Merge pull request #15776 from sreecha/epollex-ownerfd-fix

Prevent pollable from accessing a potentially orphaned/destroyed fd

CMakeLists.txt

@@ -246,6 +246,9 @@ endif()
 add_dependencies(buildtests_c endpoint_pair_test)
 add_dependencies(buildtests_c error_test)
 if(_gRPC_PLATFORM_LINUX)
+add_dependencies(buildtests_c ev_epollex_linux_test)
+endif()
+if(_gRPC_PLATFORM_LINUX)
 add_dependencies(buildtests_c ev_epollsig_linux_test)
 endif()
 add_dependencies(buildtests_c fake_resolver_test)
@@ -6186,6 +6189,37 @@ endif (gRPC_BUILD_TESTS)
 if (gRPC_BUILD_TESTS)
 if(_gRPC_PLATFORM_LINUX)
 
+add_executable(ev_epollex_linux_test
+  test/core/iomgr/ev_epollex_linux_test.cc
+)
+
+
+target_include_directories(ev_epollex_linux_test
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include
+  PRIVATE ${_gRPC_SSL_INCLUDE_DIR}
+  PRIVATE ${_gRPC_PROTOBUF_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ZLIB_INCLUDE_DIR}
+  PRIVATE ${_gRPC_BENCHMARK_INCLUDE_DIR}
+  PRIVATE ${_gRPC_CARES_INCLUDE_DIR}
+  PRIVATE ${_gRPC_GFLAGS_INCLUDE_DIR}
+  PRIVATE ${_gRPC_ADDRESS_SORTING_INCLUDE_DIR}
+  PRIVATE ${_gRPC_NANOPB_INCLUDE_DIR}
+)
+
+target_link_libraries(ev_epollex_linux_test
+  ${_gRPC_ALLTARGETS_LIBRARIES}
+  grpc_test_util
+  grpc
+  gpr_test_util
+  gpr
+)
+
+endif()
+endif (gRPC_BUILD_TESTS)
+if (gRPC_BUILD_TESTS)
+if(_gRPC_PLATFORM_LINUX)
+
 add_executable(ev_epollsig_linux_test
   test/core/iomgr/ev_epollsig_linux_test.cc
 )

Makefile

@@ -968,6 +968,7 @@ dns_resolver_test: $(BINDIR)/$(CONFIG)/dns_resolver_test
 dualstack_socket_test: $(BINDIR)/$(CONFIG)/dualstack_socket_test
 endpoint_pair_test: $(BINDIR)/$(CONFIG)/endpoint_pair_test
 error_test: $(BINDIR)/$(CONFIG)/error_test
+ev_epollex_linux_test: $(BINDIR)/$(CONFIG)/ev_epollex_linux_test
 ev_epollsig_linux_test: $(BINDIR)/$(CONFIG)/ev_epollsig_linux_test
 fake_resolver_test: $(BINDIR)/$(CONFIG)/fake_resolver_test
 fake_transport_security_test: $(BINDIR)/$(CONFIG)/fake_transport_security_test
@@ -1413,6 +1414,7 @@ buildtests_c: privatelibs_c \
   $(BINDIR)/$(CONFIG)/dualstack_socket_test \
   $(BINDIR)/$(CONFIG)/endpoint_pair_test \
   $(BINDIR)/$(CONFIG)/error_test \
+  $(BINDIR)/$(CONFIG)/ev_epollex_linux_test \
   $(BINDIR)/$(CONFIG)/ev_epollsig_linux_test \
   $(BINDIR)/$(CONFIG)/fake_resolver_test \
   $(BINDIR)/$(CONFIG)/fake_transport_security_test \
@@ -1934,6 +1936,8 @@ test_c: buildtests_c
 	$(Q) $(BINDIR)/$(CONFIG)/endpoint_pair_test || ( echo test endpoint_pair_test failed ; exit 1 )
 	$(E) "[RUN]     Testing error_test"
 	$(Q) $(BINDIR)/$(CONFIG)/error_test || ( echo test error_test failed ; exit 1 )
+	$(E) "[RUN]     Testing ev_epollex_linux_test"
+	$(Q) $(BINDIR)/$(CONFIG)/ev_epollex_linux_test || ( echo test ev_epollex_linux_test failed ; exit 1 )
 	$(E) "[RUN]     Testing ev_epollsig_linux_test"
 	$(Q) $(BINDIR)/$(CONFIG)/ev_epollsig_linux_test || ( echo test ev_epollsig_linux_test failed ; exit 1 )
 	$(E) "[RUN]     Testing fake_resolver_test"
@@ -10998,6 +11002,38 @@ endif
 endif
 
