libs/gui/BLASTBufferQueue.cpp

/*
 * Copyright (C) 2019 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#undef LOG_TAG
#define LOG_TAG "BLASTBufferQueue"

#define ATRACE_TAG ATRACE_TAG_GRAPHICS
//#define LOG_NDEBUG 0

#include <cutils/atomic.h>
#include <gui/BLASTBufferQueue.h>
#include <gui/BufferItemConsumer.h>
#include <gui/BufferQueueConsumer.h>
#include <gui/BufferQueueCore.h>
#include <gui/BufferQueueProducer.h>
#include <gui/GLConsumer.h>
#include <gui/IProducerListener.h>
#include <gui/Surface.h>
#include <gui/TraceUtils.h>
#include <utils/Singleton.h>
#include <utils/Trace.h>

#include <private/gui/ComposerService.h>
#include <private/gui/ComposerServiceAIDL.h>

#include <android-base/thread_annotations.h>
#include <chrono>

using namespace std::chrono_literals;

namespace {
inline const char* boolToString(bool b) {
    return b ? "true" : "false";
}
} // namespace

namespace android {

// Macros to include adapter info in log messages
#define BQA_LOGD(x, ...) \
    ALOGD("[%s](f:%u,a:%u) " x, mName.c_str(), mNumFrameAvailable, mNumAcquired, ##__VA_ARGS__)
#define BQA_LOGV(x, ...) \
    ALOGV("[%s](f:%u,a:%u) " x, mName.c_str(), mNumFrameAvailable, mNumAcquired, ##__VA_ARGS__)
// enable logs for a single layer
//#define BQA_LOGV(x, ...) \
//    ALOGV_IF((strstr(mName.c_str(), "SurfaceView") != nullptr), "[%s](f:%u,a:%u) " x, \
//              mName.c_str(), mNumFrameAvailable, mNumAcquired, ##__VA_ARGS__)
#define BQA_LOGE(x, ...) \
    ALOGE("[%s](f:%u,a:%u) " x, mName.c_str(), mNumFrameAvailable, mNumAcquired, ##__VA_ARGS__)

#define BBQ_TRACE(x, ...)                                                                  \
    ATRACE_FORMAT("%s - %s(f:%u,a:%u)" x, __FUNCTION__, mName.c_str(), mNumFrameAvailable, \
                  mNumAcquired, ##__VA_ARGS__)

#define UNIQUE_LOCK_WITH_ASSERTION(mutex) \
    std::unique_lock _lock{mutex};        \
    base::ScopedLockAssertion assumeLocked(mutex);

void BLASTBufferItemConsumer::onDisconnect() {
    Mutex::Autolock lock(mMutex);
    mPreviouslyConnected = mCurrentlyConnected;
    mCurrentlyConnected = false;
    if (mPreviouslyConnected) {
        mDisconnectEvents.push(mCurrentFrameNumber);
    }
    mFrameEventHistory.onDisconnect();
}

void BLASTBufferItemConsumer::addAndGetFrameTimestamps(const NewFrameEventsEntry* newTimestamps,
                                                       FrameEventHistoryDelta* outDelta) {
    Mutex::Autolock lock(mMutex);
    if (newTimestamps) {
        // BufferQueueProducer only adds a new timestamp on
        // queueBuffer
        mCurrentFrameNumber = newTimestamps->frameNumber;
        mFrameEventHistory.addQueue(*newTimestamps);
    }
    if (outDelta) {
        // frame event histories will be processed
        // only after the producer connects and requests
        // deltas for the first time.  Forward this intent
        // to SF-side to turn event processing back on
        mPreviouslyConnected = mCurrentlyConnected;
        mCurrentlyConnected = true;
        mFrameEventHistory.getAndResetDelta(outDelta);
    }
}

void BLASTBufferItemConsumer::updateFrameTimestamps(uint64_t frameNumber, nsecs_t refreshStartTime,
                                                    const sp<Fence>& glDoneFence,
                                                    const sp<Fence>& presentFence,
                                                    const sp<Fence>& prevReleaseFence,
                                                    CompositorTiming compositorTiming,
                                                    nsecs_t latchTime, nsecs_t dequeueReadyTime) {
    Mutex::Autolock lock(mMutex);

    // if the producer is not connected, don't bother updating,
    // the next producer that connects won't access this frame event
    if (!mCurrentlyConnected) return;
    std::shared_ptr<FenceTime> glDoneFenceTime = std::make_shared<FenceTime>(glDoneFence);
    std::shared_ptr<FenceTime> presentFenceTime = std::make_shared<FenceTime>(presentFence);
    std::shared_ptr<FenceTime> releaseFenceTime = std::make_shared<FenceTime>(prevReleaseFence);

    mFrameEventHistory.addLatch(frameNumber, latchTime);
    mFrameEventHistory.addRelease(frameNumber, dequeueReadyTime, std::move(releaseFenceTime));
    mFrameEventHistory.addPreComposition(frameNumber, refreshStartTime);
    mFrameEventHistory.addPostComposition(frameNumber, glDoneFenceTime, presentFenceTime,
                                          compositorTiming);
}

void BLASTBufferItemConsumer::getConnectionEvents(uint64_t frameNumber, bool* needsDisconnect) {
    bool disconnect = false;
    Mutex::Autolock lock(mMutex);
    while (!mDisconnectEvents.empty() && mDisconnectEvents.front() <= frameNumber) {
        disconnect = true;
        mDisconnectEvents.pop();
    }
    if (needsDisconnect != nullptr) *needsDisconnect = disconnect;
}

void BLASTBufferItemConsumer::onSidebandStreamChanged() {
    sp<BLASTBufferQueue> bbq = mBLASTBufferQueue.promote();
    if (bbq != nullptr) {
        sp<NativeHandle> stream = getSidebandStream();
        bbq->setSidebandStream(stream);
    }
}

BLASTBufferQueue::BLASTBufferQueue(const std::string& name, bool updateDestinationFrame)
      : mSurfaceControl(nullptr),
        mSize(1, 1),
        mRequestedSize(mSize),
        mFormat(PIXEL_FORMAT_RGBA_8888),
        mTransactionReadyCallback(nullptr),
        mSyncTransaction(nullptr),
        mUpdateDestinationFrame(updateDestinationFrame) {
    createBufferQueue(&mProducer, &mConsumer);
    // since the adapter is in the client process, set dequeue timeout
    // explicitly so that dequeueBuffer will block
    mProducer->setDequeueTimeout(std::numeric_limits<int64_t>::max());

