Merge "Fix bug in the way an Event handles a bound thread." into oc-mr1-dev (2b395216) · Commits · e / os / android_hardware_interfaces

neuralnetworks/1.0/vts/functional/Event.cpp

+21 −3

Original line number	Diff line number	Diff line
		@@ -10,9 +10,15 @@ namespace implementation {
		Event::Event() : mStatus(Status::WAITING) {}

		Event::~Event() {
		if (mThread.joinable()) {
		mThread.join();
		}
		// Note that we cannot call Event::join_thread from here: Event is
		// intended to be reference counted, and it is possible that the
		// reference count drops to zero in the bound thread, causing the
		// bound thread to call this destructor. If a thread tries to join
		// itself, it throws an exception, producing a message like the
		// following:
		//
		// terminating with uncaught exception of type std::__1::system_error:
		// thread::join failed: Resource deadlock would occur
		}

		Return<void> Event::notify(ReturnedStatus status) {
		@@ -38,6 +44,7 @@ Event::Status Event::poll() {
		Event::Status Event::wait() {
		std::unique_lock<std::mutex> lock(mMutex);
		mCondition.wait(lock, [this]{return mStatus != Status::WAITING;});
		join_thread_locked();
		return mStatus;
		}

		@@ -69,6 +76,17 @@ bool Event::bind_thread(std::thread&& asyncThread) {
		return true;
		}

		void Event::join_thread() {
		std::lock_guard<std::mutex> lock(mMutex);
		join_thread_locked();
		}

		void Event::join_thread_locked() {
		if (mThread.joinable()) {
		mThread.join();
		}
		}

		} // namespace implementation
		} // namespace V1_0
		} // namespace neuralnetworks

neuralnetworks/1.0/vts/functional/Event.h

+31 −5

Original line number	Diff line number	Diff line
		@@ -139,9 +139,18 @@ struct Event : public IEvent {
		bool on_finish(std::function<bool(void)> callback);

		/**
		* Event::bind_thread binds a thread to the event ensuring that the thread
		* has fully finished and cleaned its resources before the event is
		* destroyed. The thread should be bound using std::move.
		* Event::bind_thread binds a thread to the event for later use by
		* Event::join_thread.
		*
		* The thread must be passed using std::move.
		*
		* Once a thread is bound with Event::bind_thread, the client code
		* should ensure that one of the following occurs before the event is
		* destroyed:
		* - Event::join_thread has been called.
		* - Event::wait has been called.
		* - Event::wait_for has been called and returned other than TIMEOUT.
		* - Event::wait_until has been called and returned other than TIMEOUT.
		*
		* The bound thread shall not call any Event method with the exception of
		* IEvent::notify, which it will call when the thread has finished its
		@@ -156,7 +165,18 @@ struct Event : public IEvent {
		*/
		bool bind_thread(std::thread&& asyncThread);

		/**
		* Event::join_thread ensures that the thread (if any) bound to
		* this event with Event::bind_thread has fully finished and
		* cleaned its resources. It is legal to call this function
		* multiple times, concurrently or sequentially.
		*/
		void join_thread();

		private:
		// Same as Event::join_thread but assumes we already hold a lock on mMutex.
		void join_thread_locked();

		Status mStatus;
		std::mutex mMutex;
		std::condition_variable mCondition;
		@@ -172,6 +192,9 @@ Event::Status Event::wait_for(const std::chrono::duration<Rep,Period>& timeout_d
		std::unique_lock<std::mutex> lock(mMutex);
		std::cv_status status = mCondition.wait_for(lock, timeout_duration,
		[this]{return mStatus != Status::WAITING;});
		if (status != std::cv_status::timeout) {
		join_thread_locked();
		}
		return status != std::cv_status::timeout ? mStatus : Status::TIMEOUT;
		}

		@@ -180,6 +203,9 @@ Event::Status Event::wait_until(const std::chrono::time_point<Clock,Duration>& t
		std::unique_lock<std::mutex> lock(mMutex);
		std::cv_status status = mCondition.wait_until(lock, timeout_time,
		[this]{return mStatus != Status::WAITING;});
		if (status != std::cv_status::timeout) {
		join_thread_locked();
		}
		return status != std::cv_status::timeout ? mStatus : Status::TIMEOUT;
		}