 
+EV_EPOLLEX_LINUX_TEST_SRC = \
+    test/core/iomgr/ev_epollex_linux_test.cc \
+
+EV_EPOLLEX_LINUX_TEST_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(EV_EPOLLEX_LINUX_TEST_SRC))))
+ifeq ($(NO_SECURE),true)
+
+# You can't build secure targets if you don't have OpenSSL.
+
+$(BINDIR)/$(CONFIG)/ev_epollex_linux_test: openssl_dep_error
+
+else
+
+
+
+$(BINDIR)/$(CONFIG)/ev_epollex_linux_test: $(EV_EPOLLEX_LINUX_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libgrpc_test_util.a $(LIBDIR)/$(CONFIG)/libgrpc.a $(LIBDIR)/$(CONFIG)/libgpr_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a
+	$(E) "[LD]      Linking $@"
+	$(Q) mkdir -p `dirname $@`
+	$(Q) $(LD) $(LDFLAGS) $(EV_EPOLLEX_LINUX_TEST_OBJS) $(LIBDIR)/$(CONFIG)/libgrpc_test_util.a $(LIBDIR)/$(CONFIG)/libgrpc.a $(LIBDIR)/$(CONFIG)/libgpr_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a $(LDLIBS) $(LDLIBS_SECURE) -o $(BINDIR)/$(CONFIG)/ev_epollex_linux_test
+
+endif
+
+$(OBJDIR)/$(CONFIG)/test/core/iomgr/ev_epollex_linux_test.o:  $(LIBDIR)/$(CONFIG)/libgrpc_test_util.a $(LIBDIR)/$(CONFIG)/libgrpc.a $(LIBDIR)/$(CONFIG)/libgpr_test_util.a $(LIBDIR)/$(CONFIG)/libgpr.a
+
+deps_ev_epollex_linux_test: $(EV_EPOLLEX_LINUX_TEST_OBJS:.o=.dep)
+
+ifneq ($(NO_SECURE),true)
+ifneq ($(NO_DEPS),true)
+-include $(EV_EPOLLEX_LINUX_TEST_OBJS:.o=.dep)
+endif
+endif
+
+
 EV_EPOLLSIG_LINUX_TEST_SRC = \
     test/core/iomgr/ev_epollsig_linux_test.cc \
 

build.yaml

@@ -2260,6 +2260,21 @@ targets:
   - gpr_test_util
   - gpr
   uses_polling: false
+- name: ev_epollex_linux_test
+  cpu_cost: 3
+  build: test
+  language: c
+  src:
+  - test/core/iomgr/ev_epollex_linux_test.cc
+  deps:
+  - grpc_test_util
+  - grpc
+  - gpr_test_util
+  - gpr
+  exclude_iomgrs:
+  - uv
+  platforms:
+  - linux
 - name: ev_epollsig_linux_test
   cpu_cost: 3
   build: test

src/core/lib/iomgr/ev_epollex_linux.cc

@@ -104,8 +104,10 @@ struct pollable {
   int epfd;
   grpc_wakeup_fd wakeup;
 
-  // only for type fd... one ref to the owner fd
-  grpc_fd* owner_fd;
+  // The following are relevant only for type PO_FD
+  grpc_fd* owner_fd;       // Set to the owner_fd if the type is PO_FD
+  gpr_mu owner_orphan_mu;  // Synchronizes access to owner_orphaned field
+  bool owner_orphaned;     // Is the owner fd orphaned
 
   grpc_pollset_set* pollset_set;
   pollable* next;
@@ -338,21 +340,45 @@ static void ref_by(grpc_fd* fd, int n) {
   GPR_ASSERT(gpr_atm_no_barrier_fetch_add(&fd->refst, n) > 0);
 }
 
