From 7babe734dcafb5247d7b7798be59536d7eca6e4b Mon Sep 17 00:00:00 2001
From: Ben Turner <bent.mozilla@gmail.com>
Date: Fri, 2 Aug 2013 13:19:36 -0700
Subject: [PATCH] Bug 900711 - '~nsIThreadPool can run the event loop if
 shutdown has not been called'. r=ehsan.

---
 xpcom/threads/nsThreadPool.cpp | 55 +++++++++++++++++++++++++++++++++-
 1 file changed, 54 insertions(+), 1 deletion(-)

diff --git a/xpcom/threads/nsThreadPool.cpp b/xpcom/threads/nsThreadPool.cpp
index 281bd83072a..d7c128a5cc4 100644
--- a/xpcom/threads/nsThreadPool.cpp
+++ b/xpcom/threads/nsThreadPool.cpp
@@ -37,6 +37,24 @@ GetThreadPoolLog()
 #define DEFAULT_IDLE_THREAD_LIMIT 1
 #define DEFAULT_IDLE_THREAD_TIMEOUT PR_SecondsToInterval(60)
 
+class ShutdownHelper MOZ_FINAL : public nsRunnable
+{
+public:
+  NS_DECL_NSIRUNNABLE
+
+  ShutdownHelper(nsCOMArray<nsIThread>& aThreads,
+                 already_AddRefed<nsIThreadPoolListener>& aListener)
+  : mListener(aListener)
+  {
+    MOZ_ASSERT(!aThreads.IsEmpty());
+    mThreads.SwapElements(aThreads);
+  }
+
+private:
+  nsCOMArray<nsIThread> mThreads;
+  nsCOMPtr<nsIThreadPoolListener> mListener;
+};
+
 NS_IMPL_ADDREF(nsThreadPool)
 NS_IMPL_RELEASE(nsThreadPool)
 NS_IMPL_CLASSINFO(nsThreadPool, NULL, nsIClassInfo::THREADSAFE,
@@ -56,7 +74,28 @@ nsThreadPool::nsThreadPool()
 
 nsThreadPool::~nsThreadPool()
 {
-  Shutdown();
+  // Calling Shutdown() directly is not safe since it will spin the event loop
+  // (perhaps during a GC). Instead we try to delay-shutdown each thread that is
+  // still alive.
+  nsCOMArray<nsIThread> threads;
+  nsCOMPtr<nsIThreadPoolListener> listener;
+  {
+    ReentrantMonitorAutoEnter mon(mEvents.GetReentrantMonitor());
+    if (!mShutdown) {
+      NS_WARNING("nsThreadPool destroyed before Shutdown() was called!");
+
+      mThreads.SwapElements(threads);
+      mListener.swap(listener);
+    }
+  }
+
+  if (!threads.IsEmpty()) {
+    nsRefPtr<ShutdownHelper> helper =
+      new ShutdownHelper(threads, listener.forget());
+    if (NS_FAILED(NS_DispatchToMainThread(helper, NS_DISPATCH_NORMAL))) {
+      NS_WARNING("Unable to shut down threads in this thread pool!");
+    }
+  }
 }
 
 nsresult
@@ -374,3 +413,17 @@ nsThreadPool::SetName(const nsACString& aName)
   mName = aName;
   return NS_OK;
 }
+
+NS_IMETHODIMP
+ShutdownHelper::Run()
+{
+  MOZ_ASSERT(!mThreads.IsEmpty());
+
+  for (int32_t i = 0; i < mThreads.Count(); ++i)
+    mThreads[i]->Shutdown();
+
+  mThreads.Clear();
+
+  mListener = nullptr;
+  return NS_OK;
+}