Merge remote-tracking branch 'upstream/master' into max_send_size_filter

5 files changed, 374 insertions, 488 deletions

diff --git a/src/core/ext/transport/chttp2/transport/chttp2_transport.c b/src/core/ext/transport/chttp2/transport/chttp2_transport.c
index 00b7fc4cc2..ef731657af 100644
--- a/src/core/ext/transport/chttp2/transport/chttp2_transport.c
+++ b/src/core/ext/transport/chttp2/transport/chttp2_transport.c
@@ -91,13 +91,20 @@ static const grpc_transport_vtable vtable;
 static void writing_action(grpc_exec_ctx *exec_ctx, void *t, grpc_error *error);
 static void reading_action(grpc_exec_ctx *exec_ctx, void *t, grpc_error *error);
 static void parsing_action(grpc_exec_ctx *exec_ctx, void *t, grpc_error *error);
-static void initiate_writing(grpc_exec_ctx *exec_ctx, void *t,
-                             grpc_error *error);
+static void reading_action_locked(grpc_exec_ctx *exec_ctx, void *arg,
+                                  grpc_error *error);
+static void post_parse_locked(grpc_exec_ctx *exec_ctx, void *arg,
+                              grpc_error *error);
+static void initiate_writing_locked(grpc_exec_ctx *exec_ctx, void *t,
+                                    grpc_error *error);
+static void initiate_read_flush_locked(grpc_exec_ctx *exec_ctx, void *t,
+                                       grpc_error *error);
+static void terminate_writing_with_lock(grpc_exec_ctx *exec_ctx, void *t,
+                                        grpc_error *error);
 
 static void start_writing(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t);
 static void end_waiting_for_write(grpc_exec_ctx *exec_ctx,
-                                  grpc_chttp2_transport *t, grpc_error *error,
-                                  const char *reason);
+                                  grpc_chttp2_transport *t, grpc_error *error);
 
 /** Set a transport level setting, and push it to our peer */
 static void push_setting(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
@@ -107,11 +114,6 @@ static void push_setting(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
 static void drop_connection(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
                             grpc_error *error);
 
-/** Perform a transport_op */
-static void perform_stream_op_locked(grpc_exec_ctx *exec_ctx,
-                                     grpc_chttp2_transport *t,
-                                     grpc_chttp2_stream *s, void *transport_op);
-
 /** Cancel a stream: coming from the transport API */
 static void cancel_from_api(grpc_exec_ctx *exec_ctx,
                             grpc_chttp2_transport_global *transport_global,
@@ -123,22 +125,10 @@ static void close_from_api(grpc_exec_ctx *exec_ctx,
                            grpc_chttp2_stream_global *stream_global,
                            grpc_error *error);
 
-/** Add endpoint from this transport to pollset */
-static void add_to_pollset_locked(grpc_exec_ctx *exec_ctx,
-                                  grpc_chttp2_transport *t,
-                                  grpc_chttp2_stream *s_ignored, void *pollset);
-static void add_to_pollset_set_locked(grpc_exec_ctx *exec_ctx,
-                                      grpc_chttp2_transport *t,
-                                      grpc_chttp2_stream *s_ignored,
-                                      void *pollset_set);
-
 /** Start new streams that have been created if we can */
 static void maybe_start_some_streams(
     grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_global *transport_global);
 
-static void finish_global_actions(grpc_exec_ctx *exec_ctx,
-                                  grpc_chttp2_transport *t);
-
 static void connectivity_state_set(
     grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_global *transport_global,
     grpc_connectivity_state state, grpc_error *error, const char *reason);
@@ -151,14 +141,16 @@ static void incoming_byte_stream_update_flow_control(
     grpc_chttp2_stream_global *stream_global, size_t max_size_hint,
     size_t have_already);
 static void incoming_byte_stream_destroy_locked(grpc_exec_ctx *exec_ctx,
-                                                grpc_chttp2_transport *t,
-                                                grpc_chttp2_stream *s,
-                                                void *byte_stream);
+                                                void *byte_stream,
+                                                grpc_error *error_ignored);
 static void fail_pending_writes(grpc_exec_ctx *exec_ctx,
                                 grpc_chttp2_transport_global *transport_global,
                                 grpc_chttp2_stream_global *stream_global,
                                 grpc_error *error);
 
+static void set_write_state(grpc_chttp2_transport *t,
+                            grpc_chttp2_write_state state, const char *reason);
+
 /*******************************************************************************
  * CONSTRUCTION/DESTRUCTION/REFCOUNTING
  */
@@ -167,9 +159,7 @@ static void destruct_transport(grpc_exec_ctx *exec_ctx,
                                grpc_chttp2_transport *t) {
   size_t i;
 
-  gpr_mu_lock(&t->executor.mu);
-
-  GPR_ASSERT(t->ep == NULL);
+  grpc_endpoint_destroy(exec_ctx, t->ep);
 
   gpr_slice_buffer_destroy(&t->global.qbuf);
 
@@ -193,8 +183,7 @@ static void destruct_transport(grpc_exec_ctx *exec_ctx,
   grpc_chttp2_stream_map_destroy(&t->new_stream_map);
   grpc_connectivity_state_destroy(exec_ctx, &t->channel_callback.state_tracker);
 
-  gpr_mu_unlock(&t->executor.mu);
-  gpr_mu_destroy(&t->executor.mu);
+  grpc_combiner_destroy(exec_ctx, t->executor.combiner);
 
   /* callback remaining pings: they're not allowed to call into the transpot,
      and maybe they hold resources that need to be freed */
@@ -252,12 +241,13 @@ static void init_transport(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
   memset(t, 0, sizeof(*t));
 
   t->base.vtable = &vtable;
+  t->executor.write_state = GRPC_CHTTP2_WRITES_CORKED;
   t->ep = ep;
-  /* one ref is for destroy, the other for when ep becomes NULL */
-  gpr_ref_init(&t->refs, 2);
+  /* one ref is for destroy */
+  gpr_ref_init(&t->refs, 1);
   /* ref is dropped at transport close() */
   gpr_ref_init(&t->shutdown_ep_refs, 1);
-  gpr_mu_init(&t->executor.mu);
+  t->executor.combiner = grpc_combiner_create(grpc_endpoint_get_workqueue(ep));
   t->peer_string = grpc_endpoint_get_peer(ep);
   t->endpoint_reading = 1;
   t->global.next_stream_id = is_client ? 1 : 2;
@@ -283,23 +273,22 @@ static void init_transport(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
   grpc_chttp2_hpack_compressor_init(&t->writing.hpack_compressor);
   grpc_closure_init(&t->writing_action, writing_action, t);
   grpc_closure_init(&t->reading_action, reading_action, t);
+  grpc_closure_init(&t->reading_action_locked, reading_action_locked, t);
   grpc_closure_init(&t->parsing_action, parsing_action, t);
-  grpc_closure_init(&t->initiate_writing, initiate_writing, t);
+  grpc_closure_init(&t->post_parse_locked, post_parse_locked, t);
+  grpc_closure_init(&t->initiate_writing, initiate_writing_locked, t);
+  grpc_closure_init(&t->terminate_writing, terminate_writing_with_lock, t);
+  grpc_closure_init(&t->initiate_read_flush_locked, initiate_read_flush_locked,
+                    t);
+  grpc_closure_init(&t->writing.done_cb, grpc_chttp2_terminate_writing,
+                    &t->writing);
 
   gpr_slice_buffer_init(&t->parsing.qbuf);
   grpc_chttp2_goaway_parser_init(&t->parsing.goaway_parser);
   grpc_chttp2_hpack_parser_init(&t->parsing.hpack_parser);
 
-  grpc_closure_init(&t->writing.done_cb, grpc_chttp2_terminate_writing,
-                    &t->writing);
   gpr_slice_buffer_init(&t->read_buffer);
 
-  if (is_client) {
-    gpr_slice_buffer_add(
-        &t->global.qbuf,
-        gpr_slice_from_copied_string(GRPC_CHTTP2_CLIENT_CONNECT_STRING));
-    grpc_chttp2_initiate_write(exec_ctx, &t->global, false, "initial_write");
-  }
   /* 8 is a random stab in the dark as to a good initial size: it's small enough
      that it shouldn't waste memory for infrequently used connections, yet
      large enough that the exponential growth should happen nicely when it's
@@ -322,6 +311,13 @@ static void init_transport(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
   t->global.force_send_settings = 1 << GRPC_CHTTP2_SETTINGS_INITIAL_WINDOW_SIZE;
   t->global.sent_local_settings = 0;
 
+  if (is_client) {
+    gpr_slice_buffer_add(
+        &t->writing.outbuf,
+        gpr_slice_from_copied_string(GRPC_CHTTP2_CLIENT_CONNECT_STRING));
+    grpc_chttp2_initiate_write(exec_ctx, &t->global, false, "initial_write");
+  }
+
   /* configure http2 the way we like it */
   if (is_client) {
     push_setting(exec_ctx, t, GRPC_CHTTP2_SETTINGS_ENABLE_PUSH, 0);
@@ -415,47 +411,39 @@ static void init_transport(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
       }
     }
   }
+
+  set_write_state(t, GRPC_CHTTP2_WRITING_INACTIVE, "uncork");
+  grpc_chttp2_initiate_write(exec_ctx, &t->global, false, "init");
 }
 
-static void destroy_transport_locked(grpc_exec_ctx *exec_ctx,
-                                     grpc_chttp2_transport *t,
-                                     grpc_chttp2_stream *s_ignored,
-                                     void *arg_ignored) {
+static void destroy_transport_locked(grpc_exec_ctx *exec_ctx, void *tp,
+                                     grpc_error *error) {
+  grpc_chttp2_transport *t = tp;
   t->destroying = 1;
   drop_connection(exec_ctx, t, GRPC_ERROR_CREATE("Transport destroyed"));
+  UNREF_TRANSPORT(exec_ctx, t, "destroy");
 }
 
 static void destroy_transport(grpc_exec_ctx *exec_ctx, grpc_transport *gt) {
   grpc_chttp2_transport *t = (grpc_chttp2_transport *)gt;
-  grpc_chttp2_run_with_global_lock(exec_ctx, t, NULL, destroy_transport_locked,
-                                   NULL, 0);
-  UNREF_TRANSPORT(exec_ctx, t, "destroy");
+  grpc_combiner_execute(exec_ctx, t->executor.combiner,
+                        grpc_closure_create(destroy_transport_locked, t),
+                        GRPC_ERROR_NONE);
 }
 
