Bug 886791 - Deadlock can occur if nsThreadPool::Dispatch() is called under lock, r=bsmedberg

xpcom/threads/nsThreadPool.cpp

@@ -100,7 +100,15 @@ nsThreadPool::PutEvent(nsIRunnable *event)
   }
   LOG(("THRD-P(%p) put [%p kill=%d]\n", this, thread.get(), killThread));
   if (killThread) {
-    thread->Shutdown();
+    // Pending events are processed on the current thread during
+    // nsIThread::Shutdown() execution, so if nsThreadPool::Dispatch() is called
+    // under caller's lock then deadlock could occur. This happens e.g. in case
+    // of nsStreamCopier. To prevent this situation, dispatch a shutdown event
+    // to the current thread instead of calling nsIThread::Shutdown() directly.
+
+    nsRefPtr<nsIRunnable> r = NS_NewRunnableMethod(thread,
+                                                   &nsIThread::Shutdown);
+    NS_DispatchToCurrentThread(r);
   } else {
     thread->Dispatch(this, NS_DISPATCH_NORMAL);
   }