       (strcmp(poll_strategy, "epoll") == 0 ||

test/core/iomgr/resolve_address_posix_test.c

@@ -159,16 +159,13 @@ static void test_unix_socket_path_name_too_long(void) {
 
 int main(int argc, char **argv) {
   grpc_test_init(argc, argv);
-  grpc_executor_init();
-  grpc_iomgr_init();
-  grpc_iomgr_start();
+  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+  grpc_iomgr_init(&exec_ctx);
+  grpc_iomgr_start(&exec_ctx);
   test_unix_socket();
   test_unix_socket_path_name_too_long();
-  {
-    grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-    grpc_executor_shutdown(&exec_ctx);
-    grpc_iomgr_shutdown(&exec_ctx);
-    grpc_exec_ctx_finish(&exec_ctx);
-  }
+  grpc_executor_shutdown(&exec_ctx);
+  grpc_iomgr_shutdown(&exec_ctx);
+  grpc_exec_ctx_finish(&exec_ctx);
   return 0;
 }

test/core/iomgr/resolve_address_test.c

@@ -58,7 +58,9 @@ void args_finish(grpc_exec_ctx *exec_ctx, args_struct *args) {
   grpc_closure do_nothing_cb;
   grpc_closure_init(&do_nothing_cb, do_nothing, NULL,
                     grpc_schedule_on_exec_ctx);
+  gpr_mu_lock(args->mu);
   grpc_pollset_shutdown(exec_ctx, args->pollset, &do_nothing_cb);
+  gpr_mu_unlock(args->mu);
   // exec_ctx needs to be flushed before calling grpc_pollset_destroy()
   grpc_exec_ctx_flush(exec_ctx);
   grpc_pollset_destroy(exec_ctx, args->pollset);
@@ -248,9 +250,9 @@ static void test_unparseable_hostports(void) {
 
 int main(int argc, char **argv) {
   grpc_test_init(argc, argv);
-  grpc_executor_init();
-  grpc_iomgr_init();
-  grpc_iomgr_start();
+  grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
+  grpc_iomgr_init(&exec_ctx);
+  grpc_iomgr_start(&exec_ctx);
   test_localhost();
   test_default_port();
   test_non_numeric_default_port();
@@ -259,11 +261,8 @@ int main(int argc, char **argv) {
   test_ipv6_without_port();
   test_invalid_ip_addresses();
   test_unparseable_hostports();
-  {
-    grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-    grpc_executor_shutdown(&exec_ctx);
-    grpc_iomgr_shutdown(&exec_ctx);
-    grpc_exec_ctx_finish(&exec_ctx);
-  }
+  grpc_executor_shutdown(&exec_ctx);
+  grpc_iomgr_shutdown(&exec_ctx);
+  grpc_exec_ctx_finish(&exec_ctx);
   return 0;
 }

test/core/iomgr/resource_quota_test.c

@@ -24,15 +24,30 @@
 #include "src/core/lib/slice/slice_internal.h"
 #include "test/core/util/test_config.h"
 
+gpr_mu g_mu;
+gpr_cv g_cv;
+
 static void inc_int_cb(grpc_exec_ctx *exec_ctx, void *a, grpc_error *error) {
+  gpr_mu_lock(&g_mu);
   ++*(int *)a;
+  gpr_cv_signal(&g_cv);
+  gpr_mu_unlock(&g_mu);
+}
+
+static void assert_counter_becomes(int *ctr, int value) {
+  gpr_mu_lock(&g_mu);
+  gpr_timespec deadline = grpc_timeout_seconds_to_deadline(5);
+  while (*ctr != value) {
+    GPR_ASSERT(!gpr_cv_wait(&g_cv, &g_mu, deadline));
+  }
+  gpr_mu_unlock(&g_mu);
 }
 
-static void set_bool_cb(grpc_exec_ctx *exec_ctx, void *a, grpc_error *error) {
-  *(bool *)a = true;
+static void set_event_cb(grpc_exec_ctx *exec_ctx, void *a, grpc_error *error) {
+  gpr_event_set((gpr_event *)a, (void *)1);
 }
-grpc_closure *set_bool(bool *p) {
-  return grpc_closure_create(set_bool_cb, p, grpc_schedule_on_exec_ctx);
+grpc_closure *set_event(gpr_event *ev) {
+  return grpc_closure_create(set_event_cb, ev, grpc_schedule_on_exec_ctx);
 }
 