 /** block grpc_endpoint_shutdown being called until a paired
     allow_endpoint_shutdown is made */
 static void prevent_endpoint_shutdown(grpc_chttp2_transport *t) {
-  GPR_ASSERT(t->ep);
   gpr_ref(&t->shutdown_ep_refs);
 }
 
 static void allow_endpoint_shutdown_locked(grpc_exec_ctx *exec_ctx,
                                            grpc_chttp2_transport *t) {
   if (gpr_unref(&t->shutdown_ep_refs)) {
-    if (t->ep) {
-      grpc_endpoint_shutdown(exec_ctx, t->ep);
-    }
+    grpc_endpoint_shutdown(exec_ctx, t->ep);
   }
 }
 
-static void destroy_endpoint(grpc_exec_ctx *exec_ctx,
-                             grpc_chttp2_transport *t) {
-  grpc_endpoint_destroy(exec_ctx, t->ep);
-  t->ep = NULL;
-  /* safe because we'll still have the ref for write */
-  UNREF_TRANSPORT(exec_ctx, t, "disconnect");
-}
-
 static void close_transport_locked(grpc_exec_ctx *exec_ctx,
                                    grpc_chttp2_transport *t,
                                    grpc_error *error) {
@@ -466,9 +454,7 @@ static void close_transport_locked(grpc_exec_ctx *exec_ctx,
     t->closed = 1;
     connectivity_state_set(exec_ctx, &t->global, GRPC_CHANNEL_SHUTDOWN,
                            GRPC_ERROR_REF(error), "close_transport");
-    if (t->ep) {
-      allow_endpoint_shutdown_locked(exec_ctx, t);
-    }
+    allow_endpoint_shutdown_locked(exec_ctx, t);
 
     /* flush writable stream list to avoid dangling references */
     grpc_chttp2_stream_global *stream_global;
@@ -502,21 +488,23 @@ void grpc_chttp2_stream_unref(grpc_exec_ctx *exec_ctx,
 }
 #endif
 
-static void finish_init_stream_locked(grpc_exec_ctx *exec_ctx,
-                                      grpc_chttp2_transport *t,
-                                      grpc_chttp2_stream *s,
-                                      void *arg_ignored) {
-  grpc_chttp2_register_stream(t, s);
+static void finish_init_stream_locked(grpc_exec_ctx *exec_ctx, void *sp,
+                                      grpc_error *error) {
+  grpc_chttp2_stream *s = sp;
+  grpc_chttp2_register_stream(s->t, s);
+  GRPC_CHTTP2_STREAM_UNREF(exec_ctx, &s->global, "init");
 }
 
 static int init_stream(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
                        grpc_stream *gs, grpc_stream_refcount *refcount,
                        const void *server_data) {
+  GPR_TIMER_BEGIN("init_stream", 0);
   grpc_chttp2_transport *t = (grpc_chttp2_transport *)gt;
   grpc_chttp2_stream *s = (grpc_chttp2_stream *)gs;
 
   memset(s, 0, sizeof(*s));
 
+  s->t = t;
   s->refcount = refcount;
   /* We reserve one 'active stream' that's dropped when the stream is
      read-closed. The others are for incoming_byte_streams that are actively
@@ -551,16 +539,21 @@ static int init_stream(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
     s->global.in_stream_map = true;
   }
 
-  grpc_chttp2_run_with_global_lock(exec_ctx, t, s, finish_init_stream_locked,
-                                   NULL, 0);
+  grpc_closure_init(&s->init_stream, finish_init_stream_locked, s);
+  GRPC_CHTTP2_STREAM_REF(&s->global, "init");
+  grpc_combiner_execute(exec_ctx, t->executor.combiner, &s->init_stream,
+                        GRPC_ERROR_NONE);
+
+  GPR_TIMER_END("init_stream", 0);
 
   return 0;
 }
 
-static void destroy_stream_locked(grpc_exec_ctx *exec_ctx,
-                                  grpc_chttp2_transport *t,
-                                  grpc_chttp2_stream *s, void *arg) {
+static void destroy_stream_locked(grpc_exec_ctx *exec_ctx, void *sp,
+                                  grpc_error *error) {
   grpc_byte_stream *bs;
+  grpc_chttp2_stream *s = sp;
+  grpc_chttp2_transport *t = s->t;
 
   GPR_TIMER_BEGIN("destroy_stream", 0);
 
@@ -579,7 +572,7 @@ static void destroy_stream_locked(grpc_exec_ctx *exec_ctx,
 
   while (
       (bs = grpc_chttp2_incoming_frame_queue_pop(&s->global.incoming_frames))) {
-    incoming_byte_stream_destroy_locked(exec_ctx, NULL, NULL, bs);
+    incoming_byte_stream_destroy_locked(exec_ctx, bs, GRPC_ERROR_NONE);
   }
 
   grpc_chttp2_list_remove_unannounced_incoming_window_available(&t->global,
@@ -616,16 +609,20 @@ static void destroy_stream_locked(grpc_exec_ctx *exec_ctx,
 
   GPR_TIMER_END("destroy_stream", 0);
 
-  gpr_free(arg);
+  gpr_free(s->destroy_stream_arg);
 }
 
 static void destroy_stream(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
                            grpc_stream *gs, void *and_free_memory) {
+  GPR_TIMER_BEGIN("destroy_stream", 0);
   grpc_chttp2_transport *t = (grpc_chttp2_transport *)gt;
   grpc_chttp2_stream *s = (grpc_chttp2_stream *)gs;
 
-  grpc_chttp2_run_with_global_lock(exec_ctx, t, s, destroy_stream_locked,
-                                   and_free_memory, 0);
+  s->destroy_stream_arg = and_free_memory;
+  grpc_closure_init(&s->destroy_stream, destroy_stream_locked, s);
+  grpc_combiner_execute(exec_ctx, t->executor.combiner, &s->destroy_stream,
+                        GRPC_ERROR_NONE);
+  GPR_TIMER_END("destroy_stream", 0);
 }
 
 grpc_chttp2_stream_parsing *grpc_chttp2_parsing_lookup_stream(
@@ -656,12 +653,10 @@ grpc_chttp2_stream_parsing *grpc_chttp2_parsing_accept_stream(
 
 static const char *write_state_name(grpc_chttp2_write_state state) {
   switch (state) {
+    case GRPC_CHTTP2_WRITES_CORKED:
+      return "CORKED";
     case GRPC_CHTTP2_WRITING_INACTIVE:
       return "INACTIVE";
-    case GRPC_CHTTP2_WRITE_REQUESTED_NO_POLLER:
-      return "REQUESTED[p=0]";
-    case GRPC_CHTTP2_WRITE_REQUESTED_WITH_POLLER:
-      return "REQUESTED[p=1]";
     case GRPC_CHTTP2_WRITE_SCHEDULED:
       return "SCHEDULED";
     case GRPC_CHTTP2_WRITING:
@@ -684,120 +679,18 @@ static void set_write_state(grpc_chttp2_transport *t,
   t->executor.write_state = state;
 }
 
-static void finish_global_actions(grpc_exec_ctx *exec_ctx,
-                                  grpc_chttp2_transport *t) {
-  grpc_chttp2_executor_action_header *hdr;
-  grpc_chttp2_executor_action_header *next;
-
-  GPR_TIMER_BEGIN("finish_global_actions", 0);
-
-  for (;;) {
-    check_read_ops(exec_ctx, &t->global);
-
-    gpr_mu_lock(&t->executor.mu);
-    if (t->executor.pending_actions_head != NULL) {
-      hdr = t->executor.pending_actions_head;
-      t->executor.pending_actions_head = t->executor.pending_actions_tail =
-          NULL;
-      gpr_mu_unlock(&t->executor.mu);
-      while (hdr != NULL) {
-        GPR_TIMER_BEGIN("chttp2:locked_action", 0);
-        hdr->action(exec_ctx, t, hdr->stream, hdr->arg);
-        GPR_TIMER_END("chttp2:locked_action", 0);
-        next = hdr->next;
-        gpr_free(hdr);
-        UNREF_TRANSPORT(exec_ctx, t, "pending_action");
-        hdr = next;
-      }
-      continue;
-    } else {
-      t->executor.global_active = false;
-      switch (t->executor.write_state) {
-        case GRPC_CHTTP2_WRITE_REQUESTED_WITH_POLLER:
-          set_write_state(t, GRPC_CHTTP2_WRITE_SCHEDULED, "unlocking");
-          REF_TRANSPORT(t, "initiate_writing");
-          gpr_mu_unlock(&t->executor.mu);
-          grpc_exec_ctx_sched(
-              exec_ctx, &t->initiate_writing, GRPC_ERROR_NONE,
-              t->ep != NULL ? grpc_endpoint_get_workqueue(t->ep) : NULL);
-          break;
-        case GRPC_CHTTP2_WRITE_REQUESTED_NO_POLLER:
-          start_writing(exec_ctx, t);
-          gpr_mu_unlock(&t->executor.mu);
-          break;
-        case GRPC_CHTTP2_WRITING_INACTIVE:
-        case GRPC_CHTTP2_WRITING:
-        case GRPC_CHTTP2_WRITING_STALE_WITH_POLLER:
-        case GRPC_CHTTP2_WRITING_STALE_NO_POLLER:
-        case GRPC_CHTTP2_WRITE_SCHEDULED:
-          gpr_mu_unlock(&t->executor.mu);
-          break;
-      }
-    }
-    break;
-  }
-
-  GPR_TIMER_END("finish_global_actions", 0);
+static void initiate_writing_locked(grpc_exec_ctx *exec_ctx, void *tp,
+                                    grpc_error *error) {
+  grpc_chttp2_transport *t = tp;
+  GPR_ASSERT(t->executor.write_state == GRPC_CHTTP2_WRITE_SCHEDULED);
+  start_writing(exec_ctx, t);
 }
 
