From 34d131e70ff1eb7ea049386ebb45e28c13f8656b Mon Sep 17 00:00:00 2001
From: Jan Tattermusch <jtattermusch@google.com>
Date: Tue, 19 May 2020 13:58:36 +0200
Subject: [PATCH] add a repro and fix for #19090

---
 .../Grpc.Core.Tests/CallAfterShutdownTest.cs  | 48 +++++++++++++++++++
 src/csharp/Grpc.Core/Internal/AsyncCall.cs    |  7 ++-
 src/csharp/tests.json                         |  1 +
 3 files changed, 55 insertions(+), 1 deletion(-)
 create mode 100644 src/csharp/Grpc.Core.Tests/CallAfterShutdownTest.cs

diff --git a/src/csharp/Grpc.Core.Tests/CallAfterShutdownTest.cs b/src/csharp/Grpc.Core.Tests/CallAfterShutdownTest.cs
new file mode 100644
index 0000000000000..c1cf7e68ad04d
--- /dev/null
+++ b/src/csharp/Grpc.Core.Tests/CallAfterShutdownTest.cs
@@ -0,0 +1,48 @@
+#region Copyright notice and license
+
+// Copyright 2020 The gRPC Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#endregion
+
+using System;
+using NUnit.Framework;
+
+namespace Grpc.Core.Tests
+{
+    public class CallAfterShutdownTest
+    {
+        Method<string, string> dummyUnaryMethod = new Method<string, string>(MethodType.Unary, "fooservice", "dummyMethod", Marshallers.StringMarshaller, Marshallers.StringMarshaller);
+
+        [Test]
+        public void StartBlockingUnaryCallAfterChannelShutdown()
+        {
+            // create a channel and immediately shut it down.
+            var channel = new Channel("127.0.0.1", 1000, ChannelCredentials.Insecure);
+            channel.ShutdownAsync().Wait();  // also shuts down GrpcEnvironment
+
+            Assert.Throws(typeof(ObjectDisposedException), () => Calls.BlockingUnaryCall(new CallInvocationDetails<string, string>(channel, dummyUnaryMethod, new CallOptions()), "THE REQUEST"));
+        }
+
+        [Test]
+        public void StartAsyncUnaryCallAfterChannelShutdown()
+        {
+            // create a channel and immediately shut it down.
+            var channel = new Channel("127.0.0.1", 1000, ChannelCredentials.Insecure);
+            channel.ShutdownAsync().Wait();  // also shuts down GrpcEnvironment
+
+            Assert.Throws(typeof(ObjectDisposedException), () => Calls.AsyncUnaryCall(new CallInvocationDetails<string, string>(channel, dummyUnaryMethod, new CallOptions()), "THE REQUEST"));
+        }
+    }
+}
diff --git a/src/csharp/Grpc.Core/Internal/AsyncCall.cs b/src/csharp/Grpc.Core/Internal/AsyncCall.cs
index 500842f7c6361..1e570b091de9c 100644
--- a/src/csharp/Grpc.Core/Internal/AsyncCall.cs
+++ b/src/csharp/Grpc.Core/Internal/AsyncCall.cs
@@ -78,7 +78,12 @@ public TResponse UnaryCall(TRequest msg)
             var profiler = Profilers.ForCurrentThread();
 
             using (profiler.NewScope("AsyncCall.UnaryCall"))
-            using (CompletionQueueSafeHandle cq = CompletionQueueSafeHandle.CreateSync())
+
+            // Create a pluckable completion queue for the call. Avoid creating a completion queue when we know the channel has already
+            // been shutdown. In such case, the call will fail with ObjectDisposedException immediately anyway and creating / destroying
+            // a completion queue would lead to crash if this was the last channel in the application (and thus GrpcEnvironment has been shutdown).
+            // See https://github.com/grpc/grpc/issues/19090
+            using (CompletionQueueSafeHandle cq = details.Channel.Handle.IsClosed ?  null : CompletionQueueSafeHandle.CreateSync())
             {
                 bool callStartedOk = false;
                 try
diff --git a/src/csharp/tests.json b/src/csharp/tests.json
index 4b0018e24893f..0ed3a2df61683 100644
--- a/src/csharp/tests.json
+++ b/src/csharp/tests.json
@@ -22,6 +22,7 @@
     "Grpc.Core.Tests.AppDomainUnloadTest",
     "Grpc.Core.Tests.AuthContextTest",
     "Grpc.Core.Tests.AuthPropertyTest",
+    "Grpc.Core.Tests.CallAfterShutdownTest",
     "Grpc.Core.Tests.CallCancellationTest",
     "Grpc.Core.Tests.CallCredentialsTest",
     "Grpc.Core.Tests.CallOptionsTest",