 typedef struct {
@@ -139,11 +154,13 @@ static void test_simple_async_alloc(void) {
   grpc_resource_quota_resize(q, 1024 * 1024);
   grpc_resource_user *usr = grpc_resource_user_create(q, "usr");
   {
-    bool done = false;
+    gpr_event ev;
+    gpr_event_init(&ev);
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-    grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_bool(&done));
+    grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_event(&ev));
     grpc_exec_ctx_finish(&exec_ctx);
-    GPR_ASSERT(done);
+    GPR_ASSERT(gpr_event_wait(&ev, grpc_timeout_seconds_to_deadline(5)) !=
+               NULL);
   }
   {
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
@@ -160,15 +177,18 @@ static void test_async_alloc_blocked_by_size(void) {
       grpc_resource_quota_create("test_async_alloc_blocked_by_size");
   grpc_resource_quota_resize(q, 1);
   grpc_resource_user *usr = grpc_resource_user_create(q, "usr");
-  bool done = false;
+  gpr_event ev;
+  gpr_event_init(&ev);
   {
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-    grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_bool(&done));
+    grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_event(&ev));
     grpc_exec_ctx_finish(&exec_ctx);
-    GPR_ASSERT(!done);
+    GPR_ASSERT(gpr_event_wait(
+                   &ev, grpc_timeout_milliseconds_to_deadline(100)) == NULL);
   }
   grpc_resource_quota_resize(q, 1024);
-  GPR_ASSERT(done);
+  GPR_ASSERT(gpr_event_wait(&ev, grpc_timeout_seconds_to_deadline(5)) != NULL);
+  ;
   {
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
     grpc_resource_user_free(&exec_ctx, usr, 1024);
@@ -185,11 +205,14 @@ static void test_scavenge(void) {
   grpc_resource_user *usr1 = grpc_resource_user_create(q, "usr1");
   grpc_resource_user *usr2 = grpc_resource_user_create(q, "usr2");
   {
-    bool done = false;
+    gpr_event ev;
+    gpr_event_init(&ev);
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-    grpc_resource_user_alloc(&exec_ctx, usr1, 1024, set_bool(&done));
+    grpc_resource_user_alloc(&exec_ctx, usr1, 1024, set_event(&ev));
     grpc_exec_ctx_finish(&exec_ctx);
-    GPR_ASSERT(done);
+    GPR_ASSERT(gpr_event_wait(&ev, grpc_timeout_seconds_to_deadline(5)) !=
+               NULL);
+    ;
   }
   {
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
@@ -197,11 +220,14 @@ static void test_scavenge(void) {
     grpc_exec_ctx_finish(&exec_ctx);
   }
   {
-    bool done = false;
+    gpr_event ev;
+    gpr_event_init(&ev);
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-    grpc_resource_user_alloc(&exec_ctx, usr2, 1024, set_bool(&done));
+    grpc_resource_user_alloc(&exec_ctx, usr2, 1024, set_event(&ev));
     grpc_exec_ctx_finish(&exec_ctx);
-    GPR_ASSERT(done);
+    GPR_ASSERT(gpr_event_wait(&ev, grpc_timeout_seconds_to_deadline(5)) !=
+               NULL);
+    ;
   }
   {
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
@@ -219,26 +245,31 @@ static void test_scavenge_blocked(void) {
   grpc_resource_quota_resize(q, 1024);
   grpc_resource_user *usr1 = grpc_resource_user_create(q, "usr1");
   grpc_resource_user *usr2 = grpc_resource_user_create(q, "usr2");
-  bool done;
+  gpr_event ev;
   {
-    done = false;
+    gpr_event_init(&ev);
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-    grpc_resource_user_alloc(&exec_ctx, usr1, 1024, set_bool(&done));
+    grpc_resource_user_alloc(&exec_ctx, usr1, 1024, set_event(&ev));
     grpc_exec_ctx_finish(&exec_ctx);
-    GPR_ASSERT(done);
+    GPR_ASSERT(gpr_event_wait(&ev, grpc_timeout_seconds_to_deadline(5)) !=
+               NULL);
+    ;
   }
   {
-    done = false;
+    gpr_event_init(&ev);
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-    grpc_resource_user_alloc(&exec_ctx, usr2, 1024, set_bool(&done));
+    grpc_resource_user_alloc(&exec_ctx, usr2, 1024, set_event(&ev));
     grpc_exec_ctx_finish(&exec_ctx);
-    GPR_ASSERT(!done);
+    GPR_ASSERT(gpr_event_wait(
+                   &ev, grpc_timeout_milliseconds_to_deadline(100)) == NULL);
   }
   {
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
     grpc_resource_user_free(&exec_ctx, usr1, 1024);
     grpc_exec_ctx_finish(&exec_ctx);
-    GPR_ASSERT(done);
+    GPR_ASSERT(gpr_event_wait(&ev, grpc_timeout_seconds_to_deadline(5)) !=
+               NULL);
+    ;
   }
   {
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
@@ -257,27 +288,35 @@ static void test_blocked_until_scheduled_reclaim(void) {
   grpc_resource_quota_resize(q, 1024);
   grpc_resource_user *usr = grpc_resource_user_create(q, "usr");
   {
-    bool done = false;
+    gpr_event ev;
+    gpr_event_init(&ev);
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-    grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_bool(&done));
+    grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_event(&ev));
     grpc_exec_ctx_finish(&exec_ctx);
-    GPR_ASSERT(done);
+    GPR_ASSERT(gpr_event_wait(&ev, grpc_timeout_seconds_to_deadline(5)) !=
+               NULL);
+    ;
   }
-  bool reclaim_done = false;
+  gpr_event reclaim_done;
+  gpr_event_init(&reclaim_done);
   {
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
     grpc_resource_user_post_reclaimer(
         &exec_ctx, usr, false,
-        make_reclaimer(usr, 1024, set_bool(&reclaim_done)));
+        make_reclaimer(usr, 1024, set_event(&reclaim_done)));
     grpc_exec_ctx_finish(&exec_ctx);
   }
   {
-    bool done = false;
+    gpr_event ev;
+    gpr_event_init(&ev);
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-    grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_bool(&done));
+    grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_event(&ev));
     grpc_exec_ctx_finish(&exec_ctx);
-    GPR_ASSERT(reclaim_done);
-    GPR_ASSERT(done);
+    GPR_ASSERT(gpr_event_wait(&reclaim_done,
+                              grpc_timeout_seconds_to_deadline(5)) != NULL);
+    GPR_ASSERT(gpr_event_wait(&ev, grpc_timeout_seconds_to_deadline(5)) !=
+               NULL);
+    ;
   }
   {
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
@@ -296,27 +335,35 @@ static void test_blocked_until_scheduled_reclaim_and_scavenge(void) {
   grpc_resource_user *usr1 = grpc_resource_user_create(q, "usr1");
   grpc_resource_user *usr2 = grpc_resource_user_create(q, "usr2");
   {
-    bool done = false;
+    gpr_event ev;
+    gpr_event_init(&ev);
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-    grpc_resource_user_alloc(&exec_ctx, usr1, 1024, set_bool(&done));
+    grpc_resource_user_alloc(&exec_ctx, usr1, 1024, set_event(&ev));
     grpc_exec_ctx_finish(&exec_ctx);
-    GPR_ASSERT(done);
+    GPR_ASSERT(gpr_event_wait(&ev, grpc_timeout_seconds_to_deadline(5)) !=
+               NULL);
+    ;
   }
-  bool reclaim_done = false;
+  gpr_event reclaim_done;
+  gpr_event_init(&reclaim_done);
   {
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
     grpc_resource_user_post_reclaimer(
         &exec_ctx, usr1, false,
-        make_reclaimer(usr1, 1024, set_bool(&reclaim_done)));
+        make_reclaimer(usr1, 1024, set_event(&reclaim_done)));
     grpc_exec_ctx_finish(&exec_ctx);
   }
   {
-    bool done = false;
+    gpr_event ev;
+    gpr_event_init(&ev);
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-    grpc_resource_user_alloc(&exec_ctx, usr2, 1024, set_bool(&done));
+    grpc_resource_user_alloc(&exec_ctx, usr2, 1024, set_event(&ev));
     grpc_exec_ctx_finish(&exec_ctx);
-    GPR_ASSERT(reclaim_done);
-    GPR_ASSERT(done);
+    GPR_ASSERT(gpr_event_wait(&reclaim_done,
+                              grpc_timeout_seconds_to_deadline(5)) != NULL);
+    GPR_ASSERT(gpr_event_wait(&ev, grpc_timeout_seconds_to_deadline(5)) !=
+               NULL);
+    ;
   }
   {
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
@@ -335,27 +382,35 @@ static void test_blocked_until_scheduled_destructive_reclaim(void) {
   grpc_resource_quota_resize(q, 1024);
   grpc_resource_user *usr = grpc_resource_user_create(q, "usr");
   {
-    bool done = false;
+    gpr_event ev;
+    gpr_event_init(&ev);
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-    grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_bool(&done));
+    grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_event(&ev));
     grpc_exec_ctx_finish(&exec_ctx);
-    GPR_ASSERT(done);
+    GPR_ASSERT(gpr_event_wait(&ev, grpc_timeout_seconds_to_deadline(5)) !=
+               NULL);
+    ;
   }
-  bool reclaim_done = false;
+  gpr_event reclaim_done;
+  gpr_event_init(&reclaim_done);
   {
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
     grpc_resource_user_post_reclaimer(
         &exec_ctx, usr, true,
-        make_reclaimer(usr, 1024, set_bool(&reclaim_done)));
+        make_reclaimer(usr, 1024, set_event(&reclaim_done)));
     grpc_exec_ctx_finish(&exec_ctx);
   }
   {
-    bool done = false;
+    gpr_event ev;
+    gpr_event_init(&ev);
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-    grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_bool(&done));
+    grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_event(&ev));
     grpc_exec_ctx_finish(&exec_ctx);
-    GPR_ASSERT(reclaim_done);
-    GPR_ASSERT(done);
+    GPR_ASSERT(gpr_event_wait(&reclaim_done,
+                              grpc_timeout_seconds_to_deadline(5)) != NULL);
+    GPR_ASSERT(gpr_event_wait(&ev, grpc_timeout_seconds_to_deadline(5)) !=
+               NULL);
+    ;
   }
   {
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
@@ -372,23 +427,31 @@ static void test_unused_reclaim_is_cancelled(void) {
       grpc_resource_quota_create("test_unused_reclaim_is_cancelled");
   grpc_resource_quota_resize(q, 1024);
   grpc_resource_user *usr = grpc_resource_user_create(q, "usr");
-  bool benign_done = false;
-  bool destructive_done = false;
+  gpr_event benign_done;
+  gpr_event_init(&benign_done);
+  gpr_event destructive_done;
+  gpr_event_init(&destructive_done);
   {
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
     grpc_resource_user_post_reclaimer(
-        &exec_ctx, usr, false, make_unused_reclaimer(set_bool(&benign_done)));
+        &exec_ctx, usr, false, make_unused_reclaimer(set_event(&benign_done)));
     grpc_resource_user_post_reclaimer(
         &exec_ctx, usr, true,
-        make_unused_reclaimer(set_bool(&destructive_done)));
+        make_unused_reclaimer(set_event(&destructive_done)));
     grpc_exec_ctx_finish(&exec_ctx);
-    GPR_ASSERT(!benign_done);
-    GPR_ASSERT(!destructive_done);
+    GPR_ASSERT(gpr_event_wait(&benign_done,
+                              grpc_timeout_milliseconds_to_deadline(100)) ==
+               NULL);
+    GPR_ASSERT(gpr_event_wait(&destructive_done,
+                              grpc_timeout_milliseconds_to_deadline(100)) ==
+               NULL);
   }
   grpc_resource_quota_unref(q);
   destroy_user(usr);
-  GPR_ASSERT(benign_done);
-  GPR_ASSERT(destructive_done);
+  GPR_ASSERT(gpr_event_wait(&benign_done,
+                            grpc_timeout_seconds_to_deadline(5)) != NULL);
+  GPR_ASSERT(gpr_event_wait(&destructive_done,
+                            grpc_timeout_seconds_to_deadline(5)) != NULL);
 }
 
