Fix loss of poller bug

src/core/lib/iomgr/ev_epoll1_linux.c

@@ -581,6 +581,7 @@ static bool begin_worker(grpc_pollset *pollset, grpc_pollset_worker *worker,
   }
   worker_insert(pollset, worker);
   if (worker->kick_state == UNKICKED) {
+    GPR_ASSERT(gpr_atm_no_barrier_load(&g_active_poller) != (gpr_atm)worker);
     worker->initialized_cv = true;
     gpr_cv_init(&worker->cv);
     do {
@@ -597,7 +598,7 @@ static bool begin_worker(grpc_pollset *pollset, grpc_pollset_worker *worker,
 }
 
 static bool check_neighbourhood_for_available_poller(
-    pollset_neighbourhood *neighbourhood, grpc_pollset_worker *avoid_worker) {
+    pollset_neighbourhood *neighbourhood) {
   bool found_worker = false;
   do {
     grpc_pollset *inspect = neighbourhood->active_root;
@@ -607,19 +608,24 @@ static bool check_neighbourhood_for_available_poller(
     gpr_mu_lock(&inspect->mu);
     GPR_ASSERT(!inspect->seen_inactive);
     grpc_pollset_worker *inspect_worker = inspect->root_worker;
-    if (inspect_worker == avoid_worker) inspect_worker = inspect_worker->next;
-    if (inspect_worker == avoid_worker) inspect_worker = NULL;
     if (inspect_worker != NULL) {
-      if (gpr_atm_no_barrier_cas(&g_active_poller, 0,
-                                 (gpr_atm)inspect_worker)) {
-        inspect_worker->kick_state = DESIGNATED_POLLER;
-        if (inspect_worker->initialized_cv) {
-          gpr_cv_signal(&inspect_worker->cv);
+      do {
+        if (inspect_worker->kick_state == UNKICKED) {
+          if (gpr_atm_no_barrier_cas(&g_active_poller, 0,
+                                     (gpr_atm)inspect_worker)) {
+            inspect_worker->kick_state = DESIGNATED_POLLER;
+            if (inspect_worker->initialized_cv) {
+              gpr_cv_signal(&inspect_worker->cv);
+            }
+          }
+          // even if we didn't win the cas, there's a worker, we can stop
+          found_worker = true;
+          break;
         }
-      }
-      // even if we didn't win the cas, there's a worker, we can stop
-      found_worker = true;
-    } else {
+        inspect_worker = inspect_worker->next;
+      } while (inspect_worker != inspect->root_worker);
+    }
+    if (!found_worker) {
       inspect->seen_inactive = true;
       move_pollset_to_neighbourhood_list(inspect, &neighbourhood->active_root,
                                          &neighbourhood->inactive_root);
@@ -636,10 +642,10 @@ static void end_worker(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
                        grpc_pollset_worker *worker,
                        grpc_pollset_worker **worker_hdl) {
   if (worker_hdl != NULL) *worker_hdl = NULL;
+  worker->kick_state = KICKED;
   if (gpr_atm_no_barrier_load(&g_active_poller) == (gpr_atm)worker) {
     GPR_ASSERT(!pollset->seen_inactive);
-    GPR_ASSERT(gpr_atm_no_barrier_load(&g_active_poller) == (gpr_atm)worker);
-    if (worker->next != worker) {
+    if (worker->next != worker && worker->next->kick_state == UNKICKED) {
       assert(worker->next->initialized_cv);
       gpr_atm_no_barrier_store(&g_active_poller, (gpr_atm)worker->next);
       worker->next->kick_state = DESIGNATED_POLLER;
@@ -661,7 +667,7 @@ static void end_worker(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
                               g_num_neighbourhoods];
         if (gpr_mu_trylock(&neighbourhood->mu)) {
           found_worker =
-              check_neighbourhood_for_available_poller(neighbourhood, worker);
+              check_neighbourhood_for_available_poller(neighbourhood);
           gpr_mu_unlock(&neighbourhood->mu);
           g_neighbour_scan_state[i] = true;
         } else {
@@ -676,7 +682,7 @@ static void end_worker(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
                                 g_num_neighbourhoods];
           gpr_mu_lock(&neighbourhood->mu);
           found_worker =
-              check_neighbourhood_for_available_poller(neighbourhood, worker);
+              check_neighbourhood_for_available_poller(neighbourhood);
           gpr_mu_unlock(&neighbourhood->mu);
         }
       }
@@ -690,6 +696,7 @@ static void end_worker(grpc_exec_ctx *exec_ctx, grpc_pollset *pollset,
   if (EMPTIED == worker_remove(pollset, worker)) {
     pollset_maybe_finish_shutdown(exec_ctx, pollset);
   }
+  GPR_ASSERT(gpr_atm_no_barrier_load(&g_active_poller) != (gpr_atm)worker);
 }
 
 /* pollset->po.mu lock must be held by the caller before calling this.