    // safe default, most producers are expected to override this
    mProducer->setMaxDequeuedBufferCount(2);
    mBufferItemConsumer = new BLASTBufferItemConsumer(mConsumer,
                                                      GraphicBuffer::USAGE_HW_COMPOSER |
                                                              GraphicBuffer::USAGE_HW_TEXTURE,
                                                      1, false, this);
    static std::atomic<uint32_t> nextId = 0;
    mProducerId = nextId++;
    mName = name + "#" + std::to_string(mProducerId);
    auto consumerName = mName + "(BLAST Consumer)" + std::to_string(mProducerId);
    mQueuedBufferTrace = "QueuedBuffer - " + mName + "BLAST#" + std::to_string(mProducerId);
    mBufferItemConsumer->setName(String8(consumerName.c_str()));
    mBufferItemConsumer->setFrameAvailableListener(this);

    ComposerServiceAIDL::getComposerService()->getMaxAcquiredBufferCount(&mMaxAcquiredBuffers);
    mBufferItemConsumer->setMaxAcquiredBufferCount(mMaxAcquiredBuffers);
    mCurrentMaxAcquiredBufferCount = mMaxAcquiredBuffers;
    mNumAcquired = 0;
    mNumFrameAvailable = 0;

    TransactionCompletedListener::getInstance()->addQueueStallListener(
            [&](const std::string& reason) {
                std::function<void(const std::string&)> callbackCopy;
                {
                    std::unique_lock _lock{mMutex};
                    callbackCopy = mTransactionHangCallback;
                }
                if (callbackCopy) callbackCopy(reason);
            },
            this);

    BQA_LOGV("BLASTBufferQueue created");
}

BLASTBufferQueue::BLASTBufferQueue(const std::string& name, const sp<SurfaceControl>& surface,
                                   int width, int height, int32_t format)
      : BLASTBufferQueue(name) {
    update(surface, width, height, format);
}

BLASTBufferQueue::~BLASTBufferQueue() {
    TransactionCompletedListener::getInstance()->removeQueueStallListener(this);
    if (mPendingTransactions.empty()) {
        return;
    }
    BQA_LOGE("Applying pending transactions on dtor %d",
             static_cast<uint32_t>(mPendingTransactions.size()));
    SurfaceComposerClient::Transaction t;
    mergePendingTransactions(&t, std::numeric_limits<uint64_t>::max() /* frameNumber */);
    // All transactions on our apply token are one-way. See comment on mAppliedLastTransaction
    t.setApplyToken(mApplyToken).apply(false, true);

    if (mTransactionReadyCallback) {
        mTransactionReadyCallback(mSyncTransaction);
    }
}

void BLASTBufferQueue::update(const sp<SurfaceControl>& surface, uint32_t width, uint32_t height,
                              int32_t format) {
    LOG_ALWAYS_FATAL_IF(surface == nullptr, "BLASTBufferQueue: mSurfaceControl must not be NULL");

    std::lock_guard _lock{mMutex};
    if (mFormat != format) {
        mFormat = format;
        mBufferItemConsumer->setDefaultBufferFormat(convertBufferFormat(format));
    }

    const bool surfaceControlChanged = !SurfaceControl::isSameSurface(mSurfaceControl, surface);
    if (surfaceControlChanged && mSurfaceControl != nullptr) {
        BQA_LOGD("Updating SurfaceControl without recreating BBQ");
    }
    bool applyTransaction = false;

    // Always update the native object even though they might have the same layer handle, so we can
    // get the updated transform hint from WM.
    mSurfaceControl = surface;
    SurfaceComposerClient::Transaction t;
    if (surfaceControlChanged) {
        t.setFlags(mSurfaceControl, layer_state_t::eEnableBackpressure,
                   layer_state_t::eEnableBackpressure);
        applyTransaction = true;
    }
    mTransformHint = mSurfaceControl->getTransformHint();
    mBufferItemConsumer->setTransformHint(mTransformHint);
    BQA_LOGV("update width=%d height=%d format=%d mTransformHint=%d", width, height, format,
             mTransformHint);

    ui::Size newSize(width, height);
    if (mRequestedSize != newSize) {
        mRequestedSize.set(newSize);
        mBufferItemConsumer->setDefaultBufferSize(mRequestedSize.width, mRequestedSize.height);
        if (mLastBufferInfo.scalingMode != NATIVE_WINDOW_SCALING_MODE_FREEZE) {
            // If the buffer supports scaling, update the frame immediately since the client may
            // want to scale the existing buffer to the new size.
            mSize = mRequestedSize;
            if (mUpdateDestinationFrame) {
                t.setDestinationFrame(mSurfaceControl, Rect(newSize));
                applyTransaction = true;
            }
        }
    }
    if (applyTransaction) {
        // All transactions on our apply token are one-way. See comment on mAppliedLastTransaction
        t.setApplyToken(mApplyToken).apply(false, true);
    }
}

static std::optional<SurfaceControlStats> findMatchingStat(
        const std::vector<SurfaceControlStats>& stats, const sp<SurfaceControl>& sc) {
    for (auto stat : stats) {
        if (SurfaceControl::isSameSurface(sc, stat.surfaceControl)) {
            return stat;
        }
    }
    return std::nullopt;
}

static void transactionCommittedCallbackThunk(void* context, nsecs_t latchTime,
                                              const sp<Fence>& presentFence,
                                              const std::vector<SurfaceControlStats>& stats) {
    if (context == nullptr) {
        return;
    }
    sp<BLASTBufferQueue> bq = static_cast<BLASTBufferQueue*>(context);
    bq->transactionCommittedCallback(latchTime, presentFence, stats);
}

void BLASTBufferQueue::transactionCommittedCallback(nsecs_t /*latchTime*/,
                                                    const sp<Fence>& /*presentFence*/,
                                                    const std::vector<SurfaceControlStats>& stats) {
    {
        std::lock_guard _lock{mMutex};
        BBQ_TRACE();
        BQA_LOGV("transactionCommittedCallback");
        if (!mSurfaceControlsWithPendingCallback.empty()) {
            sp<SurfaceControl> pendingSC = mSurfaceControlsWithPendingCallback.front();
            std::optional<SurfaceControlStats> stat = findMatchingStat(stats, pendingSC);
            if (stat) {
                uint64_t currFrameNumber = stat->frameEventStats.frameNumber;