 static void test_benign_reclaim_is_preferred(void) {
@@ -397,35 +460,49 @@ static void test_benign_reclaim_is_preferred(void) {
       grpc_resource_quota_create("test_benign_reclaim_is_preferred");
   grpc_resource_quota_resize(q, 1024);
   grpc_resource_user *usr = grpc_resource_user_create(q, "usr");
-  bool benign_done = false;
-  bool destructive_done = false;
+  gpr_event benign_done;
+  gpr_event_init(&benign_done);
+  gpr_event destructive_done;
+  gpr_event_init(&destructive_done);
   {
-    bool done = false;
+    gpr_event ev;
+    gpr_event_init(&ev);
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-    grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_bool(&done));
+    grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_event(&ev));
     grpc_exec_ctx_finish(&exec_ctx);
-    GPR_ASSERT(done);
+    GPR_ASSERT(gpr_event_wait(&ev, grpc_timeout_seconds_to_deadline(5)) !=
+               NULL);
+    ;
   }
   {
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
     grpc_resource_user_post_reclaimer(
         &exec_ctx, usr, false,
-        make_reclaimer(usr, 1024, set_bool(&benign_done)));
+        make_reclaimer(usr, 1024, set_event(&benign_done)));
     grpc_resource_user_post_reclaimer(
         &exec_ctx, usr, true,
-        make_unused_reclaimer(set_bool(&destructive_done)));
+        make_unused_reclaimer(set_event(&destructive_done)));
     grpc_exec_ctx_finish(&exec_ctx);
-    GPR_ASSERT(!benign_done);
-    GPR_ASSERT(!destructive_done);
+    GPR_ASSERT(gpr_event_wait(&benign_done,
+                              grpc_timeout_milliseconds_to_deadline(100)) ==
+               NULL);
+    GPR_ASSERT(gpr_event_wait(&destructive_done,
+                              grpc_timeout_milliseconds_to_deadline(100)) ==
+               NULL);
   }
   {
-    bool done = false;
+    gpr_event ev;
+    gpr_event_init(&ev);
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-    grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_bool(&done));
+    grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_event(&ev));
     grpc_exec_ctx_finish(&exec_ctx);
-    GPR_ASSERT(benign_done);
-    GPR_ASSERT(!destructive_done);
-    GPR_ASSERT(done);
+    GPR_ASSERT(gpr_event_wait(&benign_done,
+                              grpc_timeout_seconds_to_deadline(5)) != NULL);
+    GPR_ASSERT(gpr_event_wait(&destructive_done,
+                              grpc_timeout_milliseconds_to_deadline(100)) ==
+               NULL);
+    GPR_ASSERT(gpr_event_wait(&ev, grpc_timeout_seconds_to_deadline(5)) !=
+               NULL);
   }
   {
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
@@ -434,8 +511,10 @@ static void test_benign_reclaim_is_preferred(void) {
   }
   grpc_resource_quota_unref(q);
   destroy_user(usr);
-  GPR_ASSERT(benign_done);
-  GPR_ASSERT(destructive_done);
+  GPR_ASSERT(gpr_event_wait(&benign_done,
+                            grpc_timeout_seconds_to_deadline(5)) != NULL);
+  GPR_ASSERT(gpr_event_wait(&destructive_done,
+                            grpc_timeout_seconds_to_deadline(5)) != NULL);
 }
 
