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
diff --git a/services/surfaceflinger/DisplayHardware/AidlComposerHal.cpp b/services/surfaceflinger/DisplayHardware/AidlComposerHal.cpp
index 800e36d..a93bd95 100644
--- a/services/surfaceflinger/DisplayHardware/AidlComposerHal.cpp
+++ b/services/surfaceflinger/DisplayHardware/AidlComposerHal.cpp
@@ -232,6 +232,17 @@
addReader(translate<Display>(kSingleReaderKey));
+ // TODO(b/262041682): When using new API to clear buffer slots, don't allocate this buffer.
+ mClearSlotBuffer = sp<GraphicBuffer>::make(1, 1, PIXEL_FORMAT_RGBX_8888,
+ GraphicBuffer::USAGE_HW_COMPOSER |
+ GraphicBuffer::USAGE_SW_READ_OFTEN |
+ GraphicBuffer::USAGE_SW_WRITE_OFTEN,
+ "AidlComposer");
+ if (!mClearSlotBuffer || mClearSlotBuffer->initCheck() != ::android::OK) {
+ LOG_ALWAYS_FATAL("Failed to allocate a buffer for clearing layer buffer slots");
+ return;
+ }
+
ALOGI("Loaded AIDL composer3 HAL service");
}
@@ -809,6 +820,20 @@
return error;
}
+Error AidlComposer::clearLayerBufferSlot(Display display, Layer layer, uint32_t slot) {
+ Error error = Error::NONE;
+ mMutex.lock_shared();
+ if (auto writer = getWriter(display)) {
+ writer->get().setLayerBufferWithNewCommand(translate<int64_t>(display),
+ translate<int64_t>(layer), slot,
+ mClearSlotBuffer->handle, /*fence*/ -1);
+ } else {
+ error = Error::BAD_DISPLAY;
+ }
+ mMutex.unlock_shared();
+ return error;
+}
+
Error AidlComposer::setLayerSurfaceDamage(Display display, Layer layer,
const std::vector<IComposerClient::Rect>& damage) {
Error error = Error::NONE;
diff --git a/services/surfaceflinger/DisplayHardware/AidlComposerHal.h b/services/surfaceflinger/DisplayHardware/AidlComposerHal.h
index 2a043fd..5128648 100644
--- a/services/surfaceflinger/DisplayHardware/AidlComposerHal.h
+++ b/services/surfaceflinger/DisplayHardware/AidlComposerHal.h
@@ -143,6 +143,7 @@
/* see setClientTarget for the purpose of slot */
Error setLayerBuffer(Display display, Layer layer, uint32_t slot,
const sp<GraphicBuffer>& buffer, int acquireFence) override;
+ Error clearLayerBufferSlot(Display display, Layer layer, uint32_t slot) override;
Error setLayerSurfaceDamage(Display display, Layer layer,
const std::vector<IComposerClient::Rect>& damage) override;
Error setLayerBlendMode(Display display, Layer layer, IComposerClient::BlendMode mode) override;
@@ -280,6 +281,9 @@
// threading annotations.
ftl::SharedMutex mMutex;
+ // Buffer slots for layers are cleared by setting the slot buffer to this buffer.
+ sp<GraphicBuffer> mClearSlotBuffer;
+
// Aidl interface
using AidlIComposer = aidl::android::hardware::graphics::composer3::IComposer;
using AidlIComposerClient = aidl::android::hardware::graphics::composer3::IComposerClient;
diff --git a/services/surfaceflinger/DisplayHardware/ComposerHal.h b/services/surfaceflinger/DisplayHardware/ComposerHal.h
index ec23935..821025c 100644
--- a/services/surfaceflinger/DisplayHardware/ComposerHal.h
+++ b/services/surfaceflinger/DisplayHardware/ComposerHal.h
@@ -179,6 +179,7 @@
/* see setClientTarget for the purpose of slot */
virtual Error setLayerBuffer(Display display, Layer layer, uint32_t slot,
const sp<GraphicBuffer>& buffer, int acquireFence) = 0;
+ virtual Error clearLayerBufferSlot(Display display, Layer layer, uint32_t slot) = 0;
virtual Error setLayerSurfaceDamage(Display display, Layer layer,
const std::vector<IComposerClient::Rect>& damage) = 0;
virtual Error setLayerBlendMode(Display display, Layer layer,
diff --git a/services/surfaceflinger/DisplayHardware/HWC2.cpp b/services/surfaceflinger/DisplayHardware/HWC2.cpp
index d0126d0..b5f91a6 100644
--- a/services/surfaceflinger/DisplayHardware/HWC2.cpp
+++ b/services/surfaceflinger/DisplayHardware/HWC2.cpp
@@ -717,6 +717,14 @@
return static_cast<Error>(intError);
}
+Error Layer::clearBufferSlot(uint32_t slot) {
+ if (CC_UNLIKELY(!mDisplay)) {
+ return Error::BAD_DISPLAY;
+ }
+ auto intError = mComposer.clearLayerBufferSlot(mDisplay->getId(), mId, slot);
+ return static_cast<Error>(intError);
+}
+
Error Layer::setSurfaceDamage(const Region& damage)
{