                // We need to check if we were waiting for a transaction callback in order to
                // process any pending buffers and unblock. It's possible to get transaction
                // callbacks for previous requests so we need to ensure that there are no pending
                // frame numbers that were in a sync. We remove the frame from mSyncedFrameNumbers
                // set and then check if it's empty. If there are no more pending syncs, we can
                // proceed with flushing the shadow queue.
                // We also want to check if mSyncTransaction is null because it's possible another
                // sync request came in while waiting, but it hasn't started processing yet. In that
                // case, we don't actually want to flush the frames in between since they will get
                // processed and merged with the sync transaction and released earlier than if they
                // were sent to SF
                mSyncedFrameNumbers.erase(currFrameNumber);
                if (mSyncedFrameNumbers.empty() && mSyncTransaction == nullptr) {
                    flushShadowQueue();
                }
            } else {
                BQA_LOGE("Failed to find matching SurfaceControl in transactionCommittedCallback");
            }
        } else {
            BQA_LOGE("No matching SurfaceControls found: mSurfaceControlsWithPendingCallback was "
                     "empty.");
        }
        decStrong((void*)transactionCommittedCallbackThunk);
    }
}

static void transactionCallbackThunk(void* context, nsecs_t latchTime,
                                     const sp<Fence>& presentFence,
                                     const std::vector<SurfaceControlStats>& stats) {
    if (context == nullptr) {
        return;
    }
    sp<BLASTBufferQueue> bq = static_cast<BLASTBufferQueue*>(context);
    bq->transactionCallback(latchTime, presentFence, stats);
}

void BLASTBufferQueue::transactionCallback(nsecs_t /*latchTime*/, const sp<Fence>& /*presentFence*/,
                                           const std::vector<SurfaceControlStats>& stats) {
    {
        std::lock_guard _lock{mMutex};
        BBQ_TRACE();
        BQA_LOGV("transactionCallback");

        if (!mSurfaceControlsWithPendingCallback.empty()) {
            sp<SurfaceControl> pendingSC = mSurfaceControlsWithPendingCallback.front();
            mSurfaceControlsWithPendingCallback.pop();
            std::optional<SurfaceControlStats> statsOptional = findMatchingStat(stats, pendingSC);
            if (statsOptional) {
                SurfaceControlStats stat = *statsOptional;
                if (stat.transformHint) {
                    mTransformHint = *stat.transformHint;
                    mBufferItemConsumer->setTransformHint(mTransformHint);
                    BQA_LOGV("updated mTransformHint=%d", mTransformHint);
                }
                // Update frametime stamps if the frame was latched and presented, indicated by a
                // valid latch time.
                if (stat.latchTime > 0) {
                    mBufferItemConsumer
                            ->updateFrameTimestamps(stat.frameEventStats.frameNumber,
                                                    stat.frameEventStats.refreshStartTime,
                                                    stat.frameEventStats.gpuCompositionDoneFence,
                                                    stat.presentFence, stat.previousReleaseFence,
                                                    stat.frameEventStats.compositorTiming,
                                                    stat.latchTime,
                                                    stat.frameEventStats.dequeueReadyTime);
                }
                auto currFrameNumber = stat.frameEventStats.frameNumber;
                std::vector<ReleaseCallbackId> staleReleases;
                for (const auto& [key, value]: mSubmitted) {
                    if (currFrameNumber > key.framenumber) {
                        staleReleases.push_back(key);
                    }
                }
                for (const auto& staleRelease : staleReleases) {
                    releaseBufferCallbackLocked(staleRelease,
                                                stat.previousReleaseFence
                                                        ? stat.previousReleaseFence
                                                        : Fence::NO_FENCE,
                                                stat.currentMaxAcquiredBufferCount,
                                                true /* fakeRelease */);
                }
            } else {
                BQA_LOGE("Failed to find matching SurfaceControl in transactionCallback");
            }
        } else {
            BQA_LOGE("No matching SurfaceControls found: mSurfaceControlsWithPendingCallback was "
                     "empty.");
        }

        decStrong((void*)transactionCallbackThunk);
    }
}

// Unlike transactionCallbackThunk the release buffer callback does not extend the life of the
// BBQ. This is because if the BBQ is destroyed, then the buffers will be released by the client.
// So we pass in a weak pointer to the BBQ and if it still alive, then we release the buffer.
// Otherwise, this is a no-op.
static void releaseBufferCallbackThunk(wp<BLASTBufferQueue> context, const ReleaseCallbackId& id,
                                       const sp<Fence>& releaseFence,
                                       std::optional<uint32_t> currentMaxAcquiredBufferCount) {
    sp<BLASTBufferQueue> blastBufferQueue = context.promote();
    if (blastBufferQueue) {
        blastBufferQueue->releaseBufferCallback(id, releaseFence, currentMaxAcquiredBufferCount);
    } else {
        ALOGV("releaseBufferCallbackThunk %s blastBufferQueue is dead", id.to_string().c_str());
    }
}

void BLASTBufferQueue::flushShadowQueue() {
    BQA_LOGV("flushShadowQueue");
    int numFramesToFlush = mNumFrameAvailable;
    while (numFramesToFlush > 0) {
        acquireNextBufferLocked(std::nullopt);
        numFramesToFlush--;
    }
}

void BLASTBufferQueue::releaseBufferCallback(
        const ReleaseCallbackId& id, const sp<Fence>& releaseFence,
        std::optional<uint32_t> currentMaxAcquiredBufferCount) {
    std::lock_guard _lock{mMutex};
    BBQ_TRACE();
    releaseBufferCallbackLocked(id, releaseFence, currentMaxAcquiredBufferCount,
                                false /* fakeRelease */);
}

void BLASTBufferQueue::releaseBufferCallbackLocked(
        const ReleaseCallbackId& id, const sp<Fence>& releaseFence,
        std::optional<uint32_t> currentMaxAcquiredBufferCount, bool fakeRelease) {
    ATRACE_CALL();
    BQA_LOGV("releaseBufferCallback %s", id.to_string().c_str());

