Further

src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver.cc

@@ -132,8 +132,10 @@ static void fd_node_shutdown_locked(fd_node* fdn, const char* reason) {
   }
 }
 
+static void on_timeout(void* arg, grpc_error* error);
 static void on_timeout_locked(void* arg, grpc_error* error);
 
+static void on_ares_backup_poll_alarm(void* arg, grpc_error* error);
 static void on_ares_backup_poll_alarm_locked(void* arg, grpc_error* error);
 
 static void noop_inject_channel_config(ares_channel channel) {}
@@ -173,11 +175,7 @@ grpc_error* grpc_ares_ev_driver_create_locked(grpc_ares_ev_driver** ev_driver,
       grpc_core::NewGrpcPolledFdFactory((*ev_driver)->combiner);
   (*ev_driver)
       ->polled_fd_factory->ConfigureAresChannelLocked((*ev_driver)->channel);
-  GRPC_CLOSURE_INIT(&(*ev_driver)->on_timeout_locked, on_timeout_locked,
-                    *ev_driver, grpc_combiner_scheduler(combiner));
-  GRPC_CLOSURE_INIT(&(*ev_driver)->on_ares_backup_poll_alarm_locked,
-                    on_ares_backup_poll_alarm_locked, *ev_driver,
-                    grpc_combiner_scheduler(combiner));
+
   (*ev_driver)->query_timeout_ms = query_timeout_ms;
   return GRPC_ERROR_NONE;
 }
@@ -235,6 +233,13 @@ static grpc_millis calculate_next_ares_backup_poll_alarm_ms(
          grpc_core::ExecCtx::Get()->Now();
 }
 
+static void on_timeout(void* arg, grpc_error* error) {
+  grpc_ares_ev_driver* driver = static_cast<grpc_ares_ev_driver*>(arg);
+  driver->combiner->Run(GRPC_CLOSURE_INIT(&driver->on_timeout_locked,
+                                          on_timeout_locked, driver, nullptr),
+                        GRPC_ERROR_REF(error));
+}
+
 static void on_timeout_locked(void* arg, grpc_error* error) {
   grpc_ares_ev_driver* driver = static_cast<grpc_ares_ev_driver*>(arg);
   GRPC_CARES_TRACE_LOG(
@@ -247,6 +252,14 @@ static void on_timeout_locked(void* arg, grpc_error* error) {
   grpc_ares_ev_driver_unref(driver);
 }
 
+static void on_ares_backup_poll_alarm(void* arg, grpc_error* error) {
+  grpc_ares_ev_driver* driver = static_cast<grpc_ares_ev_driver*>(arg);
+  driver->combiner->Run(
+      GRPC_CLOSURE_INIT(&driver->on_ares_backup_poll_alarm_locked,
+                        on_ares_backup_poll_alarm_locked, driver, nullptr),
+      GRPC_ERROR_REF(error));
+}
+
 /* In case of non-responsive DNS servers, dropped packets, etc., c-ares has
  * intelligent timeout and retry logic, which we can take advantage of by
  * polling ares_process_fd on time intervals. Overall, the c-ares library is
@@ -279,6 +292,9 @@ static void on_ares_backup_poll_alarm_locked(void* arg, grpc_error* error) {
       grpc_millis next_ares_backup_poll_alarm =
           calculate_next_ares_backup_poll_alarm_ms(driver);
       grpc_ares_ev_driver_ref(driver);
+      GRPC_CLOSURE_INIT(&driver->on_ares_backup_poll_alarm_locked,
+                        on_ares_backup_poll_alarm, driver,
+                        grpc_schedule_on_exec_ctx);
       grpc_timer_init(&driver->ares_backup_poll_alarm,
                       next_ares_backup_poll_alarm,
                       &driver->on_ares_backup_poll_alarm_locked);
@@ -288,6 +304,13 @@ static void on_ares_backup_poll_alarm_locked(void* arg, grpc_error* error) {
   grpc_ares_ev_driver_unref(driver);
 }
 
+static void on_readable(void* arg, grpc_error* error) {
+  fd_node* fdn = static_cast<fd_node*>(arg);
+  fdn->ev_driver->combiner->Run(
+      GRPC_CLOSURE_INIT(&fdn->read_closure, on_readable, fdn, nullptr),
+      GRPC_ERROR_REF(error));
+}
+
 static void on_readable_locked(void* arg, grpc_error* error) {
   fd_node* fdn = static_cast<fd_node*>(arg);
   GPR_ASSERT(fdn->readable_registered);
@@ -313,6 +336,13 @@ static void on_readable_locked(void* arg, grpc_error* error) {
   grpc_ares_ev_driver_unref(ev_driver);
 }
 
