Avoid the thread jump in server callback APIs.

Add a utility function in iomgr to check whether the caller thread is a
worker for any background poller, and keep grpc combiner from offloading
closures to the default executor if the current thread is a worker for
any background poller.

1 files changed, 6 insertions, 1 deletions

diff --git a/src/core/lib/iomgr/iomgr_posix.cc b/src/core/lib/iomgr/iomgr_posix.cc
index 9386adf060..278c8de688 100644
--- a/src/core/lib/iomgr/iomgr_posix.cc
+++ b/src/core/lib/iomgr/iomgr_posix.cc
@@ -55,9 +55,14 @@ static void iomgr_platform_shutdown_background_closure(void) {
   grpc_shutdown_background_closure();
 }
 
+static bool iomgr_platform_is_any_background_poller_thread(void) {
+  return grpc_is_any_background_poller_thread();
+}
+
 static grpc_iomgr_platform_vtable vtable = {
     iomgr_platform_init, iomgr_platform_flush, iomgr_platform_shutdown,
-    iomgr_platform_shutdown_background_closure};
+    iomgr_platform_shutdown_background_closure,
+    iomgr_platform_is_any_background_poller_thread};
 
 void grpc_set_default_iomgr_platform() {
   grpc_set_tcp_client_impl(&grpc_posix_tcp_client_vtable);