Use a separate list for streams stalled by transport in writing path

src/core/transport/chttp2/internal.h

@@ -67,6 +67,9 @@ typedef enum {
   GRPC_CHTTP2_LIST_CLOSED_WAITING_FOR_PARSING,
   GRPC_CHTTP2_LIST_CLOSED_WAITING_FOR_WRITING,
   GRPC_CHTTP2_LIST_STALLED_BY_TRANSPORT,
+  /* streams waiting for the outgoing window in the writing path, they will be
+   * merged to the stalled list or writable list under transport lock. */
+  GRPC_CHTTP2_LIST_WRITING_STALLED_BY_TRANSPORT,
   /** streams that are waiting to start because there are too many concurrent
       streams on the connection */
   GRPC_CHTTP2_LIST_WAITING_FOR_CONCURRENCY,
@@ -504,11 +507,11 @@ void grpc_chttp2_publish_reads(grpc_exec_ctx *exec_ctx,
                                grpc_chttp2_transport_global *global,
                                grpc_chttp2_transport_parsing *parsing);
 
-/** Get a writable stream
-    returns non-zero if there was a stream available */
 void grpc_chttp2_list_add_writable_stream(
     grpc_chttp2_transport_global *transport_global,
     grpc_chttp2_stream_global *stream_global);
+/** Get a writable stream
+    returns non-zero if there was a stream available */
 int grpc_chttp2_list_pop_writable_stream(
     grpc_chttp2_transport_global *transport_global,
     grpc_chttp2_transport_writing *transport_writing,
@@ -560,9 +563,12 @@ int grpc_chttp2_list_pop_check_read_ops(
     grpc_chttp2_transport_global *transport_global,
     grpc_chttp2_stream_global **stream_global);
 
-void grpc_chttp2_list_add_stalled_by_transport(
+void grpc_chttp2_list_add_writing_stalled_by_transport(
     grpc_chttp2_transport_writing *transport_writing,
     grpc_chttp2_stream_writing *stream_writing);
+void grpc_chttp2_list_flush_writing_stalled_by_transport(
+    grpc_chttp2_transport_writing *transport_writing);
+
 int grpc_chttp2_list_pop_stalled_by_transport(
     grpc_chttp2_transport_global *transport_global,
     grpc_chttp2_stream_global **stream_global);

src/core/transport/chttp2/stream_lists.c

@@ -313,12 +313,26 @@ int grpc_chttp2_list_pop_check_read_ops(
   return r;
 }
 
-void grpc_chttp2_list_add_stalled_by_transport(
+void grpc_chttp2_list_add_writing_stalled_by_transport(
     grpc_chttp2_transport_writing *transport_writing,
     grpc_chttp2_stream_writing *stream_writing) {
   stream_list_add(TRANSPORT_FROM_WRITING(transport_writing),
                   STREAM_FROM_WRITING(stream_writing),
-                  GRPC_CHTTP2_LIST_STALLED_BY_TRANSPORT);
+                  GRPC_CHTTP2_LIST_WRITING_STALLED_BY_TRANSPORT);
+}
+
+void grpc_chttp2_list_flush_writing_stalled_by_transport(
+    grpc_chttp2_transport_writing *transport_writing) {
+  grpc_chttp2_stream *stream;
+  grpc_chttp2_transport *transport = TRANSPORT_FROM_WRITING(transport_writing);
+  while (stream_list_pop(transport, &stream,
+                         GRPC_CHTTP2_LIST_WRITING_STALLED_BY_TRANSPORT)) {
+    if (transport_writing->outgoing_window > 0) {
+      grpc_chttp2_list_add_writable_stream(&transport->global, &stream->global);
+    } else {
+      stream_list_add(transport, stream, GRPC_CHTTP2_LIST_STALLED_BY_TRANSPORT);
+    }
+  }
 }
 
 int grpc_chttp2_list_pop_stalled_by_transport(

src/core/transport/chttp2/writing.c

@@ -130,8 +130,8 @@ int grpc_chttp2_unlocking_check_writes(
             GRPC_CHTTP2_STREAM_REF(stream_global, "chttp2_writing");
           }
         } else {
-          grpc_chttp2_list_add_stalled_by_transport(transport_writing,
-                                                    stream_writing);
+          grpc_chttp2_list_add_writing_stalled_by_transport(transport_writing,
+                                                            stream_writing);
         }
       }
       if (stream_global->send_trailing_metadata) {
@@ -273,8 +273,8 @@ static void finalize_outbuf(grpc_exec_ctx *exec_ctx,
           stream_writing->sent_message = 1;
         }
       } else if (transport_writing->outgoing_window == 0) {
-        grpc_chttp2_list_add_stalled_by_transport(transport_writing,
-                                                  stream_writing);
+        grpc_chttp2_list_add_writing_stalled_by_transport(transport_writing,
+                                                          stream_writing);
         grpc_chttp2_list_add_written_stream(transport_writing, stream_writing);
       }
     }
@@ -312,8 +312,8 @@ static void finalize_outbuf(grpc_exec_ctx *exec_ctx,
           /* do nothing - already reffed */
         }
       } else {
-        grpc_chttp2_list_add_stalled_by_transport(transport_writing,
-                                                  stream_writing);
+        grpc_chttp2_list_add_writing_stalled_by_transport(transport_writing,
+                                                          stream_writing);
         grpc_chttp2_list_add_written_stream(transport_writing, stream_writing);
       }
     } else {
@@ -330,6 +330,8 @@ void grpc_chttp2_cleanup_writing(
   grpc_chttp2_stream_writing *stream_writing;
   grpc_chttp2_stream_global *stream_global;
 
+  grpc_chttp2_list_flush_writing_stalled_by_transport(transport_writing);
+
   while (grpc_chttp2_list_pop_written_stream(
       transport_global, transport_writing, &stream_global, &stream_writing)) {
     if (stream_writing->sent_initial_metadata) {