+#ifndef NDEBUG
+#define INVALIDATE_FD(fd) invalidate_fd(fd)
+/* Since an fd is never really destroyed (i.e gpr_free() is not called), it is
+ * hard to cases where fd fields are accessed even after calling fd_destroy().
+ * The following invalidates fd fields to make catching such errors easier */
+static void invalidate_fd(grpc_fd* fd) {
+  fd->fd = -1;
+  fd->salt = -1;
+  gpr_atm_no_barrier_store(&fd->refst, -1);
+  memset(&fd->orphan_mu, -1, sizeof(fd->orphan_mu));
+  memset(&fd->pollable_mu, -1, sizeof(fd->pollable_mu));
+  fd->pollable_obj = nullptr;
+  fd->on_done_closure = nullptr;
+  gpr_atm_no_barrier_store(&fd->read_notifier_pollset, 0);
+  memset(&fd->iomgr_object, -1, sizeof(fd->iomgr_object));
+  fd->track_err = false;
+}
+#else
+#define INVALIDATE_FD(fd)
+#endif
+
+/* Uninitialize and add to the freelist */
 static void fd_destroy(void* arg, grpc_error* error) {
   grpc_fd* fd = static_cast<grpc_fd*>(arg);
-  /* Add the fd to the freelist */
   grpc_iomgr_unregister_object(&fd->iomgr_object);
   POLLABLE_UNREF(fd->pollable_obj, "fd_pollable");
   gpr_mu_destroy(&fd->pollable_mu);
   gpr_mu_destroy(&fd->orphan_mu);
-  gpr_mu_lock(&fd_freelist_mu);
-  fd->freelist_next = fd_freelist;
-  fd_freelist = fd;
 
   fd->read_closure->DestroyEvent();
   fd->write_closure->DestroyEvent();
   fd->error_closure->DestroyEvent();
 
+  INVALIDATE_FD(fd);
+
+  /* Add the fd to the freelist */
+  gpr_mu_lock(&fd_freelist_mu);
+  fd->freelist_next = fd_freelist;
+  fd_freelist = fd;
   gpr_mu_unlock(&fd_freelist_mu);
 }
 
@@ -408,20 +434,18 @@ static grpc_fd* fd_create(int fd, const char* name, bool track_err) {
     new_fd->error_closure.Init();
   }
 
-  gpr_mu_init(&new_fd->pollable_mu);
-  gpr_mu_init(&new_fd->orphan_mu);
-  new_fd->pollable_obj = nullptr;
-  gpr_atm_rel_store(&new_fd->refst, (gpr_atm)1);
   new_fd->fd = fd;
-  new_fd->track_err = track_err;
   new_fd->salt = gpr_atm_no_barrier_fetch_add(&g_fd_salt, 1);
+  gpr_atm_rel_store(&new_fd->refst, (gpr_atm)1);
+  gpr_mu_init(&new_fd->orphan_mu);
+  gpr_mu_init(&new_fd->pollable_mu);
+  new_fd->pollable_obj = nullptr;
   new_fd->read_closure->InitEvent();
   new_fd->write_closure->InitEvent();
   new_fd->error_closure->InitEvent();
-  gpr_atm_no_barrier_store(&new_fd->read_notifier_pollset, (gpr_atm)NULL);
-
   new_fd->freelist_next = nullptr;
   new_fd->on_done_closure = nullptr;
+  gpr_atm_no_barrier_store(&new_fd->read_notifier_pollset, (gpr_atm)NULL);
 
   char* fd_name;
   gpr_asprintf(&fd_name, "%s fd=%d", name, fd);
@@ -432,6 +456,8 @@ static grpc_fd* fd_create(int fd, const char* name, bool track_err) {
   }
 #endif
   gpr_free(fd_name);
+
+  new_fd->track_err = track_err;
   return new_fd;
 }
 
@@ -446,6 +472,17 @@ static void fd_orphan(grpc_fd* fd, grpc_closure* on_done, int* release_fd,
 
   gpr_mu_lock(&fd->orphan_mu);
 
+  // Get the fd->pollable_obj and set the owner_orphaned on that pollable to
+  // true so that the pollable will no longer access its owner_fd field.
+  gpr_mu_lock(&fd->pollable_mu);
+  pollable* pollable_obj = fd->pollable_obj;
+  gpr_mu_unlock(&fd->pollable_mu);
+
+  if (pollable_obj) {
+    gpr_mu_lock(&pollable_obj->owner_orphan_mu);
+    pollable_obj->owner_orphaned = true;
+  }
+
   fd->on_done_closure = on_done;
 
   /* If release_fd is not NULL, we should be relinquishing control of the file
@@ -467,6 +504,10 @@ static void fd_orphan(grpc_fd* fd, grpc_closure* on_done, int* release_fd,
 
