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, 3 insertions, 0 deletions

diff --git a/src/core/lib/iomgr/ev_poll_posix.cc b/src/core/lib/iomgr/ev_poll_posix.cc
index 67cbfbbd02..c479206410 100644
--- a/src/core/lib/iomgr/ev_poll_posix.cc
+++ b/src/core/lib/iomgr/ev_poll_posix.cc
@@ -1782,6 +1782,8 @@ static void global_cv_fd_table_shutdown() {
  * event engine binding
  */
 
+static bool is_any_background_poller_thread(void) { return false; }
+
 static void shutdown_background_closure(void) {}
 
 static void shutdown_engine(void) {
@@ -1828,6 +1830,7 @@ static const grpc_event_engine_vtable vtable = {
     pollset_set_add_fd,
     pollset_set_del_fd,
 
+    is_any_background_poller_thread,
     shutdown_background_closure,
     shutdown_engine,
 };