Merge github.com:grpc/grpc into delayed-write

src/core/lib/iomgr/tcp_server_posix.c

@@ -134,7 +134,7 @@ struct grpc_tcp_server {
   size_t pollset_count;
 
   /* next pollset to assign a channel to */
-  size_t next_pollset_to_assign;
+  gpr_atm next_pollset_to_assign;
 };
 
 static gpr_once check_init = GPR_ONCE_INIT;
@@ -181,7 +181,7 @@ grpc_error *grpc_tcp_server_create(grpc_closure *shutdown_complete,
   s->head = NULL;
   s->tail = NULL;
   s->nports = 0;
-  s->next_pollset_to_assign = 0;
+  gpr_atm_no_barrier_store(&s->next_pollset_to_assign, 0);
   *server = s;
   return GRPC_ERROR_NONE;
 }
@@ -369,7 +369,8 @@ static void on_read(grpc_exec_ctx *exec_ctx, void *arg, grpc_error *err) {
   }
 
   read_notifier_pollset =
-      sp->server->pollsets[(sp->server->next_pollset_to_assign++) %
+      sp->server->pollsets[(size_t)gpr_atm_no_barrier_fetch_add(
+                               &sp->server->next_pollset_to_assign, 1) %
                            sp->server->pollset_count];
 
   /* loop until accept4 returns EAGAIN, and then re-arm notification */