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, 1 insertions, 0 deletions

diff --git a/test/cpp/microbenchmarks/bm_cq_multiple_threads.cc b/test/cpp/microbenchmarks/bm_cq_multiple_threads.cc
index dca97c85b1..7aa197b597 100644
--- a/test/cpp/microbenchmarks/bm_cq_multiple_threads.cc
+++ b/test/cpp/microbenchmarks/bm_cq_multiple_threads.cc
@@ -94,6 +94,7 @@ static const grpc_event_engine_vtable* init_engine_vtable(bool) {
   g_vtable.pollset_destroy = pollset_destroy;
   g_vtable.pollset_work = pollset_work;
   g_vtable.pollset_kick = pollset_kick;
+  g_vtable.is_any_background_poller_thread = [] { return false; };
   g_vtable.shutdown_background_closure = [] {};
   g_vtable.shutdown_engine = [] {};