-void grpc_chttp2_run_with_global_lock(grpc_exec_ctx *exec_ctx,
-                                      grpc_chttp2_transport *t,
-                                      grpc_chttp2_stream *optional_stream,
-                                      grpc_chttp2_locked_action action,
-                                      void *arg, size_t sizeof_arg) {
-  grpc_chttp2_executor_action_header *hdr;
-
-  GPR_TIMER_BEGIN("grpc_chttp2_run_with_global_lock", 0);
-
-  REF_TRANSPORT(t, "run_global");
-  gpr_mu_lock(&t->executor.mu);
-
-  for (;;) {
-    if (!t->executor.global_active) {
-      t->executor.global_active = 1;
-      gpr_mu_unlock(&t->executor.mu);
-
-      GPR_TIMER_BEGIN("chttp2:locked_action", 0);
-      action(exec_ctx, t, optional_stream, arg);
-      GPR_TIMER_END("chttp2:locked_action", 0);
-
-      finish_global_actions(exec_ctx, t);
-    } else {
-      gpr_mu_unlock(&t->executor.mu);
-
-      hdr = gpr_malloc(sizeof(*hdr) + sizeof_arg);
-      hdr->stream = optional_stream;
-      hdr->action = action;
-      if (sizeof_arg == 0) {
-        hdr->arg = arg;
-      } else {
-        hdr->arg = hdr + 1;
-        memcpy(hdr->arg, arg, sizeof_arg);
-      }
-
-      gpr_mu_lock(&t->executor.mu);
-      if (!t->executor.global_active) {
-        /* global lock was released while allocating memory: release & retry */
-        gpr_free(hdr);
-        continue;
-      }
-      hdr->next = NULL;
-      if (t->executor.pending_actions_head != NULL) {
-        t->executor.pending_actions_tail =
-            t->executor.pending_actions_tail->next = hdr;
-      } else {
-        t->executor.pending_actions_tail = t->executor.pending_actions_head =
-            hdr;
-      }
-      REF_TRANSPORT(t, "pending_action");
-      gpr_mu_unlock(&t->executor.mu);
-    }
-    break;
-  }
-
-  UNREF_TRANSPORT(exec_ctx, t, "run_global");
-
-  GPR_TIMER_END("grpc_chttp2_run_with_global_lock", 0);
+static void initiate_read_flush_locked(grpc_exec_ctx *exec_ctx, void *tp,
+                                       grpc_error *error) {
+  grpc_chttp2_transport *t = tp;
+  t->executor.check_read_ops_scheduled = false;
+  check_read_ops(exec_ctx, &t->global);
 }
 
 /*******************************************************************************
@@ -807,11 +700,12 @@ void grpc_chttp2_run_with_global_lock(grpc_exec_ctx *exec_ctx,
 void grpc_chttp2_initiate_write(grpc_exec_ctx *exec_ctx,
                                 grpc_chttp2_transport_global *transport_global,
                                 bool covered_by_poller, const char *reason) {
+  GPR_TIMER_BEGIN("grpc_chttp2_initiate_write", 0);
+
   /* Perform state checks, and transition to a scheduled state if appropriate.
-     Each time we finish the global lock execution, we check if we need to
-     write. If we do:
-      - (if there is a poller surrounding the write) schedule
-        initiate_writing, which locks and calls initiate_writing_locked to...
+     If we are inactive, schedule a write chain to begin once the transport
+     combiner finishes any executions in its current batch (which may be
+     scheduled AFTER this code executes). The write chain will:
       - call start_writing, which verifies (under the global lock) that there
         are things that need to be written by calling
         grpc_chttp2_unlocking_check_writes, and if so schedules writing_action
@@ -821,31 +715,28 @@ void grpc_chttp2_initiate_write(grpc_exec_ctx *exec_ctx,
         to do *another* write immediately, and if so loops back to
         start_writing.
 
-      Current problems:
+     Current problems:
        - too much lock entry/exiting
        - the writing thread can become stuck indefinitely (punt through the
          workqueue periodically to fix) */
 
   grpc_chttp2_transport *t = TRANSPORT_FROM_GLOBAL(transport_global);
   switch (t->executor.write_state) {
-    case GRPC_CHTTP2_WRITING_INACTIVE:
-      set_write_state(t, covered_by_poller
-                             ? GRPC_CHTTP2_WRITE_REQUESTED_WITH_POLLER
-                             : GRPC_CHTTP2_WRITE_REQUESTED_NO_POLLER,
-                      reason);
+    case GRPC_CHTTP2_WRITES_CORKED:
       break;
-    case GRPC_CHTTP2_WRITE_REQUESTED_WITH_POLLER:
-      /* nothing to do: write already requested */
+    case GRPC_CHTTP2_WRITING_INACTIVE:
+      set_write_state(t, GRPC_CHTTP2_WRITE_SCHEDULED, reason);
+      REF_TRANSPORT(t, "writing");
+      grpc_combiner_execute_finally(exec_ctx, t->executor.combiner,
+                                    &t->initiate_writing, GRPC_ERROR_NONE,
+                                    covered_by_poller);
       break;
-    case GRPC_CHTTP2_WRITE_REQUESTED_NO_POLLER:
+    case GRPC_CHTTP2_WRITE_SCHEDULED:
       if (covered_by_poller) {
         /* upgrade to note poller is available to cover the write */
-        set_write_state(t, GRPC_CHTTP2_WRITE_REQUESTED_WITH_POLLER, reason);
+        grpc_combiner_force_async_finally(t->executor.combiner);
       }
       break;
-    case GRPC_CHTTP2_WRITE_SCHEDULED:
-      /* nothing to do: write already scheduled */
-      break;
     case GRPC_CHTTP2_WRITING:
       set_write_state(t,
                       covered_by_poller ? GRPC_CHTTP2_WRITING_STALE_WITH_POLLER
@@ -862,15 +753,15 @@ void grpc_chttp2_initiate_write(grpc_exec_ctx *exec_ctx,
       }
       break;
   }
+  GPR_TIMER_END("grpc_chttp2_initiate_write", 0);
 }
 
 static void start_writing(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t) {
-  GPR_ASSERT(t->executor.write_state == GRPC_CHTTP2_WRITE_SCHEDULED ||
-             t->executor.write_state == GRPC_CHTTP2_WRITE_REQUESTED_NO_POLLER);
+  GPR_TIMER_BEGIN("start_writing", 0);
+  GPR_ASSERT(t->executor.write_state == GRPC_CHTTP2_WRITE_SCHEDULED);
   if (!t->closed &&
       grpc_chttp2_unlocking_check_writes(exec_ctx, &t->global, &t->writing)) {
     set_write_state(t, GRPC_CHTTP2_WRITING, "start_writing");
-    REF_TRANSPORT(t, "writing");
     prevent_endpoint_shutdown(t);
     grpc_exec_ctx_sched(exec_ctx, &t->writing_action, GRPC_ERROR_NONE, NULL);
   } else {
@@ -881,25 +772,10 @@ static void start_writing(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t) {
       set_write_state(t, GRPC_CHTTP2_WRITING_INACTIVE,
                       "start_writing:nothing_to_write");
     }
-    end_waiting_for_write(exec_ctx, t, GRPC_ERROR_NONE, "Nothing to write");
-    if (t->ep && !t->endpoint_reading) {
-      destroy_endpoint(exec_ctx, t);
-    }
+    end_waiting_for_write(exec_ctx, t, GRPC_ERROR_NONE);
+    UNREF_TRANSPORT(exec_ctx, t, "writing");
   }
-}
-
-static void initiate_writing_locked(grpc_exec_ctx *exec_ctx,
-                                    grpc_chttp2_transport *t,
-                                    grpc_chttp2_stream *s_unused,
-                                    void *arg_ignored) {
-  start_writing(exec_ctx, t);
-  UNREF_TRANSPORT(exec_ctx, t, "initiate_writing");
-}
-
-static void initiate_writing(grpc_exec_ctx *exec_ctx, void *arg,
-                             grpc_error *error) {
-  grpc_chttp2_run_with_global_lock(exec_ctx, arg, NULL, initiate_writing_locked,
-                                   NULL, 0);
+  GPR_TIMER_END("start_writing", 0);
 }
 
 void grpc_chttp2_become_writable(grpc_exec_ctx *exec_ctx,
@@ -933,15 +809,10 @@ static void push_setting(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
 /* error may be GRPC_ERROR_NONE if there is no error allocated yet.
    In that case, use "reason" as the text for a new error. */
 static void end_waiting_for_write(grpc_exec_ctx *exec_ctx,
-                                  grpc_chttp2_transport *t, grpc_error *error,
-                                  const char *reason) {
+                                  grpc_chttp2_transport *t, grpc_error *error) {
   grpc_chttp2_stream_global *stream_global;
   while (grpc_chttp2_list_pop_closed_waiting_for_writing(&t->global,
                                                          &stream_global)) {
-    if (error == GRPC_ERROR_NONE && reason != NULL) {
-      /* create error object. */
-      error = GRPC_ERROR_CREATE(reason);
-    }
     fail_pending_writes(exec_ctx, &t->global, stream_global,
                         GRPC_ERROR_REF(error));
     GRPC_CHTTP2_STREAM_UNREF(exec_ctx, stream_global, "finish_writes");
@@ -949,12 +820,10 @@ static void end_waiting_for_write(grpc_exec_ctx *exec_ctx,
   GRPC_ERROR_UNREF(error);
 }
 
-static void terminate_writing_with_lock(grpc_exec_ctx *exec_ctx,
-                                        grpc_chttp2_transport *t,
-                                        grpc_chttp2_stream *s_ignored,
-                                        void *a) {
-  grpc_error *error = a;
-
+static void terminate_writing_with_lock(grpc_exec_ctx *exec_ctx, void *tp,
+                                        grpc_error *error) {
+  GPR_TIMER_BEGIN("terminate_writing_with_lock", 0);
+  grpc_chttp2_transport *t = tp;
   allow_endpoint_shutdown_locked(exec_ctx, t);
 
   if (error != GRPC_ERROR_NONE) {
@@ -963,39 +832,46 @@ static void terminate_writing_with_lock(grpc_exec_ctx *exec_ctx,
 
   grpc_chttp2_cleanup_writing(exec_ctx, &t->global, &t->writing);
 
