Make sure that nothing gets added to cq after shutdown

test/cpp/qps/server_async.cc

@@ -33,6 +33,7 @@
 
 #include <forward_list>
 #include <functional>
+#include <mutex>
 #include <sys/time.h>
 #include <sys/resource.h>
 #include <sys/signal.h>
@@ -64,7 +65,8 @@ namespace testing {
 class AsyncQpsServerTest : public Server {
  public:
   AsyncQpsServerTest(const ServerConfig &config, int port)
-      : srv_cq_(), async_service_(&srv_cq_), server_(nullptr) {
+      : srv_cq_(), async_service_(&srv_cq_), server_(nullptr),
+        shutdown_(false) {
     char *server_address = NULL;
     gpr_join_host_port(&server_address, "::", port);
 
@@ -100,6 +102,8 @@ class AsyncQpsServerTest : public Server {
 	  // The tag is a pointer to an RPC context to invoke
 	  if (ctx->RunNextState(ok) == false) {
 	    // this RPC context is done, so refresh it
+            std::lock_guard<std::mutex> g(shutdown_mutex_);
+            if (!shutdown_)
               ctx->Reset();
 	  }
         }
@@ -109,7 +113,11 @@ class AsyncQpsServerTest : public Server {
   }
   ~AsyncQpsServerTest() {
     server_->Shutdown();
+    {
+      std::lock_guard<std::mutex> g(shutdown_mutex_);
+      shutdown_ = true;
       srv_cq_.Shutdown();
+    }
     for (auto &thr : threads_) {
       thr.join();
     }
@@ -291,6 +299,9 @@ class AsyncQpsServerTest : public Server {
 		     SimpleResponse,SimpleRequest> *, void *)>
       request_streaming_;
   std::forward_list<ServerRpcContext *> contexts_;
+
+  std::mutex shutdown_mutex_;
+  bool shutdown_;
 };
 
 std::unique_ptr<Server> CreateAsyncServer(const ServerConfig &config,