fix a race in SF buffer management (0e7f4292) · Commits · e / os / android_frameworks_native

include/private/surfaceflinger/SharedBufferStack.h

+5 −1

Original line number	Diff line number	Diff line
		@@ -151,7 +151,6 @@ public:
		~SharedBufferBase();
		status_t getStatus() const;
		int32_t getIdentity() const;
		size_t getFrontBuffer() const;
		String8 dump(char const* prefix) const;

		protected:
		@@ -226,6 +225,11 @@ private:
		inline ssize_t operator()();
		};

		struct DequeueUpdate : public UpdateBase {
		inline DequeueUpdate(SharedBufferBase* sbb);
		inline ssize_t operator()();
		};

		struct UndoDequeueUpdate : public UpdateBase {
		inline UndoDequeueUpdate(SharedBufferBase* sbb);
		inline ssize_t operator()();

+12 −12

Original line number	Diff line number	Diff line
		@@ -191,12 +191,6 @@ int32_t SharedBufferBase::getIdentity() const
		return stack.identity;
		}

		size_t SharedBufferBase::getFrontBuffer() const
		{
		SharedBufferStack& stack( *mSharedStack );
		return size_t( stack.head );
		}

		String8 SharedBufferBase::dump(char const* prefix) const
		{
		const size_t SIZE = 1024;
		@@ -281,6 +275,16 @@ ssize_t SharedBufferClient::QueueUpdate::operator()() {
		return NO_ERROR;
		}

		SharedBufferClient::DequeueUpdate::DequeueUpdate(SharedBufferBase* sbb)
		: UpdateBase(sbb) {
		}
		ssize_t SharedBufferClient::DequeueUpdate::operator()() {
		if (android_atomic_dec(&stack.available) == 0) {
		LOGW("dequeue probably called from multiple threads!");
		}
		return NO_ERROR;
		}

		SharedBufferClient::UndoDequeueUpdate::UndoDequeueUpdate(SharedBufferBase* sbb)
		: UpdateBase(sbb) {
		}
		@@ -388,12 +392,8 @@ ssize_t SharedBufferClient::dequeue()
		if (err != NO_ERROR)
		return ssize_t(err);

		// NOTE: 'stack.available' is part of the conditions, however
		// decrementing it, never changes any conditions, so we don't need
		// to do this as part of an update.
		if (android_atomic_dec(&stack.available) == 0) {
		LOGW("dequeue probably called from multiple threads!");
		}
		DequeueUpdate update(this);
		updateCondition( update );

		undoDequeueTail = tail;
		int dequeued = stack.index[tail];