Fix for synchronous cancellation bug https://bugzilla.xamarin.com/sho…

…w_bug.cgi?id=4173
mgranell · Apr 3, 2012 · 87ad22d · 87ad22d
1 parent 1b09033
commit 87ad22d
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Showing 2 changed files with 35 additions and 25 deletions.
diff --git a/mcs/class/corlib/System.Threading/CancellationTokenSource.cs b/mcs/class/corlib/System.Threading/CancellationTokenSource.cs
@@ -126,26 +126,44 @@ public void Cancel (bool throwOnFirstException)
 
 			List<Exception> exceptions = null;
 
+			// Allow callbacks to be removed during the processing
+			// of the set of callbacks.
+			CancellationTokenRegistration[] localCallbacks;
 			lock (syncRoot) {
-				try {
-					foreach (var item in callbacks) {
-						if (throwOnFirstException) {
-							item.Value ();
-						} else {
-							try {
-								item.Value ();
-							} catch (Exception e) {
-								if (exceptions == null)
-									exceptions = new List<Exception> ();
+				 localCallbacks = new CancellationTokenRegistration[callbacks.Count];
+				 callbacks.Keys.CopyTo(localCallbacks, 0);
+			}
+										
+			try {
+				foreach (var registration in localCallbacks) {
+					Action callback;
+					lock (syncRoot) {
+						callbacks.TryGetValue(registration, out callback);
+					}
 
-								exceptions.Add (e);
-							}
+					if (callback == null) {
+							continue;
+					}
+
+					if (throwOnFirstException) {
+						callback ();
+					} else {
+						try {
+							callback ();
+						} catch (Exception e) {
+							if (exceptions == null)
+								exceptions = new List<Exception> ();
+
+							exceptions.Add (e);
 						}
 					}
-				} finally {
-					callbacks.Clear ();
 				}
 			}
+			finally {
+				lock (syncRoot) {
+				 callbacks.Clear();
+				}				
+			}
 
 			Thread.MemoryBarrier ();
 			processed = true;
@@ -265,19 +283,11 @@ internal CancellationTokenRegistration Register (Action callback, bool useSynchr
 
 		internal void RemoveCallback (CancellationTokenRegistration tokenReg)
 		{
-			if (!canceled) {
+			if (!processed) {
 				lock (syncRoot) {
-					if (!canceled) {
-						callbacks.Remove (tokenReg);
-						return;
-					}
+					callbacks.Remove (tokenReg);
 				}
 			}
-
-			SpinWait sw = new SpinWait ();
-			while (!processed)
-				sw.SpinOnce ();
-
 		}
 	}
 }

diff --git a/mcs/class/corlib/corlib_test.dll.sources b/mcs/class/corlib/corlib_test.dll.sources
@@ -468,4 +468,4 @@ System.Threading/CountdownEventTests.cs
 System/AggregateExceptionTests.cs
 System.Threading/ThreadLocalTests.cs
 System.Threading/SpinLockTests.cs
-
+System.Threading.Tasks/TaskCancellationTest.cs