-  end_waiting_for_write(exec_ctx, t, error, NULL);
+  end_waiting_for_write(exec_ctx, t, GRPC_ERROR_REF(error));
 
   switch (t->executor.write_state) {
+    case GRPC_CHTTP2_WRITES_CORKED:
     case GRPC_CHTTP2_WRITING_INACTIVE:
-    case GRPC_CHTTP2_WRITE_REQUESTED_WITH_POLLER:
-    case GRPC_CHTTP2_WRITE_REQUESTED_NO_POLLER:
     case GRPC_CHTTP2_WRITE_SCHEDULED:
       GPR_UNREACHABLE_CODE(break);
     case GRPC_CHTTP2_WRITING:
+      GPR_TIMER_MARK("state=writing", 0);
       set_write_state(t, GRPC_CHTTP2_WRITING_INACTIVE, "terminate_writing");
       break;
     case GRPC_CHTTP2_WRITING_STALE_WITH_POLLER:
-      set_write_state(t, GRPC_CHTTP2_WRITE_REQUESTED_WITH_POLLER,
-                      "terminate_writing");
+      GPR_TIMER_MARK("state=writing_stale_with_poller", 0);
+      set_write_state(t, GRPC_CHTTP2_WRITE_SCHEDULED, "terminate_writing");
+      REF_TRANSPORT(t, "writing");
+      grpc_combiner_execute_finally(exec_ctx, t->executor.combiner,
+                                    &t->initiate_writing, GRPC_ERROR_NONE,
+                                    true);
       break;
     case GRPC_CHTTP2_WRITING_STALE_NO_POLLER:
-      set_write_state(t, GRPC_CHTTP2_WRITE_REQUESTED_NO_POLLER,
-                      "terminate_writing");
+      GPR_TIMER_MARK("state=writing_stale_no_poller", 0);
+      set_write_state(t, GRPC_CHTTP2_WRITE_SCHEDULED, "terminate_writing");
+      REF_TRANSPORT(t, "writing");
+      grpc_combiner_execute_finally(exec_ctx, t->executor.combiner,
+                                    &t->initiate_writing, GRPC_ERROR_NONE,
+                                    false);
       break;
   }
 
-  if (t->ep && !t->endpoint_reading) {
-    destroy_endpoint(exec_ctx, t);
-  }
-
   UNREF_TRANSPORT(exec_ctx, t, "writing");
+  GPR_TIMER_END("terminate_writing_with_lock", 0);
 }
 
 void grpc_chttp2_terminate_writing(grpc_exec_ctx *exec_ctx,
                                    void *transport_writing, grpc_error *error) {
+  GPR_TIMER_BEGIN("grpc_chttp2_terminate_writing", 0);
   grpc_chttp2_transport *t = TRANSPORT_FROM_WRITING(transport_writing);
-  grpc_chttp2_run_with_global_lock(
-      exec_ctx, t, NULL, terminate_writing_with_lock, GRPC_ERROR_REF(error), 0);
+  grpc_combiner_execute(exec_ctx, t->executor.combiner, &t->terminate_writing,
+                        GRPC_ERROR_REF(error));
+  GPR_TIMER_END("grpc_chttp2_terminate_writing", 0);
 }
 
 static void writing_action(grpc_exec_ctx *exec_ctx, void *gt,
@@ -1139,15 +1015,22 @@ static int contains_non_ok_status(
 
 static void do_nothing(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *error) {}
 
-static void perform_stream_op_locked(grpc_exec_ctx *exec_ctx,
-                                     grpc_chttp2_transport *t,
-                                     grpc_chttp2_stream *s, void *stream_op) {
+static void perform_stream_op_locked(grpc_exec_ctx *exec_ctx, void *stream_op,
+                                     grpc_error *error_ignored) {
   GPR_TIMER_BEGIN("perform_stream_op_locked", 0);
 
   grpc_transport_stream_op *op = stream_op;
+  grpc_chttp2_transport *t = op->transport_private.args[0];
+  grpc_chttp2_stream *s = op->transport_private.args[1];
   grpc_chttp2_transport_global *transport_global = &t->global;
   grpc_chttp2_stream_global *stream_global = &s->global;
 
+  if (grpc_http_trace) {
+    char *str = grpc_transport_stream_op_string(op);
+    gpr_log(GPR_DEBUG, "perform_stream_op_locked: %s", str);
+    gpr_free(str);
+  }
+
   grpc_closure *on_complete = op->on_complete;
   if (on_complete == NULL) {
     on_complete = grpc_closure_create(do_nothing, NULL);
@@ -1202,7 +1085,8 @@ static void perform_stream_op_locked(grpc_exec_ctx *exec_ctx,
     } else {
       if (contains_non_ok_status(transport_global, op->send_initial_metadata)) {
         stream_global->seen_error = true;
-        grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
+        grpc_chttp2_list_add_check_read_ops(exec_ctx, transport_global,
+                                            stream_global);
       }
       if (!stream_global->write_closed) {
         if (transport_global->is_client) {
@@ -1269,7 +1153,8 @@ static void perform_stream_op_locked(grpc_exec_ctx *exec_ctx,
       if (contains_non_ok_status(transport_global,
                                  op->send_trailing_metadata)) {
         stream_global->seen_error = true;
-        grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
+        grpc_chttp2_list_add_check_read_ops(exec_ctx, transport_global,
+                                            stream_global);
       }
       if (stream_global->write_closed) {
         stream_global->send_trailing_metadata = NULL;
@@ -1294,7 +1179,8 @@ static void perform_stream_op_locked(grpc_exec_ctx *exec_ctx,
     stream_global->recv_initial_metadata_ready =
         op->recv_initial_metadata_ready;
     stream_global->recv_initial_metadata = op->recv_initial_metadata;
-    grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
+    grpc_chttp2_list_add_check_read_ops(exec_ctx, transport_global,
+                                        stream_global);
   }
 
   if (op->recv_message != NULL) {
@@ -1308,7 +1194,8 @@ static void perform_stream_op_locked(grpc_exec_ctx *exec_ctx,
           exec_ctx, transport_global, stream_global,
           transport_global->stream_lookahead, 0);
     }
-    grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
+    grpc_chttp2_list_add_check_read_ops(exec_ctx, transport_global,
+                                        stream_global);
   }
 
   if (op->recv_trailing_metadata != NULL) {
@@ -1317,21 +1204,30 @@ static void perform_stream_op_locked(grpc_exec_ctx *exec_ctx,
         add_closure_barrier(on_complete);
     stream_global->recv_trailing_metadata = op->recv_trailing_metadata;
     stream_global->final_metadata_requested = true;
-    grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
+    grpc_chttp2_list_add_check_read_ops(exec_ctx, transport_global,
+                                        stream_global);
   }
 
   grpc_chttp2_complete_closure_step(exec_ctx, transport_global, stream_global,
                                     &on_complete, GRPC_ERROR_NONE);
 
   GPR_TIMER_END("perform_stream_op_locked", 0);
+  GRPC_CHTTP2_STREAM_UNREF(exec_ctx, &s->global, "perform_stream_op");
 }
 
 static void perform_stream_op(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
                               grpc_stream *gs, grpc_transport_stream_op *op) {
+  GPR_TIMER_BEGIN("perform_stream_op", 0);
   grpc_chttp2_transport *t = (grpc_chttp2_transport *)gt;
   grpc_chttp2_stream *s = (grpc_chttp2_stream *)gs;
-  grpc_chttp2_run_with_global_lock(exec_ctx, t, s, perform_stream_op_locked, op,
-                                   sizeof(*op));
+  grpc_closure_init(&op->transport_private.closure, perform_stream_op_locked,
+                    op);
+  op->transport_private.args[0] = gt;
+  op->transport_private.args[1] = gs;
+  GRPC_CHTTP2_STREAM_REF(&s->global, "perform_stream_op");
+  grpc_combiner_execute(exec_ctx, t->executor.combiner,
+                        &op->transport_private.closure, GRPC_ERROR_NONE);
+  GPR_TIMER_END("perform_stream_op", 0);
 }
 
 static void send_ping_locked(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
@@ -1353,13 +1249,20 @@ static void send_ping_locked(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
   grpc_chttp2_initiate_write(exec_ctx, &t->global, true, "send_ping");
 }
 
-static void ack_ping_locked(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
-                            grpc_chttp2_stream *s, void *opaque_8bytes) {
+typedef struct ack_ping_args {
+  grpc_closure closure;
+  grpc_chttp2_transport *t;
+  uint8_t opaque_8bytes[8];
+} ack_ping_args;
+
+static void ack_ping_locked(grpc_exec_ctx *exec_ctx, void *a,
+                            grpc_error *error_ignored) {
+  ack_ping_args *args = a;
   grpc_chttp2_outstanding_ping *ping;
-  grpc_chttp2_transport_global *transport_global = &t->global;
+  grpc_chttp2_transport_global *transport_global = &args->t->global;
   for (ping = transport_global->pings.next; ping != &transport_global->pings;
        ping = ping->next) {
-    if (0 == memcmp(opaque_8bytes, ping->id, 8)) {
+    if (0 == memcmp(args->opaque_8bytes, ping->id, 8)) {
       grpc_exec_ctx_sched(exec_ctx, ping->on_recv, GRPC_ERROR_NONE, NULL);
       ping->next->prev = ping->prev;
       ping->prev->next = ping->next;
@@ -1367,21 +1270,27 @@ static void ack_ping_locked(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
       break;
     }
   }
+  UNREF_TRANSPORT(exec_ctx, args->t, "ack_ping");
+  gpr_free(args);
 }
 
 void grpc_chttp2_ack_ping(grpc_exec_ctx *exec_ctx,
                           grpc_chttp2_transport_parsing *transport_parsing,
                           const uint8_t *opaque_8bytes) {
-  grpc_chttp2_run_with_global_lock(
-      exec_ctx, TRANSPORT_FROM_PARSING(transport_parsing), NULL,
-      ack_ping_locked, (void *)opaque_8bytes, 8);
+  ack_ping_args *args = gpr_malloc(sizeof(*args));
+  args->t = TRANSPORT_FROM_PARSING(transport_parsing);
+  memcpy(args->opaque_8bytes, opaque_8bytes, sizeof(args->opaque_8bytes));
+  grpc_closure_init(&args->closure, ack_ping_locked, args);
+  REF_TRANSPORT(args->t, "ack_ping");
+  grpc_combiner_execute(exec_ctx, args->t->executor.combiner, &args->closure,
+                        GRPC_ERROR_NONE);
 }
 
 static void perform_transport_op_locked(grpc_exec_ctx *exec_ctx,
-                                        grpc_chttp2_transport *t,
-                                        grpc_chttp2_stream *s_unused,
-                                        void *stream_op) {
+                                        void *stream_op,
+                                        grpc_error *error_ignored) {
   grpc_transport_op *op = stream_op;
+  grpc_chttp2_transport *t = op->transport_private.args[0];
   grpc_error *close_transport = op->disconnect_with_error;
 
   /* If there's a set_accept_stream ensure that we're not parsing
@@ -1393,8 +1302,6 @@ static void perform_transport_op_locked(grpc_exec_ctx *exec_ctx,
     return;
   }
 
