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Commit 4d85da4a authored by Pablo Ceballos's avatar Pablo Ceballos
Browse files

BQ: Replace items from back of queue 

It's possible to have one or more non-droppable items in the queue
ahead of a droppable item. In that case we want to replace the
droppable one at the end of the queue. By changing the policy to
always replace the last item in the queue (if it's droppable) we
ensure that there will never be more than one droppable item in the
queue and that it will always be the last one.

Bug 27129258

Change-Id: I9a6234fe12a0095ccb93ceb9cdb74616944900b0
parent 151cc4a9

libs/gui/BufferQueueProducer.cpp

+13 −12
Original line number Diff line number Diff line
@@ -844,30 +844,31 @@ status_t BufferQueueProducer::queueBuffer(int slot, 
            mCore->mQueue.push_back(item);

            frameAvailableListener = mCore->mConsumerListener;

        } else {

            // When the queue is not empty, we need to look at the front buffer

            // state to see if we need to replace it

            BufferQueueCore::Fifo::iterator front(mCore->mQueue.begin());

            if (front->mIsDroppable) {

            // When the queue is not empty, we need to look at the last buffer

            // in the queue to see if we need to replace it

            const BufferItem& last = mCore->mQueue.itemAt(

                    mCore->mQueue.size() - 1);

            if (last.mIsDroppable) {



                if (!front->mIsStale) {

                    mSlots[front->mSlot].mBufferState.freeQueued();

                if (!last.mIsStale) {

                    mSlots[last.mSlot].mBufferState.freeQueued();



                    // After leaving shared buffer mode, the shared buffer will

                    // still be around. Mark it as no longer shared if this

                    // operation causes it to be free.

                    if (!mCore->mSharedBufferMode &&

                            mSlots[front->mSlot].mBufferState.isFree()) {

                        mSlots[front->mSlot].mBufferState.mShared = false;

                            mSlots[last.mSlot].mBufferState.isFree()) {

                        mSlots[last.mSlot].mBufferState.mShared = false;

                    }

                    // Don't put the shared buffer on the free list.

                    if (!mSlots[front->mSlot].mBufferState.isShared()) {

                        mCore->mActiveBuffers.erase(front->mSlot);

                        mCore->mFreeBuffers.push_back(front->mSlot);

                    if (!mSlots[last.mSlot].mBufferState.isShared()) {

                        mCore->mActiveBuffers.erase(last.mSlot);

                        mCore->mFreeBuffers.push_back(last.mSlot);

                    }

                }



                // Overwrite the droppable buffer with the incoming one

                *front = item;

                mCore->mQueue.editItemAt(mCore->mQueue.size() - 1) = item;

                frameReplacedListener = mCore->mConsumerListener;

            } else {

                mCore->mQueue.push_back(item);

services/surfaceflinger/Layer.cpp

+1 −1
Original line number Diff line number Diff line
@@ -251,7 +251,7 @@ void Layer::onFrameReplaced(const BufferItem& item) { 
            ALOGE("Can't replace a frame on an empty queue");

            return;

        }

        mQueueItems.editItemAt(0) = item;

        mQueueItems.editItemAt(mQueueItems.size() - 1) = item;



        // Wake up any pending callbacks

        mLastFrameNumberReceived = item.mFrameNumber;