   GRPC_CLOSURE_SCHED(fd->on_done_closure, GRPC_ERROR_NONE);
 
+  if (pollable_obj) {
+    gpr_mu_unlock(&pollable_obj->owner_orphan_mu);
+  }
+
   gpr_mu_unlock(&fd->orphan_mu);
 
   UNREF_BY(fd, 2, reason); /* Drop the reference */
@@ -551,6 +592,8 @@ static grpc_error* pollable_create(pollable_type type, pollable** p) {
   gpr_mu_init(&(*p)->mu);
   (*p)->epfd = epfd;
   (*p)->owner_fd = nullptr;
+  gpr_mu_init(&(*p)->owner_orphan_mu);
+  (*p)->owner_orphaned = false;
   (*p)->pollset_set = nullptr;
   (*p)->next = (*p)->prev = *p;
   (*p)->root_worker = nullptr;
@@ -590,6 +633,7 @@ static void pollable_unref(pollable* p, int line, const char* reason) {
     GRPC_FD_TRACE("pollable_unref: Closing epfd: %d", p->epfd);
     close(p->epfd);
     grpc_wakeup_fd_destroy(&p->wakeup);
+    gpr_mu_destroy(&p->owner_orphan_mu);
     gpr_free(p);
   }
 }
@@ -846,10 +890,15 @@ static void fd_become_writable(grpc_fd* fd) { fd->write_closure->SetReady(); }
 
 static void fd_has_errors(grpc_fd* fd) { fd->error_closure->SetReady(); }
 
-static grpc_error* fd_get_or_become_pollable(grpc_fd* fd, pollable** p) {
+/* Get the pollable_obj attached to this fd. If none is attached, create a new
+ * pollable object (of type PO_FD), attach it to the fd and return it
+ *
+ * Note that if a pollable object is already attached to the fd, it may be of
+ * either PO_FD or PO_MULTI type */
+static grpc_error* get_fd_pollable(grpc_fd* fd, pollable** p) {
   gpr_mu_lock(&fd->pollable_mu);
   grpc_error* error = GRPC_ERROR_NONE;
-  static const char* err_desc = "fd_get_or_become_pollable";
+  static const char* err_desc = "get_fd_pollable";
   if (fd->pollable_obj == nullptr) {
     if (append_error(&error, pollable_create(PO_FD, &fd->pollable_obj),
                      err_desc)) {
@@ -1186,7 +1235,7 @@ static grpc_error* pollset_transition_pollable_from_empty_to_fd_locked(
   }
   append_error(&error, pollset_kick_all(pollset), err_desc);
   POLLABLE_UNREF(pollset->active_pollable, "pollset");
-  append_error(&error, fd_get_or_become_pollable(fd, &pollset->active_pollable),
+  append_error(&error, get_fd_pollable(fd, &pollset->active_pollable),
                err_desc);
   return error;
 }
@@ -1230,9 +1279,8 @@ static grpc_error* pollset_add_fd_locked(grpc_pollset* pollset, grpc_fd* fd) {
       error = pollset_transition_pollable_from_empty_to_fd_locked(pollset, fd);
       break;
     case PO_FD:
-      gpr_mu_lock(&po_at_start->owner_fd->orphan_mu);
-      if ((gpr_atm_no_barrier_load(&pollset->active_pollable->owner_fd->refst) &
-           1) == 0) {
+      gpr_mu_lock(&po_at_start->owner_orphan_mu);
+      if (po_at_start->owner_orphaned) {
         error =
             pollset_transition_pollable_from_empty_to_fd_locked(pollset, fd);
       } else {
@@ -1240,7 +1288,7 @@ static grpc_error* pollset_add_fd_locked(grpc_pollset* pollset, grpc_fd* fd) {
         error =
             pollset_transition_pollable_from_fd_to_multi_locked(pollset, fd);
       }
-      gpr_mu_unlock(&po_at_start->owner_fd->orphan_mu);
+      gpr_mu_unlock(&po_at_start->owner_orphan_mu);
       break;
     case PO_MULTI:
       error = pollable_add_fd(pollset->active_pollable, fd);
@@ -1276,16 +1324,17 @@ static grpc_error* pollset_as_multipollable_locked(grpc_pollset* pollset,
       append_error(&error, pollset_kick_all(pollset), err_desc);
       break;
     case PO_FD:
-      gpr_mu_lock(&po_at_start->owner_fd->orphan_mu);
-      if ((gpr_atm_no_barrier_load(&pollset->active_pollable->owner_fd->refst) &
-           1) == 0) {
+      gpr_mu_lock(&po_at_start->owner_orphan_mu);
+      if (po_at_start->owner_orphaned) {
+        // Unlock before Unref'ing the pollable
+        gpr_mu_unlock(&po_at_start->owner_orphan_mu);
         POLLABLE_UNREF(pollset->active_pollable, "pollset");
         error = pollable_create(PO_MULTI, &pollset->active_pollable);
       } else {
         error = pollset_transition_pollable_from_fd_to_multi_locked(pollset,
                                                                     nullptr);
+        gpr_mu_unlock(&po_at_start->owner_orphan_mu);
       }
-      gpr_mu_unlock(&po_at_start->owner_fd->orphan_mu);
       break;
     case PO_MULTI:
       break;

