make sure to update the tail pointer when undoing a dequeue (c7d56010) · Commits · e / os / android_frameworks_native-old

include/private/ui/SharedBufferStack.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -229,6 +229,8 @@ private:
		friend struct DequeueCondition;
		friend struct LockCondition;

		int32_t computeTail() const;

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

+15 −5

Original line number	Diff line number	Diff line
		@@ -245,20 +245,27 @@ ssize_t SharedBufferServer::StatusUpdate::operator()() {
		SharedBufferClient::SharedBufferClient(SharedClient* sharedClient,
		int surface, int num)
		: SharedBufferBase(sharedClient, surface, num), tail(0)
		{
		tail = computeTail();
		}

		int32_t SharedBufferClient::computeTail() const
		{
		SharedBufferStack& stack( *mSharedStack );
		int32_t avail;
		int32_t head;
		// we need to make sure we read available and head coherently,
		// w.r.t RetireUpdate.
		int32_t newTail;
		int32_t avail;
		int32_t head;
		do {
		avail = stack.available;
		head = stack.head;
		} while (stack.available != avail);
		tail = head - avail + 1;
		if (tail < 0) {
		tail += num;
		newTail = head - avail + 1;
		if (newTail < 0) {
		newTail += mNumBuffers;
		}
		return newTail;
		}

		ssize_t SharedBufferClient::dequeue()
		@@ -296,6 +303,9 @@ status_t SharedBufferClient::undoDequeue(int buf)
		{
		UndoDequeueUpdate update(this);
		status_t err = updateCondition( update );
		if (err == NO_ERROR) {
		tail = computeTail();
		}
		return err;
		}