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Commit fe95fd7e authored by Ady Abraham's avatar Ady Abraham
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SurfaceFlinger: check fence when acquiring buffer with PTS 

This is a fix for a condition where SurfaceFlinger may pass
a buffer to HWC before the fence was signaled. This can happen when
presentation timestamp is set and the buffer behind the front of
the queue has current timestamp.

Test: run a scenario that simulate the scenario
      (PTS is always set to the past)
Bug: 123780024
Change-Id: Ib47bc5ebc50136c54b29bd301ad8d059f3dea947
parent 5ef8f96e

services/surfaceflinger/BufferQueueLayer.cpp

+20 −1
Original line number Diff line number Diff line
@@ -235,9 +235,28 @@ status_t BufferQueueLayer::updateTexImage(bool& recomputeVisibleRegions, nsecs_t 
    const nsecs_t expectedPresentTime = mFlinger->mUseScheduler

            ? mFlinger->mScheduler->mPrimaryDispSync->expectedPresentTime()

            : mFlinger->mPrimaryDispSync->expectedPresentTime();



    // updateTexImage() below might drop the some buffers at the head of the queue if there is a

    // buffer behind them which is timely to be presented. However this buffer may not be signaled

    // yet. The code below makes sure that this wouldn't happen by setting maxFrameNumber to the

    // last buffer that was signaled.

    uint64_t lastSignaledFrameNumber = mLastFrameNumberReceived;

    {

        Mutex::Autolock lock(mQueueItemLock);

        for (int i = 0; i < mQueueItems.size(); i++) {

            bool fenceSignaled =

                    mQueueItems[i].mFenceTime->getSignalTime() != Fence::SIGNAL_TIME_PENDING;

            if (!fenceSignaled) {

                break;

            }

            lastSignaledFrameNumber = mQueueItems[i].mFrameNumber;

        }

    }

    const uint64_t maxFrameNumberToAcquire =

            std::min(mLastFrameNumberReceived.load(), lastSignaledFrameNumber);

    status_t updateResult =

            mConsumer->updateTexImage(&r, expectedPresentTime, &mAutoRefresh, &queuedBuffer,

                                      mLastFrameNumberReceived, releaseFence);

                                      maxFrameNumberToAcquire, releaseFence);

    if (updateResult == BufferQueue::PRESENT_LATER) {

        // Producer doesn't want buffer to be displayed yet.  Signal a

        // layer update so we check again at the next opportunity.