 static void test_multiple_reclaims_can_be_triggered(void) {
@@ -444,35 +523,49 @@ static void test_multiple_reclaims_can_be_triggered(void) {
       grpc_resource_quota_create("test_multiple_reclaims_can_be_triggered");
   grpc_resource_quota_resize(q, 1024);
   grpc_resource_user *usr = grpc_resource_user_create(q, "usr");
-  bool benign_done = false;
-  bool destructive_done = false;
+  gpr_event benign_done;
+  gpr_event_init(&benign_done);
+  gpr_event destructive_done;
+  gpr_event_init(&destructive_done);
   {
-    bool done = false;
+    gpr_event ev;
+    gpr_event_init(&ev);
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-    grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_bool(&done));
+    grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_event(&ev));
     grpc_exec_ctx_finish(&exec_ctx);
-    GPR_ASSERT(done);
+    GPR_ASSERT(gpr_event_wait(&ev, grpc_timeout_seconds_to_deadline(5)) !=
+               NULL);
+    ;
   }
   {
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
     grpc_resource_user_post_reclaimer(
         &exec_ctx, usr, false,
-        make_reclaimer(usr, 512, set_bool(&benign_done)));
+        make_reclaimer(usr, 512, set_event(&benign_done)));
     grpc_resource_user_post_reclaimer(
         &exec_ctx, usr, true,
-        make_reclaimer(usr, 512, set_bool(&destructive_done)));
+        make_reclaimer(usr, 512, set_event(&destructive_done)));
     grpc_exec_ctx_finish(&exec_ctx);
-    GPR_ASSERT(!benign_done);
-    GPR_ASSERT(!destructive_done);
+    GPR_ASSERT(gpr_event_wait(&benign_done,
+                              grpc_timeout_milliseconds_to_deadline(100)) ==
+               NULL);
+    GPR_ASSERT(gpr_event_wait(&destructive_done,
+                              grpc_timeout_milliseconds_to_deadline(100)) ==
+               NULL);
   }
   {
-    bool done = false;
+    gpr_event ev;
+    gpr_event_init(&ev);
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-    grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_bool(&done));
+    grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_event(&ev));
     grpc_exec_ctx_finish(&exec_ctx);
-    GPR_ASSERT(benign_done);
-    GPR_ASSERT(destructive_done);
-    GPR_ASSERT(done);
+    GPR_ASSERT(gpr_event_wait(&benign_done,
+                              grpc_timeout_seconds_to_deadline(5)) != NULL);
+    GPR_ASSERT(gpr_event_wait(&destructive_done,
+                              grpc_timeout_seconds_to_deadline(5)) != NULL);
+    GPR_ASSERT(gpr_event_wait(&ev, grpc_timeout_seconds_to_deadline(5)) !=
+               NULL);
+    ;
   }
   {
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
@@ -481,8 +574,10 @@ static void test_multiple_reclaims_can_be_triggered(void) {
   }
   grpc_resource_quota_unref(q);
   destroy_user(usr);
-  GPR_ASSERT(benign_done);
-  GPR_ASSERT(destructive_done);
+  GPR_ASSERT(gpr_event_wait(&benign_done,
+                            grpc_timeout_seconds_to_deadline(5)) != NULL);
+  GPR_ASSERT(gpr_event_wait(&destructive_done,
+                            grpc_timeout_seconds_to_deadline(5)) != NULL);
 }
 