    // Calculate how many buffers we need to hold before we release them back
    // to the buffer queue. This will prevent higher latency when we are running
    // on a lower refresh rate than the max supported. We only do that for EGL
    // clients as others don't care about latency
    const auto it = mSubmitted.find(id);
    const bool isEGL = it != mSubmitted.end() && it->second.mApi == NATIVE_WINDOW_API_EGL;

    if (currentMaxAcquiredBufferCount) {
        mCurrentMaxAcquiredBufferCount = *currentMaxAcquiredBufferCount;
    }

    const uint32_t numPendingBuffersToHold =
            isEGL ? std::max(0, mMaxAcquiredBuffers - (int32_t)mCurrentMaxAcquiredBufferCount) : 0;

    auto rb = ReleasedBuffer{id, releaseFence};
    if (std::find(mPendingRelease.begin(), mPendingRelease.end(), rb) == mPendingRelease.end()) {
        mPendingRelease.emplace_back(rb);
        if (fakeRelease) {
            BQA_LOGE("Faking releaseBufferCallback from transactionCompleteCallback %" PRIu64,
                     id.framenumber);
            BBQ_TRACE("FakeReleaseCallback");
        }
    }

    // Release all buffers that are beyond the ones that we need to hold
    while (mPendingRelease.size() > numPendingBuffersToHold) {
        const auto releasedBuffer = mPendingRelease.front();
        mPendingRelease.pop_front();
        releaseBuffer(releasedBuffer.callbackId, releasedBuffer.releaseFence);
        // Don't process the transactions here if mSyncedFrameNumbers is not empty. That means
        // are still transactions that have sync buffers in them that have not been applied or
        // dropped. Instead, let onFrameAvailable handle processing them since it will merge with
        // the syncTransaction.
        if (mSyncedFrameNumbers.empty()) {
            acquireNextBufferLocked(std::nullopt);
        }
    }

    ATRACE_INT("PendingRelease", mPendingRelease.size());
    ATRACE_INT(mQueuedBufferTrace.c_str(),
               mNumFrameAvailable + mNumAcquired - mPendingRelease.size());
    mCallbackCV.notify_all();
}

void BLASTBufferQueue::releaseBuffer(const ReleaseCallbackId& callbackId,
                                     const sp<Fence>& releaseFence) {
    auto it = mSubmitted.find(callbackId);
    if (it == mSubmitted.end()) {
        BQA_LOGE("ERROR: releaseBufferCallback without corresponding submitted buffer %s",
                 callbackId.to_string().c_str());
        return;
    }
    mNumAcquired--;
    BBQ_TRACE("frame=%" PRIu64, callbackId.framenumber);
    BQA_LOGV("released %s", callbackId.to_string().c_str());
    mBufferItemConsumer->releaseBuffer(it->second, releaseFence);
    mSubmitted.erase(it);
    // Remove the frame number from mSyncedFrameNumbers since we can get a release callback
    // without getting a transaction committed if the buffer was dropped.
    mSyncedFrameNumbers.erase(callbackId.framenumber);
}

static ui::Size getBufferSize(const BufferItem& item) {
    uint32_t bufWidth = item.mGraphicBuffer->getWidth();
    uint32_t bufHeight = item.mGraphicBuffer->getHeight();

    // Take the buffer's orientation into account
    if (item.mTransform & ui::Transform::ROT_90) {
        std::swap(bufWidth, bufHeight);
    }
    return ui::Size(bufWidth, bufHeight);
}

status_t BLASTBufferQueue::acquireNextBufferLocked(
        const std::optional<SurfaceComposerClient::Transaction*> transaction) {
    // Check if we have frames available and we have not acquired the maximum number of buffers.
    // Even with this check, the consumer can fail to acquire an additional buffer if the consumer
    // has already acquired (mMaxAcquiredBuffers + 1) and the new buffer is not droppable. In this
    // case mBufferItemConsumer->acquireBuffer will return with NO_BUFFER_AVAILABLE.
    if (mNumFrameAvailable == 0) {
        BQA_LOGV("Can't acquire next buffer. No available frames");
        return BufferQueue::NO_BUFFER_AVAILABLE;
    }

    if (mNumAcquired >= (mMaxAcquiredBuffers + 2)) {
        BQA_LOGV("Can't acquire next buffer. Already acquired max frames %d max:%d + 2",
                 mNumAcquired, mMaxAcquiredBuffers);
        return BufferQueue::NO_BUFFER_AVAILABLE;
    }

    if (mSurfaceControl == nullptr) {
        BQA_LOGE("ERROR : surface control is null");
        return NAME_NOT_FOUND;
    }

    SurfaceComposerClient::Transaction localTransaction;
    bool applyTransaction = true;
    SurfaceComposerClient::Transaction* t = &localTransaction;
    if (transaction) {
        t = *transaction;
        applyTransaction = false;
    }

    BufferItem bufferItem;

    status_t status =
            mBufferItemConsumer->acquireBuffer(&bufferItem, 0 /* expectedPresent */, false);
    if (status == BufferQueue::NO_BUFFER_AVAILABLE) {
        BQA_LOGV("Failed to acquire a buffer, err=NO_BUFFER_AVAILABLE");
        return status;
    } else if (status != OK) {
        BQA_LOGE("Failed to acquire a buffer, err=%s", statusToString(status).c_str());
        return status;
    }

    auto buffer = bufferItem.mGraphicBuffer;
    mNumFrameAvailable--;
    BBQ_TRACE("frame=%" PRIu64, bufferItem.mFrameNumber);

    if (buffer == nullptr) {
        mBufferItemConsumer->releaseBuffer(bufferItem, Fence::NO_FENCE);
        BQA_LOGE("Buffer was empty");
        return BAD_VALUE;
    }

    if (rejectBuffer(bufferItem)) {
        BQA_LOGE("rejecting buffer:active_size=%dx%d, requested_size=%dx%d "
                 "buffer{size=%dx%d transform=%d}",
                 mSize.width, mSize.height, mRequestedSize.width, mRequestedSize.height,
                 buffer->getWidth(), buffer->getHeight(), bufferItem.mTransform);
        mBufferItemConsumer->releaseBuffer(bufferItem, Fence::NO_FENCE);
        return acquireNextBufferLocked(transaction);
    }

    mNumAcquired++;
    mLastAcquiredFrameNumber = bufferItem.mFrameNumber;
    ReleaseCallbackId releaseCallbackId(buffer->getId(), mLastAcquiredFrameNumber);
    mSubmitted[releaseCallbackId] = bufferItem;

    bool needsDisconnect = false;
    mBufferItemConsumer->getConnectionEvents(bufferItem.mFrameNumber, &needsDisconnect);