-  grpc_exec_ctx_sched(exec_ctx, op->on_consumed, GRPC_ERROR_NONE, NULL);
-
   if (op->on_connectivity_state_change != NULL) {
     grpc_connectivity_state_notify_on_state_change(
         exec_ctx, &t->channel_callback.state_tracker, op->connectivity_state,
@@ -1420,11 +1327,11 @@ static void perform_transport_op_locked(grpc_exec_ctx *exec_ctx,
   }
 
   if (op->bind_pollset) {
-    add_to_pollset_locked(exec_ctx, t, NULL, op->bind_pollset);
+    grpc_endpoint_add_to_pollset(exec_ctx, t->ep, op->bind_pollset);
   }
 
   if (op->bind_pollset_set) {
-    add_to_pollset_set_locked(exec_ctx, t, NULL, op->bind_pollset_set);
+    grpc_endpoint_add_to_pollset_set(exec_ctx, t->ep, op->bind_pollset_set);
   }
 
   if (op->send_ping) {
@@ -1434,13 +1341,21 @@ static void perform_transport_op_locked(grpc_exec_ctx *exec_ctx,
   if (close_transport != GRPC_ERROR_NONE) {
     close_transport_locked(exec_ctx, t, close_transport);
   }
+
+  grpc_exec_ctx_sched(exec_ctx, op->on_consumed, GRPC_ERROR_NONE, NULL);
+
+  UNREF_TRANSPORT(exec_ctx, t, "transport_op");
 }
 
 static void perform_transport_op(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
                                  grpc_transport_op *op) {
   grpc_chttp2_transport *t = (grpc_chttp2_transport *)gt;
-  grpc_chttp2_run_with_global_lock(
-      exec_ctx, t, NULL, perform_transport_op_locked, op, sizeof(*op));
+  op->transport_private.args[0] = gt;
+  grpc_closure_init(&op->transport_private.closure, perform_transport_op_locked,
+                    op);
+  REF_TRANSPORT(t, "transport_op");
+  grpc_combiner_execute(exec_ctx, t->executor.combiner,
+                        &op->transport_private.closure, GRPC_ERROR_NONE);
 }
 
 /*******************************************************************************
@@ -1449,6 +1364,7 @@ static void perform_transport_op(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
 
 static void check_read_ops(grpc_exec_ctx *exec_ctx,
                            grpc_chttp2_transport_global *transport_global) {
+  GPR_TIMER_BEGIN("check_read_ops", 0);
   grpc_chttp2_stream_global *stream_global;
   grpc_byte_stream *bs;
   while (
@@ -1458,7 +1374,7 @@ static void check_read_ops(grpc_exec_ctx *exec_ctx,
       if (stream_global->seen_error) {
         while ((bs = grpc_chttp2_incoming_frame_queue_pop(
                     &stream_global->incoming_frames)) != NULL) {
-          incoming_byte_stream_destroy_locked(exec_ctx, NULL, NULL, bs);
+          incoming_byte_stream_destroy_locked(exec_ctx, bs, GRPC_ERROR_NONE);
         }
         if (stream_global->exceeded_metadata_size) {
           cancel_from_api(
@@ -1481,7 +1397,7 @@ static void check_read_ops(grpc_exec_ctx *exec_ctx,
              stream_global->seen_error &&
              (bs = grpc_chttp2_incoming_frame_queue_pop(
                   &stream_global->incoming_frames)) != NULL) {
-        incoming_byte_stream_destroy_locked(exec_ctx, NULL, NULL, bs);
+        incoming_byte_stream_destroy_locked(exec_ctx, bs, GRPC_ERROR_NONE);
       }
       if (stream_global->incoming_frames.head != NULL) {
         *stream_global->recv_message = grpc_chttp2_incoming_frame_queue_pop(
@@ -1502,7 +1418,7 @@ static void check_read_ops(grpc_exec_ctx *exec_ctx,
       if (stream_global->seen_error) {
         while ((bs = grpc_chttp2_incoming_frame_queue_pop(
                     &stream_global->incoming_frames)) != NULL) {
-          incoming_byte_stream_destroy_locked(exec_ctx, NULL, NULL, bs);
+          incoming_byte_stream_destroy_locked(exec_ctx, bs, GRPC_ERROR_NONE);
         }
         if (stream_global->exceeded_metadata_size) {
           cancel_from_api(
@@ -1523,6 +1439,7 @@ static void check_read_ops(grpc_exec_ctx *exec_ctx,
       }
     }
   }
+  GPR_TIMER_END("check_read_ops", 0);
 }
 
 static void decrement_active_streams_locked(
@@ -1530,7 +1447,8 @@ static void decrement_active_streams_locked(
     grpc_chttp2_stream_global *stream_global) {
   if ((stream_global->all_incoming_byte_streams_finished =
            gpr_unref(&stream_global->active_streams))) {
-    grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
+    grpc_chttp2_list_add_check_read_ops(exec_ctx, transport_global,
+                                        stream_global);
   }
 }
 
@@ -1634,7 +1552,8 @@ static void cancel_from_api(grpc_exec_ctx *exec_ctx,
   }
   if (due_to_error != GRPC_ERROR_NONE && !stream_global->seen_error) {
     stream_global->seen_error = true;
-    grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
+    grpc_chttp2_list_add_check_read_ops(exec_ctx, transport_global,
+                                        stream_global);
   }
   grpc_chttp2_mark_stream_closed(exec_ctx, transport_global, stream_global, 1,
                                  1, due_to_error);
@@ -1646,7 +1565,8 @@ void grpc_chttp2_fake_status(grpc_exec_ctx *exec_ctx,
                              grpc_status_code status, gpr_slice *slice) {
   if (status != GRPC_STATUS_OK) {
     stream_global->seen_error = true;
-    grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
+    grpc_chttp2_list_add_check_read_ops(exec_ctx, transport_global,
+                                        stream_global);
   }
   /* stream_global->recv_trailing_metadata_finished gives us a
      last chance replacement: we've received trailing metadata,
@@ -1670,7 +1590,8 @@ void grpc_chttp2_fake_status(grpc_exec_ctx *exec_ctx,
               grpc_mdstr_from_slice(gpr_slice_ref(*slice))));
     }
     stream_global->published_trailing_metadata = true;
-    grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
+    grpc_chttp2_list_add_check_read_ops(exec_ctx, transport_global,
+                                        stream_global);
   }
   if (slice) {
     gpr_slice_unref(*slice);
@@ -1730,7 +1651,8 @@ void grpc_chttp2_mark_stream_closed(
     GRPC_ERROR_UNREF(error);
     return;
   }
-  grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
+  grpc_chttp2_list_add_check_read_ops(exec_ctx, transport_global,
+                                      stream_global);
   if (close_reads && !stream_global->read_closed) {
     stream_global->read_closed_error = GRPC_ERROR_REF(error);
     stream_global->read_closed = true;
@@ -1911,6 +1833,10 @@ static void end_all_the_calls(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
 
 static void drop_connection(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
                             grpc_error *error) {
+  if (!grpc_error_get_int(error, GRPC_ERROR_INT_GRPC_STATUS, NULL)) {
+    error = grpc_error_set_int(error, GRPC_ERROR_INT_GRPC_STATUS,
+                               GRPC_STATUS_UNAVAILABLE);
+  }
   close_transport_locked(exec_ctx, t, GRPC_ERROR_REF(error));
   end_all_the_calls(exec_ctx, t, error);
 }
@@ -1946,16 +1872,12 @@ static void update_global_window(void *args, uint32_t id, void *stream) {
  * INPUT PROCESSING - PARSING
  */
 
-static void reading_action_locked(grpc_exec_ctx *exec_ctx,
-                                  grpc_chttp2_transport *t,
-                                  grpc_chttp2_stream *s_unused, void *arg);
 static void parsing_action(grpc_exec_ctx *exec_ctx, void *arg,
                            grpc_error *error);
-static void post_reading_action_locked(grpc_exec_ctx *exec_ctx,
-                                       grpc_chttp2_transport *t,
-                                       grpc_chttp2_stream *s_unused, void *arg);
-static void post_parse_locked(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
-                              grpc_chttp2_stream *s_unused, void *arg);
+static void post_reading_action_locked(grpc_exec_ctx *exec_ctx, void *arg,
+                                       grpc_error *error);
+static void post_parse_locked(grpc_exec_ctx *exec_ctx, void *arg,
+                              grpc_error *error);
 
 static void reading_action(grpc_exec_ctx *exec_ctx, void *tp,
                            grpc_error *error) {
@@ -1963,16 +1885,20 @@ static void reading_action(grpc_exec_ctx *exec_ctx, void *tp,
      reading_action_locked ->
        (parse_unlocked -> post_parse_locked)? ->
        post_reading_action_locked */
-  grpc_chttp2_run_with_global_lock(exec_ctx, tp, NULL, reading_action_locked,
-                                   GRPC_ERROR_REF(error), 0);
+  GPR_TIMER_BEGIN("reading_action", 0);
+  grpc_chttp2_transport *t = tp;
+  grpc_combiner_execute(exec_ctx, t->executor.combiner,
+                        &t->reading_action_locked, GRPC_ERROR_REF(error));
+  GPR_TIMER_END("reading_action", 0);
 }
 
-static void reading_action_locked(grpc_exec_ctx *exec_ctx,
-                                  grpc_chttp2_transport *t,
-                                  grpc_chttp2_stream *s_unused, void *arg) {
+static void reading_action_locked(grpc_exec_ctx *exec_ctx, void *tp,
+                                  grpc_error *error) {
+  GPR_TIMER_BEGIN("reading_action_locked", 0);
+
+  grpc_chttp2_transport *t = tp;
   grpc_chttp2_transport_global *transport_global = &t->global;
   grpc_chttp2_transport_parsing *transport_parsing = &t->parsing;
-  grpc_error *error = arg;
 
