Merge pull request #9963 from jaredpar/fix-8936

Guard against EventListener dispose race

src/InteractiveWindow/EditorTest/InteractiveWindowTest.csproj

@@ -74,6 +74,9 @@
     <Reference Include="WindowsBase" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="..\..\Test\Shared\EventListenerGuard.cs">
+      <Link>EventListenerGuard.cs</Link>
+    </Compile>
     <Compile Include="InteractiveWindowEditorsFactoryService.cs" />
     <Compile Include="InteractiveWindowTestHost.cs" />
     <Compile Include="HistoryTests.cs" />
@@ -98,4 +101,4 @@
     <Import Project="..\..\..\build\Targets\VSL.Imports.targets" />
     <Import Project="..\..\..\build\Targets\Roslyn.Toolsets.Xunit.targets" />
   </ImportGroup>
-</Project>
+</Project>
\ No newline at end of file

src/Test/Shared/EventListenerGuard.cs

+// Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
+
+using Roslyn.Test.Utilities;
+using System;
+using System.Collections.Concurrent;
+using Xunit;
+
+namespace Microsoft.CodeAnalysis.UnitTests
+{
+    public class EventListenerGuard
+    {
+        /// <summary>
+        /// A unit test that guards against the EventListener race condition:
+        ///
+        ///     - https://github.com/dotnet/roslyn/issues/8936
+        ///     - https://github.com/dotnet/corefx/issues/3793
+        ///     
+        /// The underlying issue here is EventListener.DisposeOnShutdown has a race
+        /// condition if a new EventSource is added during an AppDomain or Process 
+        /// exit.  When this occurs there is an unhandled exception during shutdown
+        /// due to a modified collection during enumeration that causes xunit to 
+        /// falsely fail the run. 
+        /// 
+        /// The type CDSCollectionETWBCLProvider triggers this bug in our tests.  It
+        /// is an EventSource for concurrent collections that is loaded on many 
+        /// concurrent collection operations.  These operations are not triggered 
+        /// directly in some of our tests and hence lead to the race.  
+        /// 
+        /// This test guards against them force loading, albeit indirectly, the EventSource 
+        /// instance of CDSCollectionETWBCLProvider.  Hence uses during shutdown 
+        /// are just re-using this instance and don't trigger the race.
+        /// </summary>
+        [WorkItem(8936, "https://github.com/dotnet/roslyn/issues/8936")]
+        [Fact]
+        public void GuardAgainstRace()
+        {
+            // This code will trigger the load of CDSCollectionETWBCLProvider
+            var dictionary = new ConcurrentDictionary<int, int>();
+            dictionary.Clear();
+
+            var log = typeof(ConcurrentDictionary<int, int>)
+                .Assembly
+                .GetType("System.Collections.Concurrent.CDSCollectionETWBCLProvider")
+                .GetField("Log", System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Static)
+                .GetValue(null);
+            Assert.NotNull(log);
+        }
+    }
+}