Fix edge cases resulting in close not being sent

src/core/transport/chttp2/internal.h

@@ -119,6 +119,10 @@ typedef enum {
   GRPC_WRITE_STATE_SENT_CLOSE
 } grpc_chttp2_write_state;
 
+/* flags that can be or'd into stream_global::writing_now */
+#define GRPC_CHTTP2_WRITING_DATA 1
+#define GRPC_CHTTP2_WRITING_WINDOW 2
+
 typedef enum {
   GRPC_DONT_SEND_CLOSED = 0,
   GRPC_SEND_CLOSED,
@@ -382,7 +386,7 @@ typedef struct {
   gpr_uint8 published_cancelled;
   /** is this stream in the stream map? (boolean) */
   gpr_uint8 in_stream_map;
-  /** is this stream actively being written? */
+  /** bitmask of GRPC_CHTTP2_WRITING_xxx above */
   gpr_uint8 writing_now;
 
   /** stream state already published to the upper layer */

src/core/transport/chttp2/writing.c

@@ -77,7 +77,6 @@ int grpc_chttp2_unlocking_check_writes(
 
     stream_writing->id = stream_global->id;
     stream_writing->send_closed = GRPC_DONT_SEND_CLOSED;
-    GPR_ASSERT(!stream_global->writing_now);
 
     if (stream_global->outgoing_sopb) {
       window_delta =
@@ -123,11 +122,13 @@ int grpc_chttp2_unlocking_check_writes(
       stream_global->unannounced_incoming_window = 0;
       grpc_chttp2_list_add_incoming_window_updated(transport_global,
                                                    stream_global);
-      stream_global->writing_now = 1;
-      grpc_chttp2_list_add_writing_stream(transport_writing, stream_writing);
-    } else if (stream_writing->sopb.nops > 0 ||
-               stream_writing->send_closed != GRPC_DONT_SEND_CLOSED) {
-      stream_global->writing_now = 1;
+      stream_global->writing_now |= GRPC_CHTTP2_WRITING_WINDOW;
+    }
+    if (stream_writing->sopb.nops > 0 ||
+        stream_writing->send_closed != GRPC_DONT_SEND_CLOSED) {
+      stream_global->writing_now |= GRPC_CHTTP2_WRITING_DATA;
+    }
+    if (stream_global->writing_now != 0) {
       grpc_chttp2_list_add_writing_stream(transport_writing, stream_writing);
     }
   }
@@ -183,6 +184,7 @@ static void finalize_outbuf(grpc_chttp2_transport_writing *transport_writing) {
                          stream_writing->send_closed != GRPC_DONT_SEND_CLOSED,
                          stream_writing->id, &transport_writing->hpack_compressor,
                          &transport_writing->outbuf);
+      stream_writing->sopb.nops = 0;
     }
     if (stream_writing->announce_window > 0) {
       gpr_slice_buffer_add(
@@ -191,7 +193,6 @@ static void finalize_outbuf(grpc_chttp2_transport_writing *transport_writing) {
               stream_writing->id, stream_writing->announce_window));
       stream_writing->announce_window = 0;
     }
-    stream_writing->sopb.nops = 0;
     if (stream_writing->send_closed == GRPC_SEND_CLOSED_WITH_RST_STREAM) {
       gpr_slice_buffer_add(&transport_writing->outbuf,
                            grpc_chttp2_rst_stream_create(stream_writing->id,
@@ -215,20 +216,23 @@ void grpc_chttp2_cleanup_writing(
 
   while (grpc_chttp2_list_pop_written_stream(
       transport_global, transport_writing, &stream_global, &stream_writing)) {
-    GPR_ASSERT(stream_global->writing_now);
-    stream_global->writing_now = 0;
-    if (stream_global->outgoing_sopb != NULL &&
-        stream_global->outgoing_sopb->nops == 0) {
-      stream_global->outgoing_sopb = NULL;
-      grpc_chttp2_schedule_closure(transport_global,
-                                   stream_global->send_done_closure, 1);
-    }
+    GPR_ASSERT(stream_global->writing_now != 0);
     if (stream_writing->send_closed != GRPC_DONT_SEND_CLOSED) {
       stream_global->write_state = GRPC_WRITE_STATE_SENT_CLOSE;
       if (!transport_global->is_client) {
         stream_global->read_closed = 1;
       }
     }
+    if (stream_global->writing_now & GRPC_CHTTP2_WRITING_DATA) {
+      if (stream_global->outgoing_sopb != NULL &&
+          stream_global->outgoing_sopb->nops == 0) {
+        GPR_ASSERT(stream_global->write_state != GRPC_WRITE_STATE_QUEUED_CLOSE);
+        stream_global->outgoing_sopb = NULL;
+        grpc_chttp2_schedule_closure(transport_global,
+                                     stream_global->send_done_closure, 1);
+      }
+    }
+    stream_global->writing_now = 0;
     grpc_chttp2_list_add_read_write_state_changed(transport_global,
                                                   stream_global);
   }

src/core/transport/chttp2_transport.c

@@ -855,7 +855,7 @@ static void unlock_check_read_write_state(grpc_chttp2_transport *t) {
     if (!stream_global->publish_sopb) {
       continue;
     }
-    if (stream_global->writing_now) {
+    if (stream_global->writing_now != 0) {
       continue;
     }
     /* FIXME(ctiller): we include in_stream_map in our computation of