   GPR_ASSERT(!t->executor.parsing_active);
   if (!t->closed) {
@@ -1981,10 +1907,13 @@ static void reading_action_locked(grpc_exec_ctx *exec_ctx,
     grpc_chttp2_stream_map_move_into(&t->new_stream_map,
                                      &t->parsing_stream_map);
     grpc_chttp2_prepare_to_read(transport_global, transport_parsing);
-    grpc_exec_ctx_sched(exec_ctx, &t->parsing_action, error, NULL);
+    grpc_exec_ctx_sched(exec_ctx, &t->parsing_action, GRPC_ERROR_REF(error),
+                        NULL);
   } else {
-    post_reading_action_locked(exec_ctx, t, s_unused, arg);
+    post_reading_action_locked(exec_ctx, t, error);
   }
+
+  GPR_TIMER_END("reading_action_locked", 0);
 }
 
 static grpc_error *try_http_parsing(grpc_exec_ctx *exec_ctx,
@@ -2036,13 +1965,15 @@ static void parsing_action(grpc_exec_ctx *exec_ctx, void *arg,
   for (i = 0; i < GPR_ARRAY_SIZE(errors); i++) {
     GRPC_ERROR_UNREF(errors[i]);
   }
+  grpc_combiner_execute(exec_ctx, t->executor.combiner, &t->post_parse_locked,
+                        err);
   GPR_TIMER_END("reading_action.parse", 0);
-  grpc_chttp2_run_with_global_lock(exec_ctx, t, NULL, post_parse_locked, err,
-                                   0);
 }
 
-static void post_parse_locked(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
-                              grpc_chttp2_stream *s_unused, void *arg) {
+static void post_parse_locked(grpc_exec_ctx *exec_ctx, void *arg,
+                              grpc_error *error) {
+  GPR_TIMER_BEGIN("post_parse_locked", 0);
+  grpc_chttp2_transport *t = arg;
   grpc_chttp2_transport_global *transport_global = &t->global;
   grpc_chttp2_transport_parsing *transport_parsing = &t->parsing;
   /* copy parsing qbuf to global qbuf */
@@ -2068,7 +1999,7 @@ static void post_parse_locked(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
   if (t->post_parsing_op) {
     grpc_transport_op *op = t->post_parsing_op;
     t->post_parsing_op = NULL;
-    perform_transport_op_locked(exec_ctx, t, NULL, op);
+    perform_transport_op_locked(exec_ctx, op, GRPC_ERROR_NONE);
     gpr_free(op);
   }
   /* if a stream is in the stream map, and gets cancelled, we need to
@@ -2085,39 +2016,32 @@ static void post_parse_locked(grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t,
     GRPC_CHTTP2_STREAM_UNREF(exec_ctx, stream_global, "chttp2");
   }
 
-  post_reading_action_locked(exec_ctx, t, s_unused, arg);
+  post_reading_action_locked(exec_ctx, t, error);
+  GPR_TIMER_END("post_parse_locked", 0);
 }
 
-static void post_reading_action_locked(grpc_exec_ctx *exec_ctx,
-                                       grpc_chttp2_transport *t,
-                                       grpc_chttp2_stream *s_unused,
-                                       void *arg) {
-  grpc_error *error = arg;
+static void post_reading_action_locked(grpc_exec_ctx *exec_ctx, void *arg,
+                                       grpc_error *error) {
+  GPR_TIMER_BEGIN("post_reading_action_locked", 0);
+  grpc_chttp2_transport *t = arg;
   bool keep_reading = false;
+  GRPC_ERROR_REF(error);
   if (error == GRPC_ERROR_NONE && t->closed) {
     error = GRPC_ERROR_CREATE("Transport closed");
   }
   if (error != GRPC_ERROR_NONE) {
-    if (!grpc_error_get_int(error, GRPC_ERROR_INT_GRPC_STATUS, NULL)) {
-      error = grpc_error_set_int(error, GRPC_ERROR_INT_GRPC_STATUS,
-                                 GRPC_STATUS_UNAVAILABLE);
-    }
     drop_connection(exec_ctx, t, GRPC_ERROR_REF(error));
     t->endpoint_reading = 0;
     if (grpc_http_write_state_trace) {
       gpr_log(GPR_DEBUG, "R:%p -> 0 ws=%s", t,
               write_state_name(t->executor.write_state));
     }
-    if (t->executor.write_state == GRPC_CHTTP2_WRITING_INACTIVE && t->ep) {
-      destroy_endpoint(exec_ctx, t);
-    }
   } else if (!t->closed) {
     keep_reading = true;
     REF_TRANSPORT(t, "keep_reading");
     prevent_endpoint_shutdown(t);
   }
   gpr_slice_buffer_reset_and_unref(&t->read_buffer);
-  GRPC_ERROR_UNREF(error);
 
   if (keep_reading) {
     grpc_endpoint_read(exec_ctx, t->ep, &t->read_buffer, &t->reading_action);
@@ -2126,6 +2050,9 @@ static void post_reading_action_locked(grpc_exec_ctx *exec_ctx,
   } else {
     UNREF_TRANSPORT(exec_ctx, t, "reading_action");
   }
+  GRPC_ERROR_UNREF(error);
+
+  GPR_TIMER_END("post_reading_action_locked", 0);
 }
 
 /*******************************************************************************
@@ -2147,36 +2074,16 @@ static void connectivity_state_set(
  * POLLSET STUFF
  */
 
-static void add_to_pollset_locked(grpc_exec_ctx *exec_ctx,
-                                  grpc_chttp2_transport *t,
-                                  grpc_chttp2_stream *s_unused, void *pollset) {
-  if (t->ep) {
-    grpc_endpoint_add_to_pollset(exec_ctx, t->ep, pollset);
-  }
-}
-
-static void add_to_pollset_set_locked(grpc_exec_ctx *exec_ctx,
-                                      grpc_chttp2_transport *t,
-                                      grpc_chttp2_stream *s_unused,
-                                      void *pollset_set) {
-  if (t->ep) {
-    grpc_endpoint_add_to_pollset_set(exec_ctx, t->ep, pollset_set);
-  }
-}
-
 static void set_pollset(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
                         grpc_stream *gs, grpc_pollset *pollset) {
-  /* TODO(ctiller): keep pollset alive */
-  grpc_chttp2_run_with_global_lock(exec_ctx, (grpc_chttp2_transport *)gt,
-                                   (grpc_chttp2_stream *)gs,
-                                   add_to_pollset_locked, pollset, 0);
+  grpc_chttp2_transport *t = (grpc_chttp2_transport *)gt;
+  grpc_endpoint_add_to_pollset(exec_ctx, t->ep, pollset);
 }
 
 static void set_pollset_set(grpc_exec_ctx *exec_ctx, grpc_transport *gt,
                             grpc_stream *gs, grpc_pollset_set *pollset_set) {
-  grpc_chttp2_run_with_global_lock(exec_ctx, (grpc_chttp2_transport *)gt,
-                                   (grpc_chttp2_stream *)gs,
-                                   add_to_pollset_set_locked, pollset_set, 0);
+  grpc_chttp2_transport *t = (grpc_chttp2_transport *)gt;
+  grpc_endpoint_add_to_pollset_set(exec_ctx, t->ep, pollset_set);
 }
 
 /*******************************************************************************
@@ -2188,6 +2095,7 @@ static void incoming_byte_stream_unref(grpc_exec_ctx *exec_ctx,
   if (gpr_unref(&bs->refs)) {
     GRPC_ERROR_UNREF(bs->error);
     gpr_slice_buffer_destroy(&bs->slices);
+    gpr_mu_destroy(&bs->slice_mu);
     gpr_free(bs);
   }
 }
@@ -2233,38 +2141,34 @@ static void incoming_byte_stream_update_flow_control(
   }
 }
 
-typedef struct {
-  grpc_chttp2_incoming_byte_stream *byte_stream;
-  gpr_slice *slice;
-  size_t max_size_hint;
-  grpc_closure *on_complete;
-} incoming_byte_stream_next_arg;
-
 static void incoming_byte_stream_next_locked(grpc_exec_ctx *exec_ctx,
-                                             grpc_chttp2_transport *t,
-                                             grpc_chttp2_stream *s,
-                                             void *argp) {
-  incoming_byte_stream_next_arg *arg = argp;
-  grpc_chttp2_incoming_byte_stream *bs =
-      (grpc_chttp2_incoming_byte_stream *)arg->byte_stream;
+                                             void *argp,
+                                             grpc_error *error_ignored) {
+  grpc_chttp2_incoming_byte_stream *bs = argp;
   grpc_chttp2_transport_global *transport_global = &bs->transport->global;
   grpc_chttp2_stream_global *stream_global = &bs->stream->global;
 
   if (bs->is_tail) {
-    incoming_byte_stream_update_flow_control(exec_ctx, transport_global,
-                                             stream_global, arg->max_size_hint,
-                                             bs->slices.length);
-  }
+    gpr_mu_lock(&bs->slice_mu);
+    size_t cur_length = bs->slices.length;
+    gpr_mu_unlock(&bs->slice_mu);
+    incoming_byte_stream_update_flow_control(
+        exec_ctx, transport_global, stream_global,
+        bs->next_action.max_size_hint, cur_length);
+  }
+  gpr_mu_lock(&bs->slice_mu);
   if (bs->slices.count > 0) {
-    *arg->slice = gpr_slice_buffer_take_first(&bs->slices);
-    grpc_exec_ctx_sched(exec_ctx, arg->on_complete, GRPC_ERROR_NONE, NULL);
-  } else if (bs->error != GRPC_ERROR_NONE) {
-    grpc_exec_ctx_sched(exec_ctx, arg->on_complete, GRPC_ERROR_REF(bs->error),
+    *bs->next_action.slice = gpr_slice_buffer_take_first(&bs->slices);
+    grpc_exec_ctx_sched(exec_ctx, bs->next_action.on_complete, GRPC_ERROR_NONE,
                         NULL);
+  } else if (bs->error != GRPC_ERROR_NONE) {
+    grpc_exec_ctx_sched(exec_ctx, bs->next_action.on_complete,
+                        GRPC_ERROR_REF(bs->error), NULL);
   } else {
-    bs->on_next = arg->on_complete;
-    bs->next = arg->slice;
+    bs->on_next = bs->next_action.on_complete;
+    bs->next = bs->next_action.slice;
   }
+  gpr_mu_unlock(&bs->slice_mu);
   incoming_byte_stream_unref(exec_ctx, bs);
 }
 
@@ -2272,13 +2176,18 @@ static int incoming_byte_stream_next(grpc_exec_ctx *exec_ctx,
                                      grpc_byte_stream *byte_stream,
                                      gpr_slice *slice, size_t max_size_hint,
                                      grpc_closure *on_complete) {
+  GPR_TIMER_BEGIN("incoming_byte_stream_next", 0);
   grpc_chttp2_incoming_byte_stream *bs =
       (grpc_chttp2_incoming_byte_stream *)byte_stream;
-  incoming_byte_stream_next_arg arg = {bs, slice, max_size_hint, on_complete};
   gpr_ref(&bs->refs);
-  grpc_chttp2_run_with_global_lock(exec_ctx, bs->transport, bs->stream,
-                                   incoming_byte_stream_next_locked, &arg,
-                                   sizeof(arg));
+  bs->next_action.slice = slice;
+  bs->next_action.max_size_hint = max_size_hint;
+  bs->next_action.on_complete = on_complete;
+  grpc_closure_init(&bs->next_action.closure, incoming_byte_stream_next_locked,
+                    bs);
+  grpc_combiner_execute(exec_ctx, bs->transport->executor.combiner,
+                        &bs->next_action.closure, GRPC_ERROR_NONE);
+  GPR_TIMER_END("incoming_byte_stream_next", 0);
   return 0;
 }
 
