Bug 1510226 - Do not block main thread in nsThread::Init r=froydnj,KrisWright (8c0dd1bc) · Commits · The Tor Project / Applications / Tor Browser

xpcom/threads/ThreadEventTarget.cpp

+3 −1

Original line number	Diff line number	Diff line
		@@ -32,7 +32,9 @@ ThreadEventTarget::ThreadEventTarget(ThreadTargetSink* aSink,
		mThread = PR_GetCurrentThread();
		}

		void ThreadEventTarget::SetCurrentThread() { mThread = PR_GetCurrentThread(); }
		void ThreadEventTarget::SetCurrentThread(PRThread* aThread) {
		mThread = aThread;
		}

		void ThreadEventTarget::ClearCurrentThread() { mThread = nullptr; }

xpcom/threads/ThreadEventTarget.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -30,7 +30,7 @@ class ThreadEventTarget final : public nsISerialEventTarget {

		// Sets the thread for which IsOnCurrentThread returns true to the current
		// thread.
		void SetCurrentThread();
		void SetCurrentThread(PRThread* aThread);
		// Call ClearCurrentThread() before the PRThread is deleted on thread join.
		void ClearCurrentThread();

xpcom/threads/nsThread.cpp

+25 −62

Original line number	Diff line number	Diff line
		@@ -23,6 +23,7 @@
		#include "pratom.h"
		#include "mozilla/BackgroundHangMonitor.h"
		#include "mozilla/CycleCollectedJSContext.h"
		#include "mozilla/DebugOnly.h"
		#include "mozilla/Logging.h"
		#include "nsIObserverService.h"
		#include "mozilla/IOInterposer.h"
		@@ -201,37 +202,6 @@ NS_IMPL_CI_INTERFACE_GETTER(nsThread, nsIThread, nsIThreadInternal,

		//-----------------------------------------------------------------------------

		class nsThreadStartupEvent final : public Runnable {
		public:
		nsThreadStartupEvent()
		: Runnable("nsThreadStartupEvent"),
		mMon("nsThreadStartupEvent.mMon"),
		mInitialized(false) {}

		// This method does not return until the thread startup object is in the
		// completion state.
		void Wait() {
		ReentrantMonitorAutoEnter mon(mMon);
		while (!mInitialized) {
		mon.Wait();
		}
		}

		private:
		~nsThreadStartupEvent() = default;

		NS_IMETHOD Run() override {
		ReentrantMonitorAutoEnter mon(mMon);
		mInitialized = true;
		mon.Notify();
		return NS_OK;
		}

		ReentrantMonitor mMon;
		bool mInitialized;
		};
		//-----------------------------------------------------------------------------

		bool nsThread::ShutdownContextsComp::Equals(
		const ShutdownContexts::elem_type& a,
		const ShutdownContexts::elem_type::Pointer b) const {
		@@ -340,7 +310,7 @@ namespace {

		struct ThreadInitData {
		nsThread* thread;
		const nsACString& name;
		nsCString name;
		};

		} // namespace
		@@ -393,14 +363,16 @@ void nsThread::MaybeRemoveFromThreadList() {
		void nsThread::ThreadFunc(void* aArg) {
		using mozilla::ipc::BackgroundChild;

		ThreadInitData* initData = static_cast<ThreadInitData*>(aArg);
		UniquePtr<ThreadInitData> initData(static_cast<ThreadInitData*>(aArg));
		nsThread* self = initData->thread; // strong reference

		MOZ_ASSERT(self->mEventTarget);
		MOZ_ASSERT(self->mEvents);

		self->mThread = PR_GetCurrentThread();
		self->mEventTarget->SetCurrentThread();
		// Note: see the comment in nsThread::Init, where we set these same values.
		DebugOnly<PRThread*> prev = self->mThread.exchange(PR_GetCurrentThread());
		MOZ_ASSERT(!prev \|\| prev == PR_GetCurrentThread());
		self->mEventTarget->SetCurrentThread(self->mThread);
		SetupCurrentThreadForChaosMode();

		if (!initData->name.IsEmpty()) {
		@@ -424,15 +396,6 @@ void nsThread::ThreadFunc(void* aArg) {
		}
		#endif // MOZ_GECKO_PROFILER

		// Wait for and process startup event
		nsCOMPtr<nsIRunnable> event = self->mEvents->GetEvent(true, nullptr);
		MOZ_ASSERT(event);

		initData = nullptr; // clear before unblocking nsThread::Init

		event->Run(); // unblocks nsThread::Init
		event = nullptr;

		{
		// Scope for MessageLoop.
		MessageLoop loop(MessageLoop::TYPE_MOZILLA_NONMAINTHREAD, self);
		@@ -478,7 +441,8 @@ void nsThread::ThreadFunc(void* aArg) {
		NotNull<nsThreadShutdownContext*> context =
		WrapNotNull(self->mShutdownContext);
		MOZ_ASSERT(context->mTerminatingThread == self);
		event = do_QueryObject(new nsThreadShutdownAckEvent(context));
		nsCOMPtr<nsIRunnable> event =
		do_QueryObject(new nsThreadShutdownAckEvent(context));
		if (context->mIsMainThreadJoining) {
		SchedulerGroup::Dispatch(TaskCategory::Other, event.forget());
		} else {
		@@ -644,35 +608,34 @@ nsThread::~nsThread() {
		nsresult nsThread::Init(const nsACString& aName) {
		MOZ_ASSERT(mEvents);
		MOZ_ASSERT(mEventTarget);

		// spawn thread and wait until it is fully setup
		RefPtr<nsThreadStartupEvent> startup = new nsThreadStartupEvent();
		MOZ_ASSERT(!mThread);

		NS_ADDREF_THIS();

		mShutdownRequired = true;

		ThreadInitData initData = {this, aName};
		UniquePtr<ThreadInitData> initData(
		new ThreadInitData{this, nsCString(aName)});

		PRThread* thread = nullptr;
		// ThreadFunc is responsible for setting mThread
		if (!PR_CreateThread(PR_USER_THREAD, ThreadFunc, &initData,
		PR_PRIORITY_NORMAL, PR_GLOBAL_THREAD, PR_JOINABLE_THREAD,
		mStackSize)) {
		if (!(thread = PR_CreateThread(PR_USER_THREAD, ThreadFunc, initData.get(),
		PR_PRIORITY_NORMAL, PR_GLOBAL_THREAD,
		PR_JOINABLE_THREAD, mStackSize))) {
		NS_RELEASE_THIS();
		return NS_ERROR_OUT_OF_MEMORY;
		}

		// ThreadFunc will wait for this event to be run before it tries to access
		// mThread. By delaying insertion of this event into the queue, we ensure
		// that mThread is set properly.
		{
		mEvents->PutEvent(do_AddRef(startup),
		EventQueuePriority::Normal); // retain a reference
		}
		// The created thread now owns initData, so release our ownership of it.
		Unused << initData.release();

		// Note: we set these both here and inside ThreadFunc, to what should be
		// the same value. This is because calls within ThreadFunc need these values
		// to be set, and our callers need these values to be set.
		DebugOnly<PRThread*> prev = mThread.exchange(thread);
		MOZ_ASSERT(!prev \|\| prev == thread);

		// Wait for thread to call ThreadManager::SetupCurrentThread, which completes
		// initialization of ThreadFunc.
		startup->Wait();
		mEventTarget->SetCurrentThread(thread);
		return NS_OK;
		}