 static void test_resource_user_stays_allocated_until_memory_released(void) {
@@ -523,34 +618,44 @@ test_resource_user_stays_allocated_and_reclaimers_unrun_until_memory_released(
   grpc_resource_quota_resize(q, 1024);
   for (int i = 0; i < 10; i++) {
     grpc_resource_user *usr = grpc_resource_user_create(q, "usr");
-    bool reclaimer_cancelled = false;
+    gpr_event reclaimer_cancelled;
+    gpr_event_init(&reclaimer_cancelled);
     {
       grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
       grpc_resource_user_post_reclaimer(
           &exec_ctx, usr, false,
-          make_unused_reclaimer(set_bool(&reclaimer_cancelled)));
+          make_unused_reclaimer(set_event(&reclaimer_cancelled)));
       grpc_exec_ctx_finish(&exec_ctx);
-      GPR_ASSERT(!reclaimer_cancelled);
+      GPR_ASSERT(gpr_event_wait(&reclaimer_cancelled,
+                                grpc_timeout_milliseconds_to_deadline(100)) ==
+                 NULL);
     }
     {
-      bool allocated = false;
+      gpr_event allocated;
+      gpr_event_init(&allocated);
       grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-      grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_bool(&allocated));
+      grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_event(&allocated));
       grpc_exec_ctx_finish(&exec_ctx);
-      GPR_ASSERT(allocated);
-      GPR_ASSERT(!reclaimer_cancelled);
+      GPR_ASSERT(gpr_event_wait(&allocated,
+                                grpc_timeout_seconds_to_deadline(5)) != NULL);
+      GPR_ASSERT(gpr_event_wait(&reclaimer_cancelled,
+                                grpc_timeout_milliseconds_to_deadline(100)) ==
+                 NULL);
     }
     {
       grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
       grpc_resource_user_unref(&exec_ctx, usr);
       grpc_exec_ctx_finish(&exec_ctx);
-      GPR_ASSERT(!reclaimer_cancelled);
+      GPR_ASSERT(gpr_event_wait(&reclaimer_cancelled,
+                                grpc_timeout_milliseconds_to_deadline(100)) ==
+                 NULL);
     }
     {
       grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
       grpc_resource_user_free(&exec_ctx, usr, 1024);
       grpc_exec_ctx_finish(&exec_ctx);
-      GPR_ASSERT(reclaimer_cancelled);
+      GPR_ASSERT(gpr_event_wait(&reclaimer_cancelled,
+                                grpc_timeout_seconds_to_deadline(5)) != NULL);
     }
   }
   grpc_resource_quota_unref(q);
@@ -563,29 +668,37 @@ static void test_reclaimers_can_be_posted_repeatedly(void) {
   grpc_resource_quota_resize(q, 1024);
   grpc_resource_user *usr = grpc_resource_user_create(q, "usr");
   {
-    bool allocated = false;
+    gpr_event allocated;
+    gpr_event_init(&allocated);
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-    grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_bool(&allocated));
+    grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_event(&allocated));
     grpc_exec_ctx_finish(&exec_ctx);
-    GPR_ASSERT(allocated);
+    GPR_ASSERT(gpr_event_wait(&allocated,
+                              grpc_timeout_seconds_to_deadline(5)) != NULL);
   }
   for (int i = 0; i < 10; i++) {
-    bool reclaimer_done = false;
+    gpr_event reclaimer_done;
+    gpr_event_init(&reclaimer_done);
     {
       grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
       grpc_resource_user_post_reclaimer(
           &exec_ctx, usr, false,
-          make_reclaimer(usr, 1024, set_bool(&reclaimer_done)));
+          make_reclaimer(usr, 1024, set_event(&reclaimer_done)));
       grpc_exec_ctx_finish(&exec_ctx);
-      GPR_ASSERT(!reclaimer_done);
+      GPR_ASSERT(gpr_event_wait(&reclaimer_done,
+                                grpc_timeout_milliseconds_to_deadline(100)) ==
+                 NULL);
     }
     {
-      bool allocated = false;
+      gpr_event allocated;
+      gpr_event_init(&allocated);
       grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-      grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_bool(&allocated));
+      grpc_resource_user_alloc(&exec_ctx, usr, 1024, set_event(&allocated));
       grpc_exec_ctx_finish(&exec_ctx);
-      GPR_ASSERT(allocated);
-      GPR_ASSERT(reclaimer_done);
+      GPR_ASSERT(gpr_event_wait(&allocated,
+                                grpc_timeout_seconds_to_deadline(5)) != NULL);
+      GPR_ASSERT(gpr_event_wait(&reclaimer_done,
+                                grpc_timeout_seconds_to_deadline(5)) != NULL);
     }
   }
   {
@@ -617,7 +730,7 @@ static void test_one_slice(void) {
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
     grpc_resource_user_alloc_slices(&exec_ctx, &alloc, 1024, 1, &buffer);
     grpc_exec_ctx_finish(&exec_ctx);
-    GPR_ASSERT(num_allocs == start_allocs + 1);
+    assert_counter_becomes(&num_allocs, start_allocs + 1);
   }
 
   {
@@ -650,7 +763,7 @@ static void test_one_slice_deleted_late(void) {
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
     grpc_resource_user_alloc_slices(&exec_ctx, &alloc, 1024, 1, &buffer);
     grpc_exec_ctx_finish(&exec_ctx);
-    GPR_ASSERT(num_allocs == start_allocs + 1);
+    assert_counter_becomes(&num_allocs, start_allocs + 1);
   }
 
   {
@@ -694,7 +807,7 @@ static void test_negative_rq_free_pool(void) {
     grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
     grpc_resource_user_alloc_slices(&exec_ctx, &alloc, 1024, 1, &buffer);
     grpc_exec_ctx_finish(&exec_ctx);
-    GPR_ASSERT(num_allocs == start_allocs + 1);
+    assert_counter_becomes(&num_allocs, start_allocs + 1);
   }
 
   grpc_resource_quota_resize(q, 512);
@@ -720,6 +833,8 @@ static void test_negative_rq_free_pool(void) {
 int main(int argc, char **argv) {
   grpc_test_init(argc, argv);
   grpc_init();
+  gpr_mu_init(&g_mu);
+  gpr_cv_init(&g_cv);
   test_no_op();
   test_resize_then_destroy();
   test_resource_user_no_op();
@@ -742,6 +857,8 @@ int main(int argc, char **argv) {
   test_one_slice_deleted_late();
   test_resize_to_zero();
   test_negative_rq_free_pool();
+  gpr_mu_destroy(&g_mu);
+  gpr_cv_destroy(&g_cv);
   grpc_shutdown();
   return 0;
 }

test/core/iomgr/tcp_posix_test.c

@@ -147,6 +147,7 @@ static void read_cb(grpc_exec_ctx *exec_ctx, void *user_data,
   gpr_log(GPR_INFO, "Read %" PRIuPTR " bytes of %" PRIuPTR, read_bytes,
           state->target_read_bytes);
   if (state->read_bytes >= state->target_read_bytes) {
+    GPR_ASSERT(GRPC_LOG_IF_ERROR("kick", grpc_pollset_kick(g_pollset, NULL)));
     gpr_mu_unlock(g_mu);
   } else {
     grpc_endpoint_read(exec_ctx, state->ep, &state->incoming, &state->read_cb);

test/core/util/mock_endpoint.c

@@ -102,18 +102,9 @@ static grpc_resource_user *me_get_resource_user(grpc_endpoint *ep) {
 
 static int me_get_fd(grpc_endpoint *ep) { return -1; }
 
-static grpc_workqueue *me_get_workqueue(grpc_endpoint *ep) { return NULL; }
-
 static const grpc_endpoint_vtable vtable = {
-    me_read,
-    me_write,
-    me_get_workqueue,
-    me_add_to_pollset,
-    me_add_to_pollset_set,
-    me_shutdown,
-    me_destroy,
-    me_get_resource_user,
-    me_get_peer,
+    me_read,     me_write,   me_add_to_pollset,    me_add_to_pollset_set,
+    me_shutdown, me_destroy, me_get_resource_user, me_get_peer,
     me_get_fd,
 };
 

test/core/util/passthru_endpoint.c

@@ -154,23 +154,14 @@ static char *me_get_peer(grpc_endpoint *ep) {
 
 static int me_get_fd(grpc_endpoint *ep) { return -1; }
 
-static grpc_workqueue *me_get_workqueue(grpc_endpoint *ep) { return NULL; }
-
 static grpc_resource_user *me_get_resource_user(grpc_endpoint *ep) {
   half *m = (half *)ep;
   return m->resource_user;
 }
 
 static const grpc_endpoint_vtable vtable = {
-    me_read,
-    me_write,
-    me_get_workqueue,
-    me_add_to_pollset,
-    me_add_to_pollset_set,
-    me_shutdown,
-    me_destroy,
-    me_get_resource_user,
-    me_get_peer,
+    me_read,     me_write,   me_add_to_pollset,    me_add_to_pollset_set,
+    me_shutdown, me_destroy, me_get_resource_user, me_get_peer,
     me_get_fd,
 };
 

test/core/util/trickle_endpoint.c

@@ -77,11 +77,6 @@ static void te_write(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
   gpr_mu_unlock(&te->mu);
 }
 