@@ -2286,9 +2195,8 @@ static void incoming_byte_stream_destroy(grpc_exec_ctx *exec_ctx,
                                          grpc_byte_stream *byte_stream);
 
 static void incoming_byte_stream_destroy_locked(grpc_exec_ctx *exec_ctx,
-                                                grpc_chttp2_transport *t,
-                                                grpc_chttp2_stream *s,
-                                                void *byte_stream) {
+                                                void *byte_stream,
+                                                grpc_error *error_ignored) {
   grpc_chttp2_incoming_byte_stream *bs = byte_stream;
   GPR_ASSERT(bs->base.destroy == incoming_byte_stream_destroy);
   decrement_active_streams_locked(exec_ctx, &bs->transport->global,
@@ -2298,10 +2206,14 @@ static void incoming_byte_stream_destroy_locked(grpc_exec_ctx *exec_ctx,
 
 static void incoming_byte_stream_destroy(grpc_exec_ctx *exec_ctx,
                                          grpc_byte_stream *byte_stream) {
+  GPR_TIMER_BEGIN("incoming_byte_stream_destroy", 0);
   grpc_chttp2_incoming_byte_stream *bs =
       (grpc_chttp2_incoming_byte_stream *)byte_stream;
-  grpc_chttp2_run_with_global_lock(exec_ctx, bs->transport, bs->stream,
-                                   incoming_byte_stream_destroy_locked, bs, 0);
+  grpc_closure_init(&bs->destroy_action, incoming_byte_stream_destroy_locked,
+                    bs);
+  grpc_combiner_execute(exec_ctx, bs->transport->executor.combiner,
+                        &bs->destroy_action, GRPC_ERROR_NONE);
+  GPR_TIMER_END("incoming_byte_stream_destroy", 0);
 }
 
 typedef struct {
@@ -2309,90 +2221,45 @@ typedef struct {
   gpr_slice slice;
 } incoming_byte_stream_push_arg;
 
-static void incoming_byte_stream_push_locked(grpc_exec_ctx *exec_ctx,
-                                             grpc_chttp2_transport *t,
-                                             grpc_chttp2_stream *s,
-                                             void *argp) {
-  incoming_byte_stream_push_arg *arg = argp;
-  grpc_chttp2_incoming_byte_stream *bs = arg->byte_stream;
+void grpc_chttp2_incoming_byte_stream_push(grpc_exec_ctx *exec_ctx,
+                                           grpc_chttp2_incoming_byte_stream *bs,
+                                           gpr_slice slice) {
+  gpr_mu_lock(&bs->slice_mu);
   if (bs->on_next != NULL) {
-    *bs->next = arg->slice;
+    *bs->next = slice;
     grpc_exec_ctx_sched(exec_ctx, bs->on_next, GRPC_ERROR_NONE, NULL);
     bs->on_next = NULL;
   } else {
-    gpr_slice_buffer_add(&bs->slices, arg->slice);
+    gpr_slice_buffer_add(&bs->slices, slice);
   }
-  incoming_byte_stream_unref(exec_ctx, bs);
+  gpr_mu_unlock(&bs->slice_mu);
 }
 
-void grpc_chttp2_incoming_byte_stream_push(grpc_exec_ctx *exec_ctx,
-                                           grpc_chttp2_incoming_byte_stream *bs,
-                                           gpr_slice slice) {
-  incoming_byte_stream_push_arg arg = {bs, slice};
-  gpr_ref(&bs->refs);
-  grpc_chttp2_run_with_global_lock(exec_ctx, bs->transport, bs->stream,
-                                   incoming_byte_stream_push_locked, &arg,
-                                   sizeof(arg));
-}
-
-typedef struct {
-  grpc_chttp2_incoming_byte_stream *bs;
-  grpc_error *error;
-} bs_fail_args;
-
-static bs_fail_args *make_bs_fail_args(grpc_chttp2_incoming_byte_stream *bs,
-                                       grpc_error *error) {
-  bs_fail_args *a = gpr_malloc(sizeof(*a));
-  a->bs = bs;
-  a->error = error;
-  return a;
-}
-
-static void incoming_byte_stream_finished_failed_locked(
-    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport *t, grpc_chttp2_stream *s,
-    void *argp) {
-  bs_fail_args *a = argp;
-  grpc_chttp2_incoming_byte_stream *bs = a->bs;
-  grpc_error *error = a->error;
-  gpr_free(a);
-  grpc_exec_ctx_sched(exec_ctx, bs->on_next, GRPC_ERROR_REF(error), NULL);
-  bs->on_next = NULL;
-  GRPC_ERROR_UNREF(bs->error);
-  bs->error = error;
-  incoming_byte_stream_unref(exec_ctx, bs);
-}
-
-static void incoming_byte_stream_finished_ok_locked(grpc_exec_ctx *exec_ctx,
-                                                    grpc_chttp2_transport *t,
-                                                    grpc_chttp2_stream *s,
-                                                    void *argp) {
-  grpc_chttp2_incoming_byte_stream *bs = argp;
+static void incoming_byte_stream_finished_locked(grpc_exec_ctx *exec_ctx,
+                                                 void *bsp, grpc_error *error) {
+  grpc_chttp2_incoming_byte_stream *bs = bsp;
+  if (error != GRPC_ERROR_NONE) {
+    grpc_exec_ctx_sched(exec_ctx, bs->on_next, GRPC_ERROR_REF(error), NULL);
+    bs->on_next = NULL;
+    GRPC_ERROR_UNREF(bs->error);
+    bs->error = error;
+  }
   incoming_byte_stream_unref(exec_ctx, bs);
 }
 
 void grpc_chttp2_incoming_byte_stream_finished(
     grpc_exec_ctx *exec_ctx, grpc_chttp2_incoming_byte_stream *bs,
     grpc_error *error, int from_parsing_thread) {
+  GPR_TIMER_BEGIN("grpc_chttp2_incoming_byte_stream_finished", 0);
   if (from_parsing_thread) {
-    if (error == GRPC_ERROR_NONE) {
-      grpc_chttp2_run_with_global_lock(exec_ctx, bs->transport, bs->stream,
-                                       incoming_byte_stream_finished_ok_locked,
-                                       bs, 0);
-    } else {
-      grpc_chttp2_run_with_global_lock(
-          exec_ctx, bs->transport, bs->stream,
-          incoming_byte_stream_finished_failed_locked,
-          make_bs_fail_args(bs, error), 0);
-    }
+    grpc_closure_init(&bs->finished_action,
+                      incoming_byte_stream_finished_locked, bs);
+    grpc_combiner_execute(exec_ctx, bs->transport->executor.combiner,
+                          &bs->finished_action, GRPC_ERROR_REF(error));
   } else {
-    if (error == GRPC_ERROR_NONE) {
-      incoming_byte_stream_finished_ok_locked(exec_ctx, bs->transport,
-                                              bs->stream, bs);
-    } else {
-      incoming_byte_stream_finished_failed_locked(
-          exec_ctx, bs->transport, bs->stream, make_bs_fail_args(bs, error));
-    }
+    incoming_byte_stream_finished_locked(exec_ctx, bs, error);
   }
+  GPR_TIMER_END("grpc_chttp2_incoming_byte_stream_finished", 0);
 }
 
 grpc_chttp2_incoming_byte_stream *grpc_chttp2_incoming_byte_stream_create(
@@ -2405,6 +2272,7 @@ grpc_chttp2_incoming_byte_stream *grpc_chttp2_incoming_byte_stream_create(
   incoming_byte_stream->base.flags = flags;
   incoming_byte_stream->base.next = incoming_byte_stream_next;
   incoming_byte_stream->base.destroy = incoming_byte_stream_destroy;
+  gpr_mu_init(&incoming_byte_stream->slice_mu);
   gpr_ref_init(&incoming_byte_stream->refs, 2);
   incoming_byte_stream->next_message = NULL;
   incoming_byte_stream->transport = TRANSPORT_FROM_PARSING(transport_parsing);
diff --git a/src/core/ext/transport/chttp2/transport/internal.h b/src/core/ext/transport/chttp2/transport/internal.h
index d67c014e54..04b788b702 100644
--- a/src/core/ext/transport/chttp2/transport/internal.h
+++ b/src/core/ext/transport/chttp2/transport/internal.h
@@ -48,6 +48,7 @@
 #include "src/core/ext/transport/chttp2/transport/hpack_parser.h"
 #include "src/core/ext/transport/chttp2/transport/incoming_metadata.h"
 #include "src/core/ext/transport/chttp2/transport/stream_map.h"
+#include "src/core/lib/iomgr/combiner.h"
 #include "src/core/lib/iomgr/endpoint.h"
 #include "src/core/lib/transport/connectivity_state.h"
 #include "src/core/lib/transport/transport_impl.h"
@@ -161,9 +162,20 @@ struct grpc_chttp2_incoming_byte_stream {
   grpc_chttp2_transport *transport;
   grpc_chttp2_stream *stream;
   int is_tail;
+
+  gpr_mu slice_mu;  // protects slices, on_next
   gpr_slice_buffer slices;
   grpc_closure *on_next;
   gpr_slice *next;
+
+  struct {
+    grpc_closure closure;
+    gpr_slice *slice;
+    size_t max_size_hint;
+    grpc_closure *on_complete;
+  } next_action;
+  grpc_closure destroy_action;
+  grpc_closure finished_action;
 };
 
 typedef struct {
@@ -296,23 +308,11 @@ struct grpc_chttp2_transport_parsing {
   int64_t outgoing_window;
 };
 
-typedef void (*grpc_chttp2_locked_action)(grpc_exec_ctx *ctx,
-                                          grpc_chttp2_transport *t,
-                                          grpc_chttp2_stream *s, void *arg);
-
-typedef struct grpc_chttp2_executor_action_header {
-  grpc_chttp2_stream *stream;
-  grpc_chttp2_locked_action action;
-  struct grpc_chttp2_executor_action_header *next;
-  void *arg;
-} grpc_chttp2_executor_action_header;
-
 typedef enum {
+  /** no writing activity allowed */
+  GRPC_CHTTP2_WRITES_CORKED,
   /** no writing activity */
   GRPC_CHTTP2_WRITING_INACTIVE,
-  /** write has been requested, but not scheduled yet */
-  GRPC_CHTTP2_WRITE_REQUESTED_WITH_POLLER,
-  GRPC_CHTTP2_WRITE_REQUESTED_NO_POLLER,
   /** write has been requested and scheduled against the workqueue */
   GRPC_CHTTP2_WRITE_SCHEDULED,
   /** write has been initiated after being reaped from the workqueue */
@@ -333,7 +333,7 @@ struct grpc_chttp2_transport {
   gpr_refcount shutdown_ep_refs;
 
   struct {
-    gpr_mu mu;
+    grpc_combiner *combiner;
 
     /** is a thread currently in the global lock */
     bool global_active;
@@ -341,9 +341,8 @@ struct grpc_chttp2_transport {
     bool parsing_active;
     /** write execution state of the transport */
     grpc_chttp2_write_state write_state;
-
-    grpc_chttp2_executor_action_header *pending_actions_head;
-    grpc_chttp2_executor_action_header *pending_actions_tail;
+    /** has a check_read_ops been scheduled */
+    bool check_read_ops_scheduled;
   } executor;
 
   /** is the transport destroying itself? */
@@ -380,10 +379,16 @@ struct grpc_chttp2_transport {
   grpc_closure writing_action;
   /** closure to start reading from the endpoint */
   grpc_closure reading_action;
+  grpc_closure reading_action_locked;
+  grpc_closure post_parse_locked;
   /** closure to actually do parsing */
   grpc_closure parsing_action;
   /** closure to initiate writing */
   grpc_closure initiate_writing;
+  /** closure to finish writing */
+  grpc_closure terminate_writing;
+  /** closure to flush read state up the stack */
+  grpc_closure initiate_read_flush_locked;
 
   /** incoming read bytes */
   gpr_slice_buffer read_buffer;
@@ -527,11 +532,16 @@ struct grpc_chttp2_stream_parsing {
 };
 
 struct grpc_chttp2_stream {
+  grpc_chttp2_transport *t;
   grpc_stream_refcount *refcount;
   grpc_chttp2_stream_global global;
   grpc_chttp2_stream_writing writing;
   grpc_chttp2_stream_parsing parsing;
 
+  grpc_closure init_stream;
+  grpc_closure destroy_stream;
+  void *destroy_stream_arg;
+
   grpc_chttp2_stream_link links[STREAM_LIST_COUNT];
   uint8_t included[STREAM_LIST_COUNT];
 };
@@ -626,7 +636,7 @@ int grpc_chttp2_list_pop_waiting_for_concurrency(
     grpc_chttp2_stream_global **stream_global);
 
 void grpc_chttp2_list_add_check_read_ops(
-    grpc_chttp2_transport_global *transport_global,
+    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_global *transport_global,
     grpc_chttp2_stream_global *stream_global);
 bool grpc_chttp2_list_remove_check_read_ops(
     grpc_chttp2_transport_global *transport_global,
@@ -706,12 +716,6 @@ void grpc_chttp2_complete_closure_step(
     grpc_chttp2_stream_global *stream_global, grpc_closure **pclosure,
     grpc_error *error);
 
-void grpc_chttp2_run_with_global_lock(grpc_exec_ctx *exec_ctx,
-                                      grpc_chttp2_transport *transport,
-                                      grpc_chttp2_stream *optional_stream,
-                                      grpc_chttp2_locked_action action,
-                                      void *arg, size_t sizeof_arg);
-
 #define GRPC_CHTTP2_CLIENT_CONNECT_STRING "PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n"
 #define GRPC_CHTTP2_CLIENT_CONNECT_STRLEN \
   (sizeof(GRPC_CHTTP2_CLIENT_CONNECT_STRING) - 1)
diff --git a/src/core/ext/transport/chttp2/transport/parsing.c b/src/core/ext/transport/chttp2/transport/parsing.c
index 482cd55c44..0e6d579ba9 100644
--- a/src/core/ext/transport/chttp2/transport/parsing.c
+++ b/src/core/ext/transport/chttp2/transport/parsing.c
@@ -177,7 +177,8 @@ void grpc_chttp2_publish_reads(
       stream_global->seen_error = true;
       stream_global->exceeded_metadata_size =
           stream_parsing->exceeded_metadata_size;
-      grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
+      grpc_chttp2_list_add_check_read_ops(exec_ctx, transport_global,
+                                          stream_global);
     }
 
     /* flush stats to global stream state */
@@ -203,7 +204,8 @@ void grpc_chttp2_publish_reads(
       stream_global->incoming_frames.tail->is_tail = 0;
     }
     if (stream_parsing->data_parser.incoming_frames.head != NULL) {
-      grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
+      grpc_chttp2_list_add_check_read_ops(exec_ctx, transport_global,
+                                          stream_global);
     }
     grpc_chttp2_incoming_frame_queue_merge(
         &stream_global->incoming_frames,
@@ -219,7 +221,8 @@ void grpc_chttp2_publish_reads(
       GPR_SWAP(grpc_chttp2_incoming_metadata_buffer,
                stream_parsing->metadata_buffer[0],
                stream_global->received_initial_metadata);
-      grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
+      grpc_chttp2_list_add_check_read_ops(exec_ctx, transport_global,
+                                          stream_global);
     }
     if (!stream_global->published_trailing_metadata &&
         stream_parsing->got_metadata_on_parse[1]) {
@@ -228,7 +231,8 @@ void grpc_chttp2_publish_reads(
       GPR_SWAP(grpc_chttp2_incoming_metadata_buffer,
                stream_parsing->metadata_buffer[1],
                stream_global->received_trailing_metadata);
-      grpc_chttp2_list_add_check_read_ops(transport_global, stream_global);
+      grpc_chttp2_list_add_check_read_ops(exec_ctx, transport_global,
+                                          stream_global);
     }
 
     if (stream_parsing->forced_close_error != GRPC_ERROR_NONE) {
diff --git a/src/core/ext/transport/chttp2/transport/stream_lists.c b/src/core/ext/transport/chttp2/transport/stream_lists.c
index 2eb5f5f632..4dc4968248 100644
--- a/src/core/ext/transport/chttp2/transport/stream_lists.c
+++ b/src/core/ext/transport/chttp2/transport/stream_lists.c
@@ -298,8 +298,15 @@ int grpc_chttp2_list_pop_waiting_for_concurrency(
 }
 
 void grpc_chttp2_list_add_check_read_ops(
-    grpc_chttp2_transport_global *transport_global,
+    grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_global *transport_global,
     grpc_chttp2_stream_global *stream_global) {
+  grpc_chttp2_transport *t = TRANSPORT_FROM_GLOBAL(transport_global);
+  if (!t->executor.check_read_ops_scheduled) {
+    grpc_combiner_execute_finally(exec_ctx, t->executor.combiner,
+                                  &t->initiate_read_flush_locked,
+                                  GRPC_ERROR_NONE, false);
+    t->executor.check_read_ops_scheduled = true;
+  }
   stream_list_add(TRANSPORT_FROM_GLOBAL(transport_global),
                   STREAM_FROM_GLOBAL(stream_global),
                   GRPC_CHTTP2_LIST_CHECK_READ_OPS);
diff --git a/src/core/ext/transport/chttp2/transport/writing.c b/src/core/ext/transport/chttp2/transport/writing.c
index 311b26e354..979515bd54 100644
--- a/src/core/ext/transport/chttp2/transport/writing.c
+++ b/src/core/ext/transport/chttp2/transport/writing.c
@@ -55,15 +55,6 @@ int grpc_chttp2_unlocking_check_writes(
       transport_global->settings[GRPC_ACKED_SETTINGS]
                                 [GRPC_CHTTP2_SETTINGS_MAX_FRAME_SIZE];
 
-  /* simple writes are queued to qbuf, and flushed here */
-  gpr_slice_buffer_swap(&transport_global->qbuf, &transport_writing->outbuf);
-  GPR_ASSERT(transport_global->qbuf.count == 0);
-
-  grpc_chttp2_hpack_compressor_set_max_table_size(
-      &transport_writing->hpack_compressor,
-      transport_global->settings[GRPC_PEER_SETTINGS]
-                                [GRPC_CHTTP2_SETTINGS_HEADER_TABLE_SIZE]);
-
   if (transport_global->dirtied_local_settings &&
       !transport_global->sent_local_settings) {
     gpr_slice_buffer_add(
@@ -77,6 +68,16 @@ int grpc_chttp2_unlocking_check_writes(
     transport_global->sent_local_settings = 1;
   }
 
+  /* simple writes are queued to qbuf, and flushed here */
+  gpr_slice_buffer_move_into(&transport_global->qbuf,
+                             &transport_writing->outbuf);
+  GPR_ASSERT(transport_global->qbuf.count == 0);
+
+  grpc_chttp2_hpack_compressor_set_max_table_size(
+      &transport_writing->hpack_compressor,
+      transport_global->settings[GRPC_PEER_SETTINGS]
+                                [GRPC_CHTTP2_SETTINGS_HEADER_TABLE_SIZE]);
+
   GRPC_CHTTP2_FLOW_MOVE_TRANSPORT("write", transport_writing, outgoing_window,
                                   transport_global, outgoing_window);
   if (transport_writing->outgoing_window > 0) {
@@ -344,6 +345,7 @@ static void finalize_outbuf(grpc_exec_ctx *exec_ctx,
 void grpc_chttp2_cleanup_writing(
     grpc_exec_ctx *exec_ctx, grpc_chttp2_transport_global *transport_global,
     grpc_chttp2_transport_writing *transport_writing) {
+  GPR_TIMER_BEGIN("grpc_chttp2_cleanup_writing", 0);
   grpc_chttp2_stream_writing *stream_writing;
   grpc_chttp2_stream_global *stream_global;
 
@@ -382,4 +384,5 @@ void grpc_chttp2_cleanup_writing(
     GRPC_CHTTP2_STREAM_UNREF(exec_ctx, stream_global, "chttp2_writing");
   }
   gpr_slice_buffer_reset_and_unref(&transport_writing->outbuf);
+  GPR_TIMER_END("grpc_chttp2_cleanup_writing", 0);
 }