+static void on_writable(void* arg, grpc_error* error) {
+  fd_node* fdn = static_cast<fd_node*>(arg);
+  fdn->ev_driver->combiner->Run(
+      GRPC_CLOSURE_INIT(&fdn->write_closure, on_writable, fdn, nullptr),
+      GRPC_ERROR_REF(error));
+}
+
 static void on_writable_locked(void* arg, grpc_error* error) {
   fd_node* fdn = static_cast<fd_node*>(arg);
   GPR_ASSERT(fdn->writable_registered);
@@ -365,10 +395,6 @@ static void grpc_ares_notify_on_event_locked(grpc_ares_ev_driver* ev_driver) {
           fdn->readable_registered = false;
           fdn->writable_registered = false;
           fdn->already_shutdown = false;
-          GRPC_CLOSURE_INIT(&fdn->read_closure, on_readable_locked, fdn,
-                            grpc_combiner_scheduler(ev_driver->combiner));
-          GRPC_CLOSURE_INIT(&fdn->write_closure, on_writable_locked, fdn,
-                            grpc_combiner_scheduler(ev_driver->combiner));
         }
         fdn->next = new_list;
         new_list = fdn;
@@ -380,6 +406,8 @@ static void grpc_ares_notify_on_event_locked(grpc_ares_ev_driver* ev_driver) {
           GRPC_CARES_TRACE_LOG("request:%p notify read on: %s",
                                ev_driver->request,
                                fdn->grpc_polled_fd->GetName());
+          GRPC_CLOSURE_INIT(&fdn->read_closure, on_readable, fdn,
+                            grpc_schedule_on_exec_ctx);
           fdn->grpc_polled_fd->RegisterForOnReadableLocked(&fdn->read_closure);
           fdn->readable_registered = true;
         }
@@ -391,6 +419,8 @@ static void grpc_ares_notify_on_event_locked(grpc_ares_ev_driver* ev_driver) {
                                ev_driver->request,
                                fdn->grpc_polled_fd->GetName());
           grpc_ares_ev_driver_ref(ev_driver);
+          GRPC_CLOSURE_INIT(&fdn->write_closure, on_writable, fdn,
+                            grpc_schedule_on_exec_ctx);
           fdn->grpc_polled_fd->RegisterForOnWriteableLocked(
               &fdn->write_closure);
           fdn->writable_registered = true;
@@ -435,12 +465,17 @@ void grpc_ares_ev_driver_start_locked(grpc_ares_ev_driver* ev_driver) {
         "%" PRId64 " ms",
         ev_driver->request, ev_driver, timeout);
     grpc_ares_ev_driver_ref(ev_driver);
+    GRPC_CLOSURE_INIT(&(*ev_driver)->on_timeout_locked, on_timeout, *ev_driver,
+                      grpc_schedule_on_exec_ctx);
     grpc_timer_init(&ev_driver->query_timeout, timeout,
                     &ev_driver->on_timeout_locked);
     // Initialize the backup poll alarm
     grpc_millis next_ares_backup_poll_alarm =
         calculate_next_ares_backup_poll_alarm_ms(ev_driver);
     grpc_ares_ev_driver_ref(ev_driver);
+    GRPC_CLOSURE_INIT(&ev_driver->on_ares_backup_poll_alarm_locked,
+                      on_ares_backup_poll_alarm, ev_driver,
+                      grpc_schedule_on_exec_ctx);
     grpc_timer_init(&ev_driver->ares_backup_poll_alarm,
                     next_ares_backup_poll_alarm,
                     &ev_driver->on_ares_backup_poll_alarm_locked);

src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver_libuv.cc

@@ -153,9 +153,8 @@ void ares_uv_poll_cb(uv_poll_t* handle, int status, int events) {
   GrpcPolledFdLibuv* polled_fd =
       reinterpret_cast<GrpcPolledFdLibuv*>(handle->data);
   AresUvPollCbArg* arg = New<AresUvPollCbArg>(handle, status, events);
-  GRPC_CLOSURE_SCHED(
-      GRPC_CLOSURE_CREATE(ares_uv_poll_cb_locked, arg,
-                          grpc_combiner_scheduler(polled_fd->combiner_)),
+  polled_fd->combiner_->Run(
+      GRPC_CLOSURE_CREATE(ares_uv_poll_cb_locked, arg, nullptr),
       GRPC_ERROR_NONE);
 }
 

src/core/ext/filters/client_channel/resolver/dns/c_ares/grpc_ares_ev_driver_windows.cc

@@ -110,11 +110,11 @@ class GrpcPolledFdWindows {
     combiner_ = GRPC_COMBINER_REF(combiner, name_);
     GRPC_CLOSURE_INIT(&continue_register_for_on_readable_locked_,
                       &GrpcPolledFdWindows::ContinueRegisterForOnReadableLocked,
-                      this, grpc_combiner_scheduler(combiner_));
+                      this, nullptr);
     GRPC_CLOSURE_INIT(
         &continue_register_for_on_writeable_locked_,
         &GrpcPolledFdWindows::ContinueRegisterForOnWriteableLocked, this,
-        grpc_combiner_scheduler(combiner_));
+        nullptr);
   }
 
   ~GrpcPolledFdWindows() {