test/core/iomgr/BUILD

@@ -18,7 +18,10 @@ licenses(["notice"])  # Apache v2
 
 load("//test/core/util:grpc_fuzzer.bzl", "grpc_fuzzer")
 
-grpc_package(name = "test/core/iomgr", visibility = "public") # Useful for third party devs to test their io manager implementation.
+grpc_package(
+    name = "test/core/iomgr",
+    visibility = "public",
+)  # Useful for third party devs to test their io manager implementation.
 
 grpc_cc_library(
     name = "endpoint_tests",
@@ -72,16 +75,28 @@ grpc_cc_test(
     ],
 )
 
+grpc_cc_test(
+    name = "ev_epollex_linux_test",
+    srcs = ["ev_epollex_linux_test.cc"],
+    language = "C++",
+    deps = [
+        "//:gpr",
+        "//:grpc",
+        "//test/core/util:gpr_test_util",
+        "//test/core/util:grpc_test_util",
+    ],
+)
+
 grpc_cc_test(
     name = "ev_epollsig_linux_test",
     srcs = ["ev_epollsig_linux_test.cc"],
+    language = "C++",
     deps = [
         "//:gpr",
         "//:grpc",
         "//test/core/util:gpr_test_util",
         "//test/core/util:grpc_test_util",
     ],
-    language = "C++",
 )
 
 grpc_cc_test(
@@ -221,13 +236,13 @@ grpc_cc_test(
     name = "tcp_server_posix_test",
     srcs = ["tcp_server_posix_test.cc"],
     language = "C++",
+    tags = ["manual"],  # TODO(adelez): Remove once this works on Foundry.
     deps = [
         "//:gpr",
         "//:grpc",
         "//test/core/util:gpr_test_util",
         "//test/core/util:grpc_test_util",
     ],
-    tags = ["manual"],    # TODO(adelez): Remove once this works on Foundry.
 )
 