if (CC_UNLIKELY(!mDisplay)) {
diff --git a/services/surfaceflinger/DisplayHardware/HWC2.h b/services/surfaceflinger/DisplayHardware/HWC2.h
index 4971d19..13edb13 100644
--- a/services/surfaceflinger/DisplayHardware/HWC2.h
+++ b/services/surfaceflinger/DisplayHardware/HWC2.h
@@ -310,6 +310,7 @@
[[nodiscard]] virtual hal::Error setBuffer(uint32_t slot,
const android::sp<android::GraphicBuffer>& buffer,
const android::sp<android::Fence>& acquireFence) = 0;
+ [[nodiscard]] virtual hal::Error clearBufferSlot(uint32_t slot) = 0;
[[nodiscard]] virtual hal::Error setSurfaceDamage(const android::Region& damage) = 0;
[[nodiscard]] virtual hal::Error setBlendMode(hal::BlendMode mode) = 0;
@@ -360,6 +361,7 @@
hal::Error setCursorPosition(int32_t x, int32_t y) override;
hal::Error setBuffer(uint32_t slot, const android::sp<android::GraphicBuffer>& buffer,
const android::sp<android::Fence>& acquireFence) override;
+ hal::Error clearBufferSlot(uint32_t slot) override;
hal::Error setSurfaceDamage(const android::Region& damage) override;
hal::Error setBlendMode(hal::BlendMode mode) override;
diff --git a/services/surfaceflinger/DisplayHardware/HidlComposerHal.cpp b/services/surfaceflinger/DisplayHardware/HidlComposerHal.cpp
index b607df0..9a49d94 100644
--- a/services/surfaceflinger/DisplayHardware/HidlComposerHal.cpp
+++ b/services/surfaceflinger/DisplayHardware/HidlComposerHal.cpp
@@ -186,9 +186,22 @@
return out;
}
+sp<GraphicBuffer> allocateClearSlotBuffer() {
+ sp<GraphicBuffer> buffer = sp<GraphicBuffer>::make(1, 1, PIXEL_FORMAT_RGBX_8888,
+ GraphicBuffer::USAGE_HW_COMPOSER |
+ GraphicBuffer::USAGE_SW_READ_OFTEN |
+ GraphicBuffer::USAGE_SW_WRITE_OFTEN,
+ "HidlComposer");
+ if (!buffer || buffer->initCheck() != ::android::OK) {
+ return nullptr;
+ }
+ return std::move(buffer);
+}
+
} // anonymous namespace
-HidlComposer::HidlComposer(const std::string& serviceName) : mWriter(kWriterInitialSize) {
+HidlComposer::HidlComposer(const std::string& serviceName)
+ : mClearSlotBuffer(allocateClearSlotBuffer()), mWriter(kWriterInitialSize) {
mComposer = V2_1::IComposer::getService(serviceName);
if (mComposer == nullptr) {
@@ -230,6 +243,11 @@
if (mClient == nullptr) {
LOG_ALWAYS_FATAL("failed to create composer client");
}
+
+ if (!mClearSlotBuffer) {
+ LOG_ALWAYS_FATAL("Failed to allocate a buffer for clearing layer buffer slots");
+ return;
+ }
}
bool HidlComposer::isSupported(OptionalFeature feature) const {
@@ -694,6 +712,13 @@
return Error::NONE;
}
+Error HidlComposer::clearLayerBufferSlot(Display display, Layer layer, uint32_t slot) {
+ mWriter.selectDisplay(display);
+ mWriter.selectLayer(layer);
+ mWriter.setLayerBuffer(slot, mClearSlotBuffer->handle, /*fence*/ -1);
+ return Error::NONE;
+}
+
Error HidlComposer::setLayerSurfaceDamage(Display display, Layer layer,
const std::vector<IComposerClient::Rect>& damage) {
mWriter.selectDisplay(display);
diff --git a/services/surfaceflinger/DisplayHardware/HidlComposerHal.h b/services/surfaceflinger/DisplayHardware/HidlComposerHal.h
index 3602bbb..dc115b2 100644
--- a/services/surfaceflinger/DisplayHardware/HidlComposerHal.h
+++ b/services/surfaceflinger/DisplayHardware/HidlComposerHal.h
@@ -248,6 +248,7 @@
/* see setClientTarget for the purpose of slot */
Error setLayerBuffer(Display display, Layer layer, uint32_t slot,
const sp<GraphicBuffer>& buffer, int acquireFence) override;
+ Error clearLayerBufferSlot(Display display, Layer layer, uint32_t slot) override;
Error setLayerSurfaceDamage(Display display, Layer layer,
const std::vector<IComposerClient::Rect>& damage) override;
Error setLayerBlendMode(Display display, Layer layer, IComposerClient::BlendMode mode) override;
@@ -362,6 +363,9 @@
sp<V2_3::IComposerClient> mClient_2_3;
sp<IComposerClient> mClient_2_4;
+ // Buffer slots for layers are cleared by setting the slot buffer to this buffer.
+ sp<GraphicBuffer> mClearSlotBuffer;
+
// 64KiB minus a small space for metadata such as read/write pointers
static constexpr size_t kWriterInitialSize = 64 * 1024 / sizeof(uint32_t) - 16;
// Max number of buffers that may be cached for a given layer