    // if producer disconnected before, notify SurfaceFlinger
    if (needsDisconnect) {
        t->notifyProducerDisconnect(mSurfaceControl);
    }

    // Ensure BLASTBufferQueue stays alive until we receive the transaction complete callback.
    incStrong((void*)transactionCallbackThunk);

    // Only update mSize for destination bounds if the incoming buffer matches the requested size.
    // Otherwise, it could cause stretching since the destination bounds will update before the
    // buffer with the new size is acquired.
    if (mRequestedSize == getBufferSize(bufferItem)) {
        mSize = mRequestedSize;
    }
    Rect crop = computeCrop(bufferItem);
    mLastBufferInfo.update(true /* hasBuffer */, bufferItem.mGraphicBuffer->getWidth(),
                           bufferItem.mGraphicBuffer->getHeight(), bufferItem.mTransform,
                           bufferItem.mScalingMode, crop);

    auto releaseBufferCallback =
            std::bind(releaseBufferCallbackThunk, wp<BLASTBufferQueue>(this) /* callbackContext */,
                      std::placeholders::_1, std::placeholders::_2, std::placeholders::_3);
    sp<Fence> fence = bufferItem.mFence ? new Fence(bufferItem.mFence->dup()) : Fence::NO_FENCE;
    t->setBuffer(mSurfaceControl, buffer, fence, bufferItem.mFrameNumber, mProducerId,
                 releaseBufferCallback);
    t->setDataspace(mSurfaceControl, static_cast<ui::Dataspace>(bufferItem.mDataSpace));
    t->setHdrMetadata(mSurfaceControl, bufferItem.mHdrMetadata);
    t->setSurfaceDamageRegion(mSurfaceControl, bufferItem.mSurfaceDamage);
    t->addTransactionCompletedCallback(transactionCallbackThunk, static_cast<void*>(this));

    mSurfaceControlsWithPendingCallback.push(mSurfaceControl);

    if (mUpdateDestinationFrame) {
        t->setDestinationFrame(mSurfaceControl, Rect(mSize));
    } else {
        const bool ignoreDestinationFrame =
                bufferItem.mScalingMode == NATIVE_WINDOW_SCALING_MODE_FREEZE;
        t->setFlags(mSurfaceControl,
                    ignoreDestinationFrame ? layer_state_t::eIgnoreDestinationFrame : 0,
                    layer_state_t::eIgnoreDestinationFrame);
    }
    t->setBufferCrop(mSurfaceControl, crop);
    t->setTransform(mSurfaceControl, bufferItem.mTransform);
    t->setTransformToDisplayInverse(mSurfaceControl, bufferItem.mTransformToDisplayInverse);
    t->setAutoRefresh(mSurfaceControl, bufferItem.mAutoRefresh);
    if (!bufferItem.mIsAutoTimestamp) {
        t->setDesiredPresentTime(bufferItem.mTimestamp);
    }

    // Drop stale frame timeline infos
    while (!mPendingFrameTimelines.empty() &&
           mPendingFrameTimelines.front().first < bufferItem.mFrameNumber) {
        ATRACE_FORMAT_INSTANT("dropping stale frameNumber: %" PRIu64 " vsyncId: %" PRId64,
                              mPendingFrameTimelines.front().first,
                              mPendingFrameTimelines.front().second.vsyncId);
        mPendingFrameTimelines.pop();
    }

    if (!mPendingFrameTimelines.empty() &&
        mPendingFrameTimelines.front().first == bufferItem.mFrameNumber) {
        ATRACE_FORMAT_INSTANT("Transaction::setFrameTimelineInfo frameNumber: %" PRIu64
                              " vsyncId: %" PRId64,
                              bufferItem.mFrameNumber,
                              mPendingFrameTimelines.front().second.vsyncId);
        t->setFrameTimelineInfo(mPendingFrameTimelines.front().second);
        mPendingFrameTimelines.pop();
    }

    {
        std::lock_guard _lock{mTimestampMutex};
        auto dequeueTime = mDequeueTimestamps.find(buffer->getId());
        if (dequeueTime != mDequeueTimestamps.end()) {
            Parcel p;
            p.writeInt64(dequeueTime->second);
            t->setMetadata(mSurfaceControl, gui::METADATA_DEQUEUE_TIME, p);
            mDequeueTimestamps.erase(dequeueTime);
        }
    }

    mergePendingTransactions(t, bufferItem.mFrameNumber);
    if (applyTransaction) {
        // All transactions on our apply token are one-way. See comment on mAppliedLastTransaction
        t->setApplyToken(mApplyToken).apply(false, true);
        mAppliedLastTransaction = true;
        mLastAppliedFrameNumber = bufferItem.mFrameNumber;
    } else {
        t->setBufferHasBarrier(mSurfaceControl, mLastAppliedFrameNumber);
        mAppliedLastTransaction = false;
    }

    BQA_LOGV("acquireNextBufferLocked size=%dx%d mFrameNumber=%" PRIu64
             " applyTransaction=%s mTimestamp=%" PRId64 "%s mPendingTransactions.size=%d"
             " graphicBufferId=%" PRIu64 "%s transform=%d",
             mSize.width, mSize.height, bufferItem.mFrameNumber, boolToString(applyTransaction),
             bufferItem.mTimestamp, bufferItem.mIsAutoTimestamp ? "(auto)" : "",
             static_cast<uint32_t>(mPendingTransactions.size()), bufferItem.mGraphicBuffer->getId(),
             bufferItem.mAutoRefresh ? " mAutoRefresh" : "", bufferItem.mTransform);
    return OK;
}

