Bug 953435 - Browser hang on Mac if an AfterProcessNextEvent callback tries to spin the event loop, r=nfroyd+smichaud

--HG--
extra : rebase_source : e999d852f5f73b18f37ff6a5488cc171c95d9e61

widget/cocoa/nsAppShell.h

@@ -109,7 +109,6 @@ protected:
   // to 3%-4%).  See bmo bug 395397.
   static const uint32_t  kHadMoreEventsCountMax = 3;
 
-  int32_t            mRecursionDepth;
   int32_t            mNativeEventCallbackDepth;
   // Can be set from different threads, so must be modified atomically
   int32_t            mNativeEventScheduledDepth;

widget/cocoa/nsAppShell.mm

@@ -210,7 +210,6 @@ nsAppShell::nsAppShell()
 , mTerminated(false)
 , mSkippedNativeCallback(false)
 , mHadMoreEventsCount(0)
-, mRecursionDepth(0)
 , mNativeEventCallbackDepth(0)
 , mNativeEventScheduledDepth(0)
 {
@@ -712,11 +711,14 @@ nsAppShell::ProcessNextNativeEvent(bool aMayWait)
 bool
 nsAppShell::InGeckoMainEventLoop()
 {
-  if ((gXULModalLevel > 0) || (mRecursionDepth > 0))
+  if (gXULModalLevel > 0)
     return false;
   if (mNativeEventCallbackDepth <= 0)
     return false;
-  return true;
+
+  bool isProcessingEvents = false;
+  NS_GetCurrentThread()->GetIsProcessingEvents(&isProcessingEvents);
+  return !isProcessingEvents;
 }
 
 // Run
@@ -818,8 +820,6 @@ nsAppShell::OnProcessNextEvent(nsIThreadInternal *aThread, bool aMayWait,
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NSRESULT;
 
-  mRecursionDepth = aRecursionDepth;
-
   NS_ASSERTION(mAutoreleasePools,
                "No stack on which to store autorelease pool");
 
@@ -845,8 +845,6 @@ nsAppShell::AfterProcessNextEvent(nsIThreadInternal *aThread,
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NSRESULT;
 
-  mRecursionDepth = aRecursionDepth;
-
   CFIndex count = ::CFArrayGetCount(mAutoreleasePools);
 
   NS_ASSERTION(mAutoreleasePools && count,

xpcom/threads/LazyIdleThread.cpp

@@ -462,6 +462,17 @@ LazyIdleThread::ProcessNextEvent(bool aMayWait,
   return NS_ERROR_UNEXPECTED;
 }
 
+NS_IMETHODIMP
+LazyIdleThread::GetIsProcessingEvents(bool* aIsProcessing)
+{
+  if (mThread) {
+    return mThread->GetIsProcessingEvents(aIsProcessing);
+  }
+
+  *aIsProcessing = false;
+  return NS_OK;
+}
+
 NS_IMETHODIMP
 LazyIdleThread::Notify(nsITimer* aTimer)
 {

xpcom/threads/nsIThread.idl

@@ -17,7 +17,7 @@
  *
  * See nsIThreadManager for the API used to create and locate threads.
  */
-[scriptable, uuid(9c889946-a73a-4af3-ae9a-ea64f7d4e3ca)]
+[scriptable, uuid(4df07d3a-e759-4256-ba4e-7e2265354ec3)]
 interface nsIThread : nsIEventTarget
 {
   /**
@@ -82,4 +82,10 @@ interface nsIThread : nsIEventTarget
    *   not the current thread.
    */
   boolean processNextEvent(in boolean mayWait);
+
+  /**
+   * true if we're processing runnables or thread observers and if this is the
+   * current thread.
+   */
+  readonly attribute boolean isProcessingEvents;
 };

xpcom/threads/nsThread.cpp

@@ -304,6 +304,7 @@ nsThread::nsThread(MainThreadFlag aMainThread, uint32_t aStackSize)
   , mThread(nullptr)
   , mRunningEvent(0)
   , mStackSize(aStackSize)
+  , mProcessingEvent(0)
   , mShutdownContext(nullptr)
   , mShutdownRequired(false)
   , mEventsAreDoomed(false)
@@ -596,6 +597,8 @@ nsThread::ProcessNextEvent(bool mayWait, bool *result)
     }
   }
 
+  ++mProcessingEvent;
+
   bool notifyMainThreadObserver =
     (MAIN_THREAD == mIsMainThread) && sMainThreadObserver;
   if (notifyMainThreadObserver) 
@@ -650,9 +653,22 @@ nsThread::ProcessNextEvent(bool mayWait, bool *result)
   if (notifyMainThreadObserver && sMainThreadObserver)
     sMainThreadObserver->AfterProcessNextEvent(this, mRunningEvent, *result);
 
+  --mProcessingEvent;
+
   return rv;
 }
 
+NS_IMETHODIMP
+nsThread::GetIsProcessingEvents(bool* aIsProcessing)
+{
+  if (NS_WARN_IF(PR_GetCurrentThread() != mThread)) {
+    return NS_ERROR_NOT_SAME_THREAD;
+  }
+
+  *aIsProcessing = mProcessingEvent != 0;
+  return NS_OK;
+}
+
 //-----------------------------------------------------------------------------
 // nsISupportsPriority
 

xpcom/threads/nsThread.h

@@ -150,6 +150,8 @@ protected:
   uint32_t  mRunningEvent;  // counter
   uint32_t  mStackSize;
 
+  uint32_t  mProcessingEvent;
+
   struct nsThreadShutdownContext *mShutdownContext;
 
   bool mShutdownRequired;