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, 4 insertions, 0 deletions

diff --git a/src/core/lib/iomgr/iomgr_internal.cc b/src/core/lib/iomgr/iomgr_internal.cc
index b6c9211865..e68b1cf581 100644
--- a/src/core/lib/iomgr/iomgr_internal.cc
+++ b/src/core/lib/iomgr/iomgr_internal.cc
@@ -45,3 +45,7 @@ void grpc_iomgr_platform_shutdown() { iomgr_platform_vtable->shutdown(); }
 void grpc_iomgr_platform_shutdown_background_closure() {
   iomgr_platform_vtable->shutdown_background_closure();
 }
+
+bool grpc_iomgr_platform_is_any_background_poller_thread() {
+  return iomgr_platform_vtable->is_any_background_poller_thread();
+}