fix: avoid doing a poll when already shutdown

src/core/lib/iomgr/ev_epollex_linux.cc

@@ -199,6 +199,7 @@ struct grpc_pollset {
   pollable* active_pollable;
   bool kicked_without_poller;
   grpc_closure* shutdown_closure;
+  bool already_shutdown;
   grpc_pollset_worker* root_worker;
   int containing_pollset_set_count;
 };
@@ -562,6 +563,7 @@ static void pollset_maybe_finish_shutdown(grpc_pollset* pollset) {
       pollset->containing_pollset_set_count == 0) {
     GRPC_CLOSURE_SCHED(pollset->shutdown_closure, GRPC_ERROR_NONE);
     pollset->shutdown_closure = nullptr;
+    pollset->already_shutdown = true;
   }
 }
 
@@ -862,7 +864,8 @@ static worker_remove_result worker_remove(grpc_pollset_worker** root_worker,
 static bool begin_worker(grpc_pollset* pollset, grpc_pollset_worker* worker,
                          grpc_pollset_worker** worker_hdl,
                          grpc_millis deadline) {
-  bool do_poll = (pollset->shutdown_closure == nullptr);
+  bool do_poll =
+      (pollset->shutdown_closure == nullptr && !pollset->already_shutdown);
   if (worker_hdl != nullptr) *worker_hdl = worker;
   worker->initialized_cv = false;
   worker->kicked = false;