Add synchronization so startup completes before shutdown begins

src/core/lib/surface/server.c

@@ -212,6 +212,11 @@ struct grpc_server {
   gpr_mu mu_global; /* mutex for server and channel state */
   gpr_mu mu_call;   /* mutex for call-specific state */
 
+  /* startup synchronization: flag is protected by mu_global, signals whether
+     we are doing the listener start routine or not */
+  bool starting;
+  gpr_cv starting_cv;
+
   registered_method *registered_methods;
   /** one request matcher for unregistered methods */
   request_matcher unregistered_request_matcher;
@@ -389,6 +394,7 @@ static void server_delete(grpc_exec_ctx *exec_ctx, grpc_server *server) {
   grpc_channel_args_destroy(exec_ctx, server->channel_args);
   gpr_mu_destroy(&server->mu_global);
   gpr_mu_destroy(&server->mu_call);
+  gpr_cv_destroy(&server->starting_cv);
   while ((rm = server->registered_methods) != NULL) {
     server->registered_methods = rm->next;
     if (server->started) {
@@ -1022,6 +1028,7 @@ grpc_server *grpc_server_create(const grpc_channel_args *args, void *reserved) {
 
   gpr_mu_init(&server->mu_global);
   gpr_mu_init(&server->mu_call);
+  gpr_cv_init(&server->starting_cv);
 
   /* decremented by grpc_server_destroy */
   gpr_ref_init(&server->internal_refcount, 1);
@@ -1084,6 +1091,12 @@ static void start_listeners(grpc_exec_ctx *exec_ctx, void *s,
   for (listener *l = server->listeners; l; l = l->next) {
     l->start(exec_ctx, server, l->arg, server->pollsets, server->pollset_count);
   }
+
+  gpr_mu_lock(&server->mu_global);
+  server->starting = false;
+  gpr_cv_signal(&server->starting_cv);
+  gpr_mu_unlock(&server->mu_global);
+
   server_unref(exec_ctx, server);
 }
 
@@ -1122,6 +1135,7 @@ void grpc_server_start(grpc_server *server) {
   }
 
   server_ref(server);
+  server->starting = true;
   grpc_closure_sched(&exec_ctx, grpc_closure_create(start_listeners, server,
                                                     grpc_executor_scheduler),
                      GRPC_ERROR_NONE);
@@ -1258,8 +1272,14 @@ void grpc_server_shutdown_and_notify(grpc_server *server,
   GRPC_API_TRACE("grpc_server_shutdown_and_notify(server=%p, cq=%p, tag=%p)", 3,
                  (server, cq, tag));
 
-  /* lock, and gather up some stuff to do */
+  /* wait for startup to be finished: locks mu_global */
   gpr_mu_lock(&server->mu_global);
+  while (server->starting) {
+    gpr_cv_wait(&server->starting_cv, &server->mu_global,
+                gpr_inf_future(GPR_CLOCK_REALTIME));
+  }
+
+  /* stay locked, and gather up some stuff to do */
   grpc_cq_begin_op(cq, tag);
   if (server->shutdown_published) {
     grpc_cq_end_op(&exec_ctx, cq, tag, GRPC_ERROR_NONE, done_published_shutdown,