Rect BLASTBufferQueue::computeCrop(const BufferItem& item) {
    if (item.mScalingMode == NATIVE_WINDOW_SCALING_MODE_SCALE_CROP) {
        return GLConsumer::scaleDownCrop(item.mCrop, mSize.width, mSize.height);
    }
    return item.mCrop;
}

void BLASTBufferQueue::acquireAndReleaseBuffer() {
    BBQ_TRACE();
    BufferItem bufferItem;
    status_t status =
            mBufferItemConsumer->acquireBuffer(&bufferItem, 0 /* expectedPresent */, false);
    if (status != OK) {
        BQA_LOGE("Failed to acquire a buffer in acquireAndReleaseBuffer, err=%s",
                 statusToString(status).c_str());
        return;
    }
    mNumFrameAvailable--;
    mBufferItemConsumer->releaseBuffer(bufferItem, bufferItem.mFence);
}

void BLASTBufferQueue::onFrameAvailable(const BufferItem& item) {
    std::function<void(SurfaceComposerClient::Transaction*)> prevCallback = nullptr;
    SurfaceComposerClient::Transaction* prevTransaction = nullptr;

    {
        UNIQUE_LOCK_WITH_ASSERTION(mMutex);
        BBQ_TRACE();
        bool waitForTransactionCallback = !mSyncedFrameNumbers.empty();

        const bool syncTransactionSet = mTransactionReadyCallback != nullptr;
        BQA_LOGV("onFrameAvailable-start syncTransactionSet=%s", boolToString(syncTransactionSet));

        if (syncTransactionSet) {
            // If we are going to re-use the same mSyncTransaction, release the buffer that may
            // already be set in the Transaction. This is to allow us a free slot early to continue
            // processing a new buffer.
            if (!mAcquireSingleBuffer) {
                auto bufferData = mSyncTransaction->getAndClearBuffer(mSurfaceControl);
                if (bufferData) {
                    BQA_LOGD("Releasing previous buffer when syncing: framenumber=%" PRIu64,
                             bufferData->frameNumber);
                    releaseBuffer(bufferData->generateReleaseCallbackId(),
                                  bufferData->acquireFence);
                }
            }

            if (waitForTransactionCallback) {
                // We are waiting on a previous sync's transaction callback so allow another sync
                // transaction to proceed.
                //
                // We need to first flush out the transactions that were in between the two syncs.
                // We do this by merging them into mSyncTransaction so any buffer merging will get
                // a release callback invoked.
                while (mNumFrameAvailable > 0) {
                    // flush out the shadow queue
                    acquireAndReleaseBuffer();
                }
            } else {
                // Make sure the frame available count is 0 before proceeding with a sync to ensure
                // the correct frame is used for the sync. The only way mNumFrameAvailable would be
                // greater than 0 is if we already ran out of buffers previously. This means we
                // need to flush the buffers before proceeding with the sync.
                while (mNumFrameAvailable > 0) {
                    BQA_LOGD("waiting until no queued buffers");
                    mCallbackCV.wait(_lock);
                }
            }
        }

        // add to shadow queue
        mNumFrameAvailable++;
        if (waitForTransactionCallback && mNumFrameAvailable >= 2) {
            acquireAndReleaseBuffer();
        }
        ATRACE_INT(mQueuedBufferTrace.c_str(),
                   mNumFrameAvailable + mNumAcquired - mPendingRelease.size());

        BQA_LOGV("onFrameAvailable framenumber=%" PRIu64 " syncTransactionSet=%s",
                 item.mFrameNumber, boolToString(syncTransactionSet));

        if (syncTransactionSet) {
            // Add to mSyncedFrameNumbers before waiting in case any buffers are released
            // while waiting for a free buffer. The release and commit callback will try to
            // acquire buffers if there are any available, but we don't want it to acquire
            // in the case where a sync transaction wants the buffer.
            mSyncedFrameNumbers.emplace(item.mFrameNumber);
            // If there's no available buffer and we're in a sync transaction, we need to wait
            // instead of returning since we guarantee a buffer will be acquired for the sync.
            while (acquireNextBufferLocked(mSyncTransaction) == BufferQueue::NO_BUFFER_AVAILABLE) {
                BQA_LOGD("waiting for available buffer");
                mCallbackCV.wait(_lock);
            }

            // Only need a commit callback when syncing to ensure the buffer that's synced has been
            // sent to SF
            incStrong((void*)transactionCommittedCallbackThunk);
            mSyncTransaction->addTransactionCommittedCallback(transactionCommittedCallbackThunk,
                                                              static_cast<void*>(this));
            if (mAcquireSingleBuffer) {
                prevCallback = mTransactionReadyCallback;
                prevTransaction = mSyncTransaction;
                mTransactionReadyCallback = nullptr;
                mSyncTransaction = nullptr;
            }
        } else if (!waitForTransactionCallback) {
            acquireNextBufferLocked(std::nullopt);
        }
    }
    if (prevCallback) {
        prevCallback(prevTransaction);
    }
}

void BLASTBufferQueue::onFrameReplaced(const BufferItem& item) {
    BQA_LOGV("onFrameReplaced framenumber=%" PRIu64, item.mFrameNumber);
    // Do nothing since we are not storing unacquired buffer items locally.
}

void BLASTBufferQueue::onFrameDequeued(const uint64_t bufferId) {
    std::lock_guard _lock{mTimestampMutex};
    mDequeueTimestamps[bufferId] = systemTime();
};

void BLASTBufferQueue::onFrameCancelled(const uint64_t bufferId) {
    std::lock_guard _lock{mTimestampMutex};
    mDequeueTimestamps.erase(bufferId);
};

void BLASTBufferQueue::syncNextTransaction(
        std::function<void(SurfaceComposerClient::Transaction*)> callback,
        bool acquireSingleBuffer) {
    std::function<void(SurfaceComposerClient::Transaction*)> prevCallback = nullptr;
    SurfaceComposerClient::Transaction* prevTransaction = nullptr;

    {
        std::lock_guard _lock{mMutex};
        BBQ_TRACE();
        // We're about to overwrite the previous call so we should invoke that callback
        // immediately.
        if (mTransactionReadyCallback) {
            prevCallback = mTransactionReadyCallback;
            prevTransaction = mSyncTransaction;
        }

        mTransactionReadyCallback = callback;
        if (callback) {
            mSyncTransaction = new SurfaceComposerClient::Transaction();
        } else {
            mSyncTransaction = nullptr;
        }
        mAcquireSingleBuffer = mTransactionReadyCallback ? acquireSingleBuffer : true;
    }

    if (prevCallback) {
        prevCallback(prevTransaction);
    }
}

void BLASTBufferQueue::stopContinuousSyncTransaction() {
    std::function<void(SurfaceComposerClient::Transaction*)> prevCallback = nullptr;
    SurfaceComposerClient::Transaction* prevTransaction = nullptr;
    {
        std::lock_guard _lock{mMutex};
        bool invokeCallback = mTransactionReadyCallback && !mAcquireSingleBuffer;
        if (invokeCallback) {
            prevCallback = mTransactionReadyCallback;
            prevTransaction = mSyncTransaction;
        }
        mTransactionReadyCallback = nullptr;
        mSyncTransaction = nullptr;
        mAcquireSingleBuffer = true;
    }
    if (prevCallback) {
        prevCallback(prevTransaction);
    }
}

bool BLASTBufferQueue::rejectBuffer(const BufferItem& item) {
    if (item.mScalingMode != NATIVE_WINDOW_SCALING_MODE_FREEZE) {
        // Only reject buffers if scaling mode is freeze.
        return false;
    }

    ui::Size bufferSize = getBufferSize(item);
    if (mRequestedSize != mSize && mRequestedSize == bufferSize) {
        return false;
    }

