Wait to dispose RequestAborted CTS (#4447)

eng/PatchConfig.props

@@ -33,6 +33,7 @@ Later on, this will be checked using this condition:
       Microsoft.AspNetCore.Http;
       Microsoft.AspNetCore.Mvc.Core;
       Microsoft.AspNetCore.Server.IIS;
+      Microsoft.AspNetCore.Server.Kestrel.Core;
       java:signalr;
     </PackagesInPatch>
   </PropertyGroup>

src/Servers/Kestrel/Core/src/Internal/Http/HttpProtocol.cs

@@ -347,13 +347,10 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
 
             // Lock to prevent CancelRequestAbortedToken from attempting to cancel an disposed CTS.
             lock (_abortLock)
-            {
-                if (!_requestAborted)
             {
                 _abortedCts?.Dispose();
                 _abortedCts = null;
             }
-            }
 
             _requestHeadersParsed = 0;
 
@@ -393,18 +390,19 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
         protected abstract bool TryParseRequest(ReadResult result, out bool endConnection);
 
         private void CancelRequestAbortedToken()
+        {
+            lock (_abortLock)
             {
                 try
                 {
-                _abortedCts.Cancel();
+                    _abortedCts?.Cancel();
-                _abortedCts.Dispose();
-                _abortedCts = null;
                 }
                 catch (Exception ex)
                 {
                     Log.ApplicationError(ConnectionId, TraceIdentifier, ex);
                 }
             }
+        }
 
         protected void AbortRequest()
         {
@@ -416,14 +414,14 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
                 }
 
                 _requestAborted = true;
-            }
 
-            if (_abortedCts != null)
+                if (_abortedCts != null && !_preventRequestAbortedCancellation)
                 {
                     // Potentially calling user code. CancelRequestAbortedToken logs any exceptions.
                     ServiceContext.Scheduler.Schedule(state => ((HttpProtocol)state).CancelRequestAbortedToken(), this);
                 }
             }
+        }
 
         protected void PoisonRequestBodyStream(Exception abortReason)
         {
@@ -441,8 +439,6 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http
                 }
 
                 _preventRequestAbortedCancellation = true;
-                _abortedCts?.Dispose();
-                _abortedCts = null;
             }
         }
 

src/Servers/Kestrel/Core/test/Http1ConnectionTests.cs

@@ -53,7 +53,11 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
             var connectionFeatures = new FeatureCollection();
             connectionFeatures.Set(Mock.Of<IConnectionLifetimeFeature>());
 
-            _serviceContext = new TestServiceContext();
+            _serviceContext = new TestServiceContext()
+            {
+                Scheduler = PipeScheduler.Inline
+            };
+
             _timeoutControl = new Mock<ITimeoutControl>();
             _http1ConnectionContext = new HttpConnectionContext
             {
@@ -724,6 +728,25 @@ namespace Microsoft.AspNetCore.Server.Kestrel.Core.Tests
             Assert.False(_http1Connection.RequestAborted.IsCancellationRequested);
         }
 
+        [Fact]
+        public void RequestAbortedTokenIsFullyUsableAfterCancellation()
+        {
+            var originalToken = _http1Connection.RequestAborted;
+            var originalRegistration = originalToken.Register(() => { });
+
+            _http1Connection.Abort(new ConnectionAbortedException());
+
+            Assert.True(originalToken.WaitHandle.WaitOne(TestConstants.DefaultTimeout));
+            Assert.True(_http1Connection.RequestAborted.WaitHandle.WaitOne(TestConstants.DefaultTimeout));
+
+#if NETCOREAPP2_2
+            Assert.Equal(originalToken, originalRegistration.Token);
+#elif NET461
+#else
+#error Target framework needs to be updated
+#endif
+        }
+
         [Fact]
         public async Task ExceptionDetailNotIncludedWhenLogLevelInformationNotEnabled()
         {