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Commit 1ce6581a authored by Dan Stoza's avatar Dan Stoza
Browse files

SF: Only latch buffers after fence signals 

Changes SurfaceFlinger to only latch a buffer after its corresponding
acquire fence has signaled. This will enable us to move
SurfaceFlinger closer to vsync since there is no risk of fence waits
blocking composition.

Bug: 29413700
Change-Id: I26f4fd600c1611b8d736ec654d1f0f02cf69ae5f
parent 0ade247d

services/surfaceflinger/Layer.cpp

+28 −1
Original line number Diff line number Diff line
@@ -1100,6 +1100,25 @@ uint64_t Layer::getHeadFrameNumber() const { 
    }

}



bool Layer::headFenceHasSignaled() const {

#ifdef USE_HWC2

    Mutex::Autolock lock(mQueueItemLock);

    if (mQueueItems.empty()) {

        return true;

    }

    if (mQueueItems[0].mIsDroppable) {

        // Even though this buffer's fence may not have signaled yet, it could

        // be replaced by another buffer before it has a chance to, which means

        // that it's possible to get into a situation where a buffer is never

        // able to be latched. To avoid this, grab this buffer anyway.

        return true;

    }

    return mQueueItems[0].mFence->getSignalTime() != INT64_MAX;

#else

    return true;

#endif

}



bool Layer::addSyncPoint(const std::shared_ptr<SyncPoint>& point) {

    if (point->getFrameNumber() <= mCurrentFrameNumber) {

        // Don't bother with a SyncPoint, since we've already latched the
@@ -1357,9 +1376,10 @@ bool Layer::applyPendingStates(State* stateToCommit) { 


void Layer::notifyAvailableFrames() {

    auto headFrameNumber = getHeadFrameNumber();

    bool headFenceSignaled = headFenceHasSignaled();

    Mutex::Autolock lock(mLocalSyncPointMutex);

    for (auto& point : mLocalSyncPoints) {

        if (headFrameNumber >= point->getFrameNumber()) {

        if (headFrameNumber >= point->getFrameNumber() && headFenceSignaled) {

            point->setFrameAvailable();

        }

    }
@@ -1756,6 +1776,13 @@ Region Layer::latchBuffer(bool& recomputeVisibleRegions) 
            return outDirtyRegion;

        }



        // If the head buffer's acquire fence hasn't signaled yet, return and

        // try again later

        if (!headFenceHasSignaled()) {

            mFlinger->signalLayerUpdate();

            return outDirtyRegion;

        }



        // Capture the old state of the layer for comparisons later

        const State& s(getDrawingState());

        const bool oldOpacity = isOpaque(s);

services/surfaceflinger/Layer.h

+1 −0
Original line number Diff line number Diff line
@@ -510,6 +510,7 @@ private: 
    std::list<std::shared_ptr<SyncPoint>> mRemoteSyncPoints;



    uint64_t getHeadFrameNumber() const;

    bool headFenceHasSignaled() const;



    // Returns false if the relevant frame has already been latched

    bool addSyncPoint(const std::shared_ptr<SyncPoint>& point);