Imported Upstream version 4.3.2.467

Former-commit-id: 9c2cb47f45fa221e661ab616387c9cda183f283d

external/referencesource/mscorlib/system/threading/threadpool.cs

@@ -579,9 +579,7 @@ namespace System.Threading
         // The head and tail of the queue.  We enqueue to the head, and dequeue from the tail.
         internal volatile QueueSegment queueHead;
         internal volatile QueueSegment queueTail;
-#if !FEATURE_CORECLR
         internal bool loggingEnabled;
-#endif
 
         internal static SparseArray<WorkStealingQueue> allThreadQueues = new SparseArray<WorkStealingQueue>(16); //
 
@@ -590,7 +588,7 @@ namespace System.Threading
         public ThreadPoolWorkQueue()
         {
             queueTail = queueHead = new QueueSegment();
-#if !MONO && !FEATURE_CORECLR
+#if !MONO
             loggingEnabled = FrameworkEventSource.Log.IsEnabled(EventLevel.Verbose, FrameworkEventSource.Keywords.ThreadPool|FrameworkEventSource.Keywords.ThreadTransfer);
 #endif
         }
@@ -652,7 +650,7 @@ namespace System.Threading
             if (!forceGlobal)
                 tl = ThreadPoolWorkQueueThreadLocals.threadLocals;
 
-#if !MONO && !FEATURE_CORECLR
+#if !MONO
             if (loggingEnabled)
                 System.Diagnostics.Tracing.FrameworkEventSource.Log.ThreadPoolEnqueueWorkObject(callback);
 #endif
@@ -764,7 +762,7 @@ namespace System.Threading
             //
             workQueue.MarkThreadRequestSatisfied();
 
-#if !MONO && !FEATURE_CORECLR
+#if !MONO
             // Has the desire for logging changed since the last time we entered?
             workQueue.loggingEnabled = FrameworkEventSource.Log.IsEnabled(EventLevel.Verbose, FrameworkEventSource.Keywords.ThreadPool|FrameworkEventSource.Keywords.ThreadTransfer);
 #endif
@@ -826,7 +824,7 @@ namespace System.Threading
                     }
                     else
                     {
-#if !MONO && !FEATURE_CORECLR
+#if !MONO
                         if (workQueue.loggingEnabled)
                             System.Diagnostics.Tracing.FrameworkEventSource.Log.ThreadPoolDequeueWorkObject(workItem);
 #endif
@@ -1190,9 +1188,27 @@ namespace System.Threading
     //
     internal static class _ThreadPoolWaitCallback
     {
+#if FEATURE_INTERCEPTABLE_THREADPOOL_CALLBACK
+        // This feature is used by Xamarin.iOS to use an NSAutoreleasePool
+        // for every task done by the threadpool.
+        static Func<Func<bool>, bool> dispatcher;
+
+        internal static void SetDispatcher (Func<Func<bool>, bool> value)
+        {
+            dispatcher = value;
+        }
+#endif
+
         [System.Security.SecurityCritical]
         static internal bool PerformWaitCallback()
         {
+#if FEATURE_INTERCEPTABLE_THREADPOOL_CALLBACK
+            // store locally first to ensure another thread doesn't clear the field between checking for null and using it.
+            var dispatcher = _ThreadPoolWaitCallback.dispatcher;
+            if (dispatcher != null)
+                return dispatcher (ThreadPoolWorkQueue.Dispatch);
+#endif
+
             return ThreadPoolWorkQueue.Dispatch();
         }
     }