    // reject buffers if the buffer size doesn't match.
    return mSize != bufferSize;
}

class BBQSurface : public Surface {
private:
    std::mutex mMutex;
    sp<BLASTBufferQueue> mBbq GUARDED_BY(mMutex);
    bool mDestroyed GUARDED_BY(mMutex) = false;

public:
    BBQSurface(const sp<IGraphicBufferProducer>& igbp, bool controlledByApp,
               const sp<IBinder>& scHandle, const sp<BLASTBufferQueue>& bbq)
          : Surface(igbp, controlledByApp, scHandle), mBbq(bbq) {}

    void allocateBuffers() override {
        uint32_t reqWidth = mReqWidth ? mReqWidth : mUserWidth;
        uint32_t reqHeight = mReqHeight ? mReqHeight : mUserHeight;
        auto gbp = getIGraphicBufferProducer();
        std::thread ([reqWidth, reqHeight, gbp=getIGraphicBufferProducer(),
                      reqFormat=mReqFormat, reqUsage=mReqUsage] () {
            gbp->allocateBuffers(reqWidth, reqHeight,
                                 reqFormat, reqUsage);

        }).detach();
    }

    status_t setFrameRate(float frameRate, int8_t compatibility,
                          int8_t changeFrameRateStrategy) override {
        std::lock_guard _lock{mMutex};
        if (mDestroyed) {
            return DEAD_OBJECT;
        }
        if (!ValidateFrameRate(frameRate, compatibility, changeFrameRateStrategy,
                               "BBQSurface::setFrameRate")) {
            return BAD_VALUE;
        }
        return mBbq->setFrameRate(frameRate, compatibility, changeFrameRateStrategy);
    }

    status_t setFrameTimelineInfo(uint64_t frameNumber,
                                  const FrameTimelineInfo& frameTimelineInfo) override {
        std::lock_guard _lock{mMutex};
        if (mDestroyed) {
            return DEAD_OBJECT;
        }
        return mBbq->setFrameTimelineInfo(frameNumber, frameTimelineInfo);
    }

    void destroy() override {
        Surface::destroy();

        std::lock_guard _lock{mMutex};
        mDestroyed = true;
        mBbq = nullptr;
    }
};

// TODO: Can we coalesce this with frame updates? Need to confirm
// no timing issues.
status_t BLASTBufferQueue::setFrameRate(float frameRate, int8_t compatibility,
                                        bool shouldBeSeamless) {
    std::lock_guard _lock{mMutex};
    SurfaceComposerClient::Transaction t;

    return t.setFrameRate(mSurfaceControl, frameRate, compatibility, shouldBeSeamless).apply();
}

status_t BLASTBufferQueue::setFrameTimelineInfo(uint64_t frameNumber,
                                                const FrameTimelineInfo& frameTimelineInfo) {
    ATRACE_FORMAT("%s(%s) frameNumber: %" PRIu64 " vsyncId: %" PRId64, __func__, mName.c_str(),
                  frameNumber, frameTimelineInfo.vsyncId);
    std::lock_guard _lock{mMutex};
    mPendingFrameTimelines.push({frameNumber, frameTimelineInfo});
    return OK;
}

void BLASTBufferQueue::setSidebandStream(const sp<NativeHandle>& stream) {
    std::lock_guard _lock{mMutex};
    SurfaceComposerClient::Transaction t;

    t.setSidebandStream(mSurfaceControl, stream).apply();
}

sp<Surface> BLASTBufferQueue::getSurface(bool includeSurfaceControlHandle) {
    std::lock_guard _lock{mMutex};
    sp<IBinder> scHandle = nullptr;
    if (includeSurfaceControlHandle && mSurfaceControl) {
        scHandle = mSurfaceControl->getHandle();
    }
    return new BBQSurface(mProducer, true, scHandle, this);
}

void BLASTBufferQueue::mergeWithNextTransaction(SurfaceComposerClient::Transaction* t,
                                                uint64_t frameNumber) {
    std::lock_guard _lock{mMutex};
    if (mLastAcquiredFrameNumber >= frameNumber) {
        // Apply the transaction since we have already acquired the desired frame.
        t->apply();
    } else {
        mPendingTransactions.emplace_back(frameNumber, *t);
        // Clear the transaction so it can't be applied elsewhere.
        t->clear();
    }
}

void BLASTBufferQueue::applyPendingTransactions(uint64_t frameNumber) {
    std::lock_guard _lock{mMutex};

    SurfaceComposerClient::Transaction t;
    mergePendingTransactions(&t, frameNumber);
    // All transactions on our apply token are one-way. See comment on mAppliedLastTransaction
    t.setApplyToken(mApplyToken).apply(false, true);
}

void BLASTBufferQueue::mergePendingTransactions(SurfaceComposerClient::Transaction* t,
                                                uint64_t frameNumber) {
    auto mergeTransaction =
            [&t, currentFrameNumber = frameNumber](
                    std::tuple<uint64_t, SurfaceComposerClient::Transaction> pendingTransaction) {
                auto& [targetFrameNumber, transaction] = pendingTransaction;
                if (currentFrameNumber < targetFrameNumber) {
                    return false;
                }
                t->merge(std::move(transaction));
                return true;
            };

    mPendingTransactions.erase(std::remove_if(mPendingTransactions.begin(),
                                              mPendingTransactions.end(), mergeTransaction),
                               mPendingTransactions.end());
}