-static grpc_workqueue *te_get_workqueue(grpc_endpoint *ep) {
-  trickle_endpoint *te = (trickle_endpoint *)ep;
-  return grpc_endpoint_get_workqueue(te->wrapped);
-}
-
 static void te_add_to_pollset(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
                               grpc_pollset *pollset) {
   trickle_endpoint *te = (trickle_endpoint *)ep;
@@ -140,16 +135,10 @@ static void te_finish_write(grpc_exec_ctx *exec_ctx, void *arg,
   gpr_mu_unlock(&te->mu);
 }
 
-static const grpc_endpoint_vtable vtable = {te_read,
-                                            te_write,
-                                            te_get_workqueue,
-                                            te_add_to_pollset,
-                                            te_add_to_pollset_set,
-                                            te_shutdown,
-                                            te_destroy,
-                                            te_get_resource_user,
-                                            te_get_peer,
-                                            te_get_fd};
+static const grpc_endpoint_vtable vtable = {
+    te_read,     te_write,   te_add_to_pollset,    te_add_to_pollset_set,
+    te_shutdown, te_destroy, te_get_resource_user, te_get_peer,
+    te_get_fd};
 
 grpc_endpoint *grpc_trickle_endpoint_create(grpc_endpoint *wrap,
                                             double bytes_per_second) {

test/cpp/microbenchmarks/bm_chttp2_transport.cc

@@ -45,16 +45,10 @@ auto &force_library_initialization = Library::get();
 class DummyEndpoint : public grpc_endpoint {
  public:
   DummyEndpoint() {
-    static const grpc_endpoint_vtable my_vtable = {read,
-                                                   write,
-                                                   get_workqueue,
-                                                   add_to_pollset,
-                                                   add_to_pollset_set,
-                                                   shutdown,
-                                                   destroy,
-                                                   get_resource_user,
-                                                   get_peer,
-                                                   get_fd};
+    static const grpc_endpoint_vtable my_vtable = {
+        read,     write,   add_to_pollset,    add_to_pollset_set,
+        shutdown, destroy, get_resource_user, get_peer,
+        get_fd};
     grpc_endpoint::vtable = &my_vtable;
     ru_ = grpc_resource_user_create(Library::get().rq(), "dummy_endpoint");
   }

test/cpp/microbenchmarks/bm_closure.cc

@@ -69,12 +69,12 @@ BENCHMARK(BM_ClosureInitAgainstExecCtx);
 
 static void BM_ClosureInitAgainstCombiner(benchmark::State& state) {
   TrackCounters track_counters;
-  grpc_combiner* combiner = grpc_combiner_create(NULL);
+  grpc_combiner* combiner = grpc_combiner_create();
   grpc_closure c;
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   while (state.KeepRunning()) {
     benchmark::DoNotOptimize(grpc_closure_init(
-        &c, DoNothing, NULL, grpc_combiner_scheduler(combiner, false)));
+        &c, DoNothing, NULL, grpc_combiner_scheduler(combiner)));
   }
   GRPC_COMBINER_UNREF(&exec_ctx, combiner, "finished");
   grpc_exec_ctx_finish(&exec_ctx);
@@ -244,10 +244,9 @@ BENCHMARK(BM_TryAcquireSpinlock);
 
 static void BM_ClosureSchedOnCombiner(benchmark::State& state) {
   TrackCounters track_counters;
-  grpc_combiner* combiner = grpc_combiner_create(NULL);
+  grpc_combiner* combiner = grpc_combiner_create();
   grpc_closure c;
-  grpc_closure_init(&c, DoNothing, NULL,
-                    grpc_combiner_scheduler(combiner, false));
+  grpc_closure_init(&c, DoNothing, NULL, grpc_combiner_scheduler(combiner));
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   while (state.KeepRunning()) {
     grpc_closure_sched(&exec_ctx, &c, GRPC_ERROR_NONE);
@@ -261,13 +260,11 @@ BENCHMARK(BM_ClosureSchedOnCombiner);
 
 static void BM_ClosureSched2OnCombiner(benchmark::State& state) {
   TrackCounters track_counters;
-  grpc_combiner* combiner = grpc_combiner_create(NULL);
+  grpc_combiner* combiner = grpc_combiner_create();
   grpc_closure c1;
   grpc_closure c2;
-  grpc_closure_init(&c1, DoNothing, NULL,
-                    grpc_combiner_scheduler(combiner, false));
-  grpc_closure_init(&c2, DoNothing, NULL,
-                    grpc_combiner_scheduler(combiner, false));
+  grpc_closure_init(&c1, DoNothing, NULL, grpc_combiner_scheduler(combiner));
+  grpc_closure_init(&c2, DoNothing, NULL, grpc_combiner_scheduler(combiner));
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   while (state.KeepRunning()) {
     grpc_closure_sched(&exec_ctx, &c1, GRPC_ERROR_NONE);
@@ -282,16 +279,13 @@ BENCHMARK(BM_ClosureSched2OnCombiner);
 
 static void BM_ClosureSched3OnCombiner(benchmark::State& state) {
   TrackCounters track_counters;
-  grpc_combiner* combiner = grpc_combiner_create(NULL);
+  grpc_combiner* combiner = grpc_combiner_create();
   grpc_closure c1;
   grpc_closure c2;
   grpc_closure c3;
-  grpc_closure_init(&c1, DoNothing, NULL,
-                    grpc_combiner_scheduler(combiner, false));
-  grpc_closure_init(&c2, DoNothing, NULL,
-                    grpc_combiner_scheduler(combiner, false));
-  grpc_closure_init(&c3, DoNothing, NULL,
-                    grpc_combiner_scheduler(combiner, false));
+  grpc_closure_init(&c1, DoNothing, NULL, grpc_combiner_scheduler(combiner));
+  grpc_closure_init(&c2, DoNothing, NULL, grpc_combiner_scheduler(combiner));
+  grpc_closure_init(&c3, DoNothing, NULL, grpc_combiner_scheduler(combiner));
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   while (state.KeepRunning()) {
     grpc_closure_sched(&exec_ctx, &c1, GRPC_ERROR_NONE);
@@ -307,14 +301,12 @@ BENCHMARK(BM_ClosureSched3OnCombiner);
 
