Fix QPS Async Client Next loop

test/cpp/qps/client_async.cc

@@ -245,9 +245,20 @@ class AsyncClient : public ClientImpl<StubType, RequestType> {
     if (!cli_cqs_[cq_[thread_idx]]->Next(&got_tag, &ok)) {
       return;
     }
-    ClientRpcContext* ctx;
+    ClientRpcContext* ctx = ClientRpcContext::detag(got_tag);
     std::mutex* shutdown_mu = &shutdown_state_[thread_idx]->mutex;
-    do {
+    shutdown_mu->lock();
+    while (cli_cqs_[cq_[thread_idx]]->DoThenAsyncNext(
+        [&, ctx, ok, entry_ptr, shutdown_mu]() {
+          if (!ctx->RunNextState(ok, entry_ptr)) {
+            // The RPC and callback are done, so clone the ctx
+            // and kickstart the new one
+            ctx->StartNewClone(cli_cqs_[cq_[thread_idx]].get());
+            delete ctx;
+          }
+          shutdown_mu->unlock();
+        },
+        &got_tag, &ok, gpr_inf_future(GPR_CLOCK_REALTIME))) {
       t->UpdateHistogram(entry_ptr);
       // Got a regular event, so process it
       ctx = ClientRpcContext::detag(got_tag);
@@ -265,18 +276,7 @@ class AsyncClient : public ClientImpl<StubType, RequestType> {
         shutdown_mu->unlock();
         return;
       }
-    } while (cli_cqs_[cq_[thread_idx]]->DoThenAsyncNext(
+    }
-        [&, ctx, ok, entry_ptr, shutdown_mu]() {
-          bool next_ok = ok;
-          if (!ctx->RunNextState(next_ok, entry_ptr)) {
-            // The RPC and callback are done, so clone the ctx
-            // and kickstart the new one
-            ctx->StartNewClone(cli_cqs_[cq_[thread_idx]].get());
-            delete ctx;
-          }
-          shutdown_mu->unlock();
-        },
-        &got_tag, &ok, gpr_inf_future(GPR_CLOCK_REALTIME)));
   }
 
   std::vector<std::unique_ptr<CompletionQueue>> cli_cqs_;

test/cpp/qps/server_async.cc

@@ -206,13 +206,12 @@ class AsyncQpsServerTest final : public grpc::testing::Server {
       return;
     }
     ServerRpcContext *ctx;
-    std::mutex *mu_ptr;
+    std::mutex *mu_ptr = &shutdown_state_[thread_idx]->mutex;
     do {
       ctx = detag(got_tag);
       // The tag is a pointer to an RPC context to invoke
       // Proceed while holding a lock to make sure that
       // this thread isn't supposed to shut down
-      mu_ptr = &shutdown_state_[thread_idx]->mutex;
       mu_ptr->lock();
       if (shutdown_state_[thread_idx]->shutdown) {
         mu_ptr->unlock();