Bug 1204784: Do not shut the main thread down before all outstanding asynchronous thread shutdowns complete. r=froydnj

--HG--
extra : rebase_source : 9f4c8a219e2fa6dfbfec78f9f390726f2f07f683

xpcom/threads/nsThread.cpp

@@ -403,6 +403,9 @@ nsThread::ThreadFunc(void* aArg)
     BackgroundChild::CloseForCurrentThread();
 #endif // defined(MOZILLA_XPCOMRT_API)
 
+    // NB: The main thread does not shut down here!  It shuts down via
+    // nsThreadManager::Shutdown.
+
     // Do NS_ProcessPendingEvents but with special handling to set
     // mEventsAreDoomed atomically with the removal of the last event. The key
     // invariant here is that we will never permit PutEvent to succeed if the
@@ -411,10 +414,7 @@ nsThread::ThreadFunc(void* aArg)
     // as we have outstanding mRequestedShutdownContexts.
     while (true) {
       // Check and see if we're waiting on any threads.
-      while (self->mRequestedShutdownContexts.Length()) {
-        // We can't stop accepting events just yet.  Block and check again.
-        NS_ProcessNextEvent(self, true);
-      }
+      self->WaitForAllAsynchronousShutdowns();
 
       {
         MutexAutoLock lock(self->mLock);
@@ -778,6 +778,14 @@ nsThread::ShutdownComplete(nsThreadShutdownContext* aContext)
     aContext->joiningThread->mRequestedShutdownContexts.RemoveElement(aContext));
 }
 
+void
+nsThread::WaitForAllAsynchronousShutdowns()
+{
+  while (mRequestedShutdownContexts.Length()) {
+    NS_ProcessNextEvent(this, true);
+  }
+}
+
 NS_IMETHODIMP
 nsThread::Shutdown()
 {

xpcom/threads/nsThread.h

@@ -76,6 +76,8 @@ public:
 
   void ShutdownComplete(struct nsThreadShutdownContext* aContext);
 
+  void WaitForAllAsynchronousShutdowns();
+
 protected:
   class nsChainedEventQueue;
 

xpcom/threads/nsThreadManager.cpp

@@ -155,6 +155,12 @@ nsThreadManager::Shutdown()
     }
   }
 
+  // NB: It's possible that there are events in the queue that want to *start*
+  // an asynchronous shutdown. But we have already shutdown the threads above,
+  // so there's no need to worry about them. We only have to wait for all
+  // in-flight asynchronous thread shutdowns to complete.
+  mMainThread->WaitForAllAsynchronousShutdowns();
+
   // In case there are any more events somehow...
   NS_ProcessPendingEvents(mMainThread);