 static void BM_ClosureSched2OnTwoCombiners(benchmark::State& state) {
   TrackCounters track_counters;
-  grpc_combiner* combiner1 = grpc_combiner_create(NULL);
-  grpc_combiner* combiner2 = grpc_combiner_create(NULL);
+  grpc_combiner* combiner1 = grpc_combiner_create();
+  grpc_combiner* combiner2 = grpc_combiner_create();
   grpc_closure c1;
   grpc_closure c2;
-  grpc_closure_init(&c1, DoNothing, NULL,
-                    grpc_combiner_scheduler(combiner1, false));
-  grpc_closure_init(&c2, DoNothing, NULL,
-                    grpc_combiner_scheduler(combiner2, false));
+  grpc_closure_init(&c1, DoNothing, NULL, grpc_combiner_scheduler(combiner1));
+  grpc_closure_init(&c2, DoNothing, NULL, grpc_combiner_scheduler(combiner2));
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   while (state.KeepRunning()) {
     grpc_closure_sched(&exec_ctx, &c1, GRPC_ERROR_NONE);
@@ -330,20 +322,16 @@ BENCHMARK(BM_ClosureSched2OnTwoCombiners);
 
 static void BM_ClosureSched4OnTwoCombiners(benchmark::State& state) {
   TrackCounters track_counters;
-  grpc_combiner* combiner1 = grpc_combiner_create(NULL);
-  grpc_combiner* combiner2 = grpc_combiner_create(NULL);
+  grpc_combiner* combiner1 = grpc_combiner_create();
+  grpc_combiner* combiner2 = grpc_combiner_create();
   grpc_closure c1;
   grpc_closure c2;
   grpc_closure c3;
   grpc_closure c4;
-  grpc_closure_init(&c1, DoNothing, NULL,
-                    grpc_combiner_scheduler(combiner1, false));
-  grpc_closure_init(&c2, DoNothing, NULL,
-                    grpc_combiner_scheduler(combiner2, false));
-  grpc_closure_init(&c3, DoNothing, NULL,
-                    grpc_combiner_scheduler(combiner1, false));
-  grpc_closure_init(&c4, DoNothing, NULL,
-                    grpc_combiner_scheduler(combiner2, false));
+  grpc_closure_init(&c1, DoNothing, NULL, grpc_combiner_scheduler(combiner1));
+  grpc_closure_init(&c2, DoNothing, NULL, grpc_combiner_scheduler(combiner2));
+  grpc_closure_init(&c3, DoNothing, NULL, grpc_combiner_scheduler(combiner1));
+  grpc_closure_init(&c4, DoNothing, NULL, grpc_combiner_scheduler(combiner2));
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
   while (state.KeepRunning()) {
     grpc_closure_sched(&exec_ctx, &c1, GRPC_ERROR_NONE);
@@ -403,8 +391,8 @@ BENCHMARK(BM_ClosureReschedOnExecCtx);
 static void BM_ClosureReschedOnCombiner(benchmark::State& state) {
   TrackCounters track_counters;
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-  grpc_combiner* combiner = grpc_combiner_create(NULL);
-  Rescheduler r(state, grpc_combiner_scheduler(combiner, false));
+  grpc_combiner* combiner = grpc_combiner_create();
+  Rescheduler r(state, grpc_combiner_scheduler(combiner));
   r.ScheduleFirst(&exec_ctx);
   grpc_exec_ctx_flush(&exec_ctx);
   GRPC_COMBINER_UNREF(&exec_ctx, combiner, "finished");
@@ -416,10 +404,10 @@ BENCHMARK(BM_ClosureReschedOnCombiner);
 static void BM_ClosureReschedOnCombinerFinally(benchmark::State& state) {
   TrackCounters track_counters;
   grpc_exec_ctx exec_ctx = GRPC_EXEC_CTX_INIT;
-  grpc_combiner* combiner = grpc_combiner_create(NULL);
-  Rescheduler r(state, grpc_combiner_finally_scheduler(combiner, false));
-  r.ScheduleFirstAgainstDifferentScheduler(
-      &exec_ctx, grpc_combiner_scheduler(combiner, false));
+  grpc_combiner* combiner = grpc_combiner_create();
+  Rescheduler r(state, grpc_combiner_finally_scheduler(combiner));
+  r.ScheduleFirstAgainstDifferentScheduler(&exec_ctx,
+                                           grpc_combiner_scheduler(combiner));
   grpc_exec_ctx_flush(&exec_ctx);
   GRPC_COMBINER_UNREF(&exec_ctx, combiner, "finished");
   grpc_exec_ctx_finish(&exec_ctx);

tools/doxygen/Doxyfile.core.internal

@@ -1207,11 +1207,6 @@ src/core/lib/iomgr/wakeup_fd_pipe.c \
 src/core/lib/iomgr/wakeup_fd_pipe.h \
 src/core/lib/iomgr/wakeup_fd_posix.c \
 src/core/lib/iomgr/wakeup_fd_posix.h \
-src/core/lib/iomgr/workqueue.h \
-src/core/lib/iomgr/workqueue_uv.c \
-src/core/lib/iomgr/workqueue_uv.h \
-src/core/lib/iomgr/workqueue_windows.c \
-src/core/lib/iomgr/workqueue_windows.h \
 src/core/lib/json/json.c \
 src/core/lib/json/json.h \
 src/core/lib/json/json_common.h \

tools/run_tests/generated/sources_and_headers.json

@@ -7904,9 +7904,6 @@
       "src/core/lib/iomgr/wakeup_fd_cv.h", 
       "src/core/lib/iomgr/wakeup_fd_pipe.h", 
       "src/core/lib/iomgr/wakeup_fd_posix.h", 
-      "src/core/lib/iomgr/workqueue.h", 
-      "src/core/lib/iomgr/workqueue_uv.h", 
-      "src/core/lib/iomgr/workqueue_windows.h", 
       "src/core/lib/json/json.h", 
       "src/core/lib/json/json_common.h", 
       "src/core/lib/json/json_reader.h", 
@@ -8113,11 +8110,6 @@
       "src/core/lib/iomgr/wakeup_fd_pipe.h", 
       "src/core/lib/iomgr/wakeup_fd_posix.c", 
       "src/core/lib/iomgr/wakeup_fd_posix.h", 
-      "src/core/lib/iomgr/workqueue.h", 
-      "src/core/lib/iomgr/workqueue_uv.c", 
-      "src/core/lib/iomgr/workqueue_uv.h", 
-      "src/core/lib/iomgr/workqueue_windows.c", 
-      "src/core/lib/iomgr/workqueue_windows.h", 
       "src/core/lib/json/json.c", 
       "src/core/lib/json/json.h", 
       "src/core/lib/json/json_common.h", 

vsprojects/vcxproj/grpc/grpc.vcxproj

@@ -374,9 +374,6 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\wakeup_fd_cv.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\wakeup_fd_pipe.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\wakeup_fd_posix.h" />
-    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue.h" />
-    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue_uv.h" />
-    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue_windows.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\json\json.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\json\json_common.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\json\json_reader.h" />
@@ -686,10 +683,6 @@
     </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\wakeup_fd_posix.c">
     </ClCompile>
-    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue_uv.c">
-    </ClCompile>
-    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue_windows.c">
-    </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\json\json.c">
     </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\json\json_reader.c">

vsprojects/vcxproj/grpc/grpc.vcxproj.filters

@@ -247,12 +247,6 @@
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\wakeup_fd_posix.c">
       <Filter>src\core\lib\iomgr</Filter>
     </ClCompile>
-    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue_uv.c">
-      <Filter>src\core\lib\iomgr</Filter>
-    </ClCompile>
-    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue_windows.c">
-      <Filter>src\core\lib\iomgr</Filter>
-    </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\json\json.c">
       <Filter>src\core\lib\json</Filter>
     </ClCompile>
@@ -1073,15 +1067,6 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\wakeup_fd_posix.h">
       <Filter>src\core\lib\iomgr</Filter>
     </ClInclude>
-    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue.h">
-      <Filter>src\core\lib\iomgr</Filter>
-    </ClInclude>
-    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue_uv.h">
-      <Filter>src\core\lib\iomgr</Filter>
-    </ClInclude>
-    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue_windows.h">
-      <Filter>src\core\lib\iomgr</Filter>
-    </ClInclude>
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\json\json.h">
       <Filter>src\core\lib\json</Filter>
     </ClInclude>

vsprojects/vcxproj/grpc_test_util/grpc_test_util.vcxproj

@@ -269,9 +269,6 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\wakeup_fd_cv.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\wakeup_fd_pipe.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\wakeup_fd_posix.h" />
-    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue.h" />
-    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue_uv.h" />
-    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue_windows.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\json\json.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\json\json_common.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\json\json_reader.h" />
@@ -513,10 +510,6 @@
     </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\wakeup_fd_posix.c">
     </ClCompile>
-    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue_uv.c">
-    </ClCompile>
-    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue_windows.c">
-    </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\json\json.c">
     </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\json\json_reader.c">

vsprojects/vcxproj/grpc_test_util/grpc_test_util.vcxproj.filters

@@ -304,12 +304,6 @@
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\wakeup_fd_posix.c">
       <Filter>src\core\lib\iomgr</Filter>
     </ClCompile>
-    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue_uv.c">
-      <Filter>src\core\lib\iomgr</Filter>
-    </ClCompile>
-    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue_windows.c">
-      <Filter>src\core\lib\iomgr</Filter>
-    </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\json\json.c">
       <Filter>src\core\lib\json</Filter>
     </ClCompile>
@@ -806,15 +800,6 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\wakeup_fd_posix.h">
       <Filter>src\core\lib\iomgr</Filter>
     </ClInclude>
-    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue.h">
-      <Filter>src\core\lib\iomgr</Filter>
-    </ClInclude>
-    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue_uv.h">
-      <Filter>src\core\lib\iomgr</Filter>
-    </ClInclude>
-    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue_windows.h">
-      <Filter>src\core\lib\iomgr</Filter>
-    </ClInclude>
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\json\json.h">
       <Filter>src\core\lib\json</Filter>
     </ClInclude>

vsprojects/vcxproj/grpc_unsecure/grpc_unsecure.vcxproj

@@ -364,9 +364,6 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\wakeup_fd_cv.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\wakeup_fd_pipe.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\wakeup_fd_posix.h" />
-    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue.h" />
-    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue_uv.h" />
-    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue_windows.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\json\json.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\json\json_common.h" />
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\json\json_reader.h" />
@@ -653,10 +650,6 @@
     </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\wakeup_fd_posix.c">
     </ClCompile>
-    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue_uv.c">
-    </ClCompile>
-    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue_windows.c">
-    </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\json\json.c">
     </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\json\json_reader.c">

vsprojects/vcxproj/grpc_unsecure/grpc_unsecure.vcxproj.filters

@@ -250,12 +250,6 @@
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\wakeup_fd_posix.c">
       <Filter>src\core\lib\iomgr</Filter>
     </ClCompile>
-    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue_uv.c">
-      <Filter>src\core\lib\iomgr</Filter>
-    </ClCompile>
-    <ClCompile Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue_windows.c">
-      <Filter>src\core\lib\iomgr</Filter>
-    </ClCompile>
     <ClCompile Include="$(SolutionDir)\..\src\core\lib\json\json.c">
       <Filter>src\core\lib\json</Filter>
     </ClCompile>
@@ -983,15 +977,6 @@
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\wakeup_fd_posix.h">
       <Filter>src\core\lib\iomgr</Filter>
     </ClInclude>
-    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue.h">
-      <Filter>src\core\lib\iomgr</Filter>
-    </ClInclude>
-    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue_uv.h">
-      <Filter>src\core\lib\iomgr</Filter>
-    </ClInclude>
-    <ClInclude Include="$(SolutionDir)\..\src\core\lib\iomgr\workqueue_windows.h">
-      <Filter>src\core\lib\iomgr</Filter>
-    </ClInclude>
     <ClInclude Include="$(SolutionDir)\..\src\core\lib\json\json.h">
       <Filter>src\core\lib\json</Filter>
     </ClInclude>