Vsync_SurfaceFlinger

classDiagram
IBinder<|--BBinder
BBinder<|--BnInterface

IInterface<|--ISurfaceComposer

BnInterface<|--BnSurfaceComposer
ISurfaceComposer<|--BnSurfaceComposer: 泛型类型
BnSurfaceComposer<|--SurfaceFlinger

on property:vold.decrