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Commit 90553da7 authored by Brian Lindahl's avatar Brian Lindahl
Browse files

Clear HWC layer buffer slots by assiging a placeholder buffer 

When buffers are discarded by SurfaceFlinger clients, the memory should
be free'd immediately. This includes clearing references to them from
within the implementation of Composer HAL, specifically in cache slots
associated with the layer.

Since there is no HAL API to clear the slot directly, prior to writing
any other buffer to the layer, we set the layer's buffer multiple times
to a placeholder buffer, using each of the slot numbers that need to be
cleared. This replaces the reference to the client-discarded buffer
inside Composer HAL with a reference to the placeholder buffer, causing
the reference count to drop, allowing the buffer memory to be freed.

Bug: 258196272
Test: atest OutputLayerUncacheBufferTest
Change-Id: Id85482e8859490566f0eedbd8d8729c47a7349fb
parent d1d22742

services/surfaceflinger/CompositionEngine/include/compositionengine/mock/LayerFE.h

+1 −0
Original line number Diff line number Diff line
@@ -36,6 +36,7 @@ private: 
    // sp<StrictMock<LayerFE>>::make()

    friend class sp<LayerFE>;

    friend class testing::StrictMock<LayerFE>;

    friend class testing::NiceMock<LayerFE>;



public:

    virtual ~LayerFE();

services/surfaceflinger/CompositionEngine/src/HwcBufferCache.cpp

+1 −1
Original line number Diff line number Diff line
@@ -22,7 +22,7 @@ 
namespace android::compositionengine::impl {



HwcBufferCache::HwcBufferCache() {

    for (uint32_t i = 0; i < kMaxLayerBufferCount; i++) {

    for (uint32_t i = kMaxLayerBufferCount; i-- > 0;) {

        mFreeSlots.push(i);

    }

}

services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp

+6 −2
Original line number Diff line number Diff line
@@ -618,8 +618,12 @@ void OutputLayer::uncacheBuffers(std::vector<uint64_t> const& bufferIdsToUncache 
    }



    for (auto bufferId : bufferIdsToUncache) {

        state.hwc->hwcBufferCache.uncache(bufferId);

        // TODO(b/258196272): send uncache requests to Composer HAL

        uint32_t slot = state.hwc->hwcBufferCache.uncache(bufferId);

        if (slot != UINT32_MAX && state.hwc->hwcLayer) {

            hal::Error error = state.hwc->hwcLayer->clearBufferSlot(slot);

            ALOGE("[%s] Failed to clear buffer slot %d: %s (%d)", getLayerFE().getDebugName(), slot,

                  to_string(error).c_str(), static_cast<int32_t>(error));

        }

    }

}

services/surfaceflinger/CompositionEngine/tests/MockHWC2.h

+1 −0
Original line number Diff line number Diff line
@@ -56,6 +56,7 @@ public: 
    MOCK_METHOD3(setBuffer,

                 Error(uint32_t, const android::sp<android::GraphicBuffer>&,

                       const android::sp<android::Fence>&));

    MOCK_METHOD1(clearBufferSlot, Error(uint32_t));

    MOCK_METHOD1(setSurfaceDamage, Error(const android::Region&));

    MOCK_METHOD1(setBlendMode, Error(hal::BlendMode));

    MOCK_METHOD1(setColor, Error(aidl::android::hardware::graphics::composer3::Color));

services/surfaceflinger/CompositionEngine/tests/OutputLayerTest.cpp

+96 −46

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