SurfaceComposerClient::Transaction* BLASTBufferQueue::gatherPendingTransactions(
        uint64_t frameNumber) {
    std::lock_guard _lock{mMutex};
    SurfaceComposerClient::Transaction* t = new SurfaceComposerClient::Transaction();
    mergePendingTransactions(t, frameNumber);
    return t;
}

// Maintains a single worker thread per process that services a list of runnables.
class AsyncWorker : public Singleton<AsyncWorker> {
private:
    std::thread mThread;
    bool mDone = false;
    std::deque<std::function<void()>> mRunnables;
    std::mutex mMutex;
    std::condition_variable mCv;
    void run() {
        std::unique_lock<std::mutex> lock(mMutex);
        while (!mDone) {
            while (!mRunnables.empty()) {
                std::deque<std::function<void()>> runnables = std::move(mRunnables);
                mRunnables.clear();
                lock.unlock();
                // Run outside the lock since the runnable might trigger another
                // post to the async worker.
                execute(runnables);
                lock.lock();
            }
            mCv.wait(lock);
        }
    }

    void execute(std::deque<std::function<void()>>& runnables) {
        while (!runnables.empty()) {
            std::function<void()> runnable = runnables.front();
            runnables.pop_front();
            runnable();
        }
    }

public:
    AsyncWorker() : Singleton<AsyncWorker>() { mThread = std::thread(&AsyncWorker::run, this); }

    ~AsyncWorker() {
        mDone = true;
        mCv.notify_all();
        if (mThread.joinable()) {
            mThread.join();
        }
    }

    void post(std::function<void()> runnable) {
        std::unique_lock<std::mutex> lock(mMutex);
        mRunnables.emplace_back(std::move(runnable));
        mCv.notify_one();
    }
};
ANDROID_SINGLETON_STATIC_INSTANCE(AsyncWorker);

// Asynchronously calls ProducerListener functions so we can emulate one way binder calls.
class AsyncProducerListener : public BnProducerListener {
private:
    const sp<IProducerListener> mListener;

public:
    AsyncProducerListener(const sp<IProducerListener>& listener) : mListener(listener) {}

    void onBufferReleased() override {
        AsyncWorker::getInstance().post([listener = mListener]() { listener->onBufferReleased(); });
    }

    void onBuffersDiscarded(const std::vector<int32_t>& slots) override {
        AsyncWorker::getInstance().post(
                [listener = mListener, slots = slots]() { listener->onBuffersDiscarded(slots); });
    }
};

// Extends the BufferQueueProducer to create a wrapper around the listener so the listener calls
// can be non-blocking when the producer is in the client process.
class BBQBufferQueueProducer : public BufferQueueProducer {
public:
    BBQBufferQueueProducer(const sp<BufferQueueCore>& core)
          : BufferQueueProducer(core, false /* consumerIsSurfaceFlinger*/) {}

    status_t connect(const sp<IProducerListener>& listener, int api, bool producerControlledByApp,
                     QueueBufferOutput* output) override {
        if (!listener) {
            return BufferQueueProducer::connect(listener, api, producerControlledByApp, output);
        }

        return BufferQueueProducer::connect(new AsyncProducerListener(listener), api,
                                            producerControlledByApp, output);
    }

    int query(int what, int* value) override {
        if (what == NATIVE_WINDOW_QUEUES_TO_WINDOW_COMPOSER) {
            *value = 1;
            return NO_ERROR;
        }
        return BufferQueueProducer::query(what, value);
    }
};

// Similar to BufferQueue::createBufferQueue but creates an adapter specific bufferqueue producer.
// This BQP allows invoking client specified ProducerListeners and invoke them asynchronously,
// emulating one way binder call behavior. Without this, if the listener calls back into the queue,
// we can deadlock.
void BLASTBufferQueue::createBufferQueue(sp<IGraphicBufferProducer>* outProducer,
                                         sp<IGraphicBufferConsumer>* outConsumer) {
    LOG_ALWAYS_FATAL_IF(outProducer == nullptr, "BLASTBufferQueue: outProducer must not be NULL");
    LOG_ALWAYS_FATAL_IF(outConsumer == nullptr, "BLASTBufferQueue: outConsumer must not be NULL");

    sp<BufferQueueCore> core(new BufferQueueCore());
    LOG_ALWAYS_FATAL_IF(core == nullptr, "BLASTBufferQueue: failed to create BufferQueueCore");

    sp<IGraphicBufferProducer> producer(new BBQBufferQueueProducer(core));
    LOG_ALWAYS_FATAL_IF(producer == nullptr,
                        "BLASTBufferQueue: failed to create BBQBufferQueueProducer");

    sp<BufferQueueConsumer> consumer(new BufferQueueConsumer(core));
    consumer->setAllowExtraAcquire(true);
    LOG_ALWAYS_FATAL_IF(consumer == nullptr,
                        "BLASTBufferQueue: failed to create BufferQueueConsumer");

    *outProducer = producer;
    *outConsumer = consumer;
}

PixelFormat BLASTBufferQueue::convertBufferFormat(PixelFormat& format) {
    PixelFormat convertedFormat = format;
    switch (format) {
        case PIXEL_FORMAT_TRANSPARENT:
        case PIXEL_FORMAT_TRANSLUCENT:
            convertedFormat = PIXEL_FORMAT_RGBA_8888;
            break;
        case PIXEL_FORMAT_OPAQUE:
            convertedFormat = PIXEL_FORMAT_RGBX_8888;
            break;
    }
    return convertedFormat;
}

uint32_t BLASTBufferQueue::getLastTransformHint() const {
    std::lock_guard _lock{mMutex};
    if (mSurfaceControl != nullptr) {
        return mSurfaceControl->getTransformHint();
    } else {
        return 0;
    }
}

uint64_t BLASTBufferQueue::getLastAcquiredFrameNum() {
    std::lock_guard _lock{mMutex};
    return mLastAcquiredFrameNumber;
}

bool BLASTBufferQueue::isSameSurfaceControl(const sp<SurfaceControl>& surfaceControl) const {
    std::lock_guard _lock{mMutex};
    return SurfaceControl::isSameSurface(mSurfaceControl, surfaceControl);
}

void BLASTBufferQueue::setTransactionHangCallback(
        std::function<void(const std::string&)> callback) {
    std::lock_guard _lock{mMutex};
    mTransactionHangCallback = callback;
}

} // namespace android