Bug 1236789. Avoid creating an unnecessary thread pool thread for... (d6063164) · Commits · clairehurst / Tor Browser

xpcom/threads/SharedThreadPool.h

+5 −0

Original line number	Diff line number	Diff line
		@@ -55,6 +55,11 @@ public:
		// Forward behaviour to wrapped thread pool implementation.
		NS_FORWARD_SAFE_NSITHREADPOOL(mPool);

		// Call this when dispatching from an event on the same
		// threadpool that is about to complete. We should not create a new thread
		// in that case since a thread is about to become idle.
		nsresult TailDispatch(nsIRunnable *event) { return Dispatch(event, NS_DISPATCH_TAIL); }

		NS_IMETHOD DispatchFromScript(nsIRunnable *event, uint32_t flags) override {
		return Dispatch(event, flags);
		}

+1 −1

Original line number	Diff line number	Diff line
		@@ -193,7 +193,7 @@ TaskQueue::Runner::Run()
		// run in a loop here so that we don't hog the thread pool. This means we may
		// run on another thread next time, but we rely on the memory fences from
		// mQueueMonitor for thread safety of non-threadsafe tasks.
		nsresult rv = mQueue->mPool->Dispatch(this, NS_DISPATCH_NORMAL);
		nsresult rv = mQueue->mPool->TailDispatch(this);
		if (NS_FAILED(rv)) {
		// Failed to dispatch, shutdown!
		MonitorAutoLock mon(mQueue->mQueueMonitor);

+13 −0

Original line number	Diff line number	Diff line
		@@ -40,6 +40,18 @@ interface nsIEventTarget : nsISupports
		*/
		const unsigned long DISPATCH_SYNC = 1;

		/**
		* This flag specifies that the dispatch is occurring from a running event
		* that was dispatched to the same event target, and that event is about to
		* finish.
		*
		* A thread pool can use this as an optimization hint to not spin up
		* another thread, since the current thread is about to become idle.
		*
		* These events are always async.
		*/
		const unsigned long DISPATCH_TAIL = 2;

		/**
		* Check to see if this event target is associated with the current thread.
		*
		@@ -91,4 +103,5 @@ interface nsIEventTarget : nsISupports
		// convenient aliases:
		#define NS_DISPATCH_NORMAL nsIEventTarget::DISPATCH_NORMAL
		#define NS_DISPATCH_SYNC nsIEventTarget::DISPATCH_SYNC
		#define NS_DISPATCH_TAIL nsIEventTarget::DISPATCH_TAIL
		%}

+4 −3

Original line number	Diff line number	Diff line
		@@ -64,11 +64,11 @@ nsresult
		nsThreadPool::PutEvent(nsIRunnable* aEvent)
		{
		nsCOMPtr<nsIRunnable> event(aEvent);
		return PutEvent(event.forget());
		return PutEvent(event.forget(), 0);
		}

		nsresult
		nsThreadPool::PutEvent(already_AddRefed<nsIRunnable>&& aEvent)
		nsThreadPool::PutEvent(already_AddRefed<nsIRunnable>&& aEvent, uint32_t aFlags)
		{
		// Avoid spawning a new thread while holding the event queue lock...

		@@ -86,6 +86,7 @@ nsThreadPool::PutEvent(already_AddRefed<nsIRunnable>&& aEvent)

		// Make sure we have a thread to service this event.
		if (mThreads.Count() < (int32_t)mThreadLimit &&
		!(aFlags & NS_DISPATCH_TAIL) &&
		// Spawn a new thread if we don't have enough idle threads to serve
		// pending events immediately.
		mEvents.Count(lock) >= mIdleCount) {
		@@ -272,7 +273,7 @@ nsThreadPool::Dispatch(already_AddRefed<nsIRunnable>&& aEvent, uint32_t aFlags)
		}
		} else {
		NS_ASSERTION(aFlags == NS_DISPATCH_NORMAL, "unexpected dispatch flags");
		PutEvent(Move(aEvent));
		PutEvent(Move(aEvent), aFlags);
		}
		return NS_OK;
		}

+1 −1

Original line number	Diff line number	Diff line
		@@ -37,7 +37,7 @@ private:

		void ShutdownThread(nsIThread* aThread);
		nsresult PutEvent(nsIRunnable* aEvent);
		nsresult PutEvent(already_AddRefed<nsIRunnable>&& aEvent);
		nsresult PutEvent(already_AddRefed<nsIRunnable>&& aEvent, uint32_t aFlags);

		nsCOMArray<nsIThread> mThreads;
		mozilla::Mutex mMutex;