 grpc_cc_test(

test/core/iomgr/ev_epollex_linux_test.cc

@@ -0,0 +1,115 @@
+/*
+ *
+ * Copyright 2018 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"
+
+/* This test only relevant on linux systems where epoll() is available */
+#if defined(GRPC_LINUX_EPOLL_CREATE1) && defined(GRPC_LINUX_EVENTFD)
+#include "src/core/lib/iomgr/ev_epollex_linux.h"
+
+#include <grpc/grpc.h>
+#include <string.h>
+#include <sys/eventfd.h>
+
+#include "test/core/util/test_config.h"
+
+static void pollset_destroy(void* ps, grpc_error* error) {
+  grpc_pollset_destroy(static_cast<grpc_pollset*>(ps));
+  gpr_free(ps);
+}
+
+// This test is added to cover the case found in bug:
+// https://github.com/grpc/grpc/issues/15760
+static void test_pollable_owner_fd() {
+  grpc_core::ExecCtx exec_ctx;
+  int ev_fd1;
+  int ev_fd2;
+  grpc_fd* grpc_fd1;
+  grpc_fd* grpc_fd2;
+  grpc_pollset* ps;
+  gpr_mu* mu;
+
+  // == Create two grpc_fds ==
+  // All we need is two file descriptors. Doesn't matter what type. We use
+  // eventfd type here for the purpose of this test
+  ev_fd1 = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
+  ev_fd2 = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
+  if (ev_fd1 < 0 || ev_fd2 < 0) {
+    gpr_log(GPR_ERROR, "Error in creating event fds for the test");
+    return;
+  }
+  grpc_fd1 = grpc_fd_create(ev_fd1, "epollex-test-fd1", false);
+  grpc_fd2 = grpc_fd_create(ev_fd2, "epollex-test-fd2", false);
+  grpc_core::ExecCtx::Get()->Flush();
+
+  // == Create a pollset ==
+  ps = static_cast<grpc_pollset*>(gpr_zalloc(grpc_pollset_size()));
+  grpc_pollset_init(ps, &mu);
+  grpc_core::ExecCtx::Get()->Flush();
+
+  // == Add fd1 to pollset ==
+  grpc_pollset_add_fd(ps, grpc_fd1);
+  grpc_core::ExecCtx::Get()->Flush();
+
+  // == Destroy fd1 ==
+  grpc_fd_orphan(grpc_fd1, nullptr, nullptr, "test fd1 orphan");
+  grpc_core::ExecCtx::Get()->Flush();
+
+  // = Add fd2 to pollset ==
+  //
+  // Before https://github.com/grpc/grpc/issues/15760, the following line caused
+  // unexpected behavior (The previous grpc_pollset_add_fd(ps, grpc_fd1) created
+  // an underlying structure in epollex that held a reference to grpc_fd1 which
+  // was being accessed here even after grpc_fd_orphan(grpc_fd1) was called
+  grpc_pollset_add_fd(ps, grpc_fd2);
+  grpc_core::ExecCtx::Get()->Flush();
+
+  // == Destroy fd2 ==
+  grpc_fd_orphan(grpc_fd2, nullptr, nullptr, "test fd2 orphan");
+  grpc_core::ExecCtx::Get()->Flush();
+
+  // == Destroy pollset
+  grpc_closure ps_destroy_closure;
+  GRPC_CLOSURE_INIT(&ps_destroy_closure, pollset_destroy, ps,
+                    grpc_schedule_on_exec_ctx);
+  grpc_pollset_shutdown(ps, &ps_destroy_closure);
+  grpc_core::ExecCtx::Get()->Flush();
+}
+
+int main(int argc, char** argv) {
+  const char* poll_strategy = nullptr;
+  grpc_test_init(argc, argv);
+  grpc_init();
+  {
+    grpc_core::ExecCtx exec_ctx;
+    poll_strategy = grpc_get_poll_strategy_name();
+    if (poll_strategy != nullptr && strcmp(poll_strategy, "epollex") == 0) {
+      test_pollable_owner_fd();
+    } else {
+      gpr_log(GPR_INFO,
+              "Skipping the test. The test is only relevant for 'epollex' "
+              "strategy. and the current strategy is: '%s'",
+              poll_strategy);
+    }
+  }
+
+  grpc_shutdown();
+  return 0;
+}
+#else /* defined(GRPC_LINUX_EPOLL_CREATE1) && defined(GRPC_LINUX_EVENTFD) */
+int main(int argc, char** argv) { return 0; }
+#endif

tools/run_tests/generated/sources_and_headers.json

@@ -449,6 +449,23 @@
     "third_party": false, 
     "type": "target"
   }, 
+  {
+    "deps": [
+      "gpr", 
+      "gpr_test_util", 
+      "grpc", 
+      "grpc_test_util"
+    ], 
+    "headers": [], 
+    "is_filegroup": false, 
+    "language": "c", 
+    "name": "ev_epollex_linux_test", 
+    "src": [
+      "test/core/iomgr/ev_epollex_linux_test.cc"
+    ], 
+    "third_party": false, 
+    "type": "target"
+  }, 
   {
     "deps": [
       "gpr", 

tools/run_tests/generated/tests.json

@@ -561,6 +561,26 @@
     ], 
     "uses_polling": false
   }, 
+  {
+    "args": [], 
+    "benchmark": false, 
+    "ci_platforms": [
+      "linux"
+    ], 
+    "cpu_cost": 3, 
+    "exclude_configs": [], 
+    "exclude_iomgrs": [
+      "uv"
+    ], 
+    "flaky": false, 
+    "gtest": false, 
+    "language": "c", 
+    "name": "ev_epollex_linux_test", 
+    "platforms": [
+      "linux"
+    ], 
+    "uses_polling": true
+  }, 
   {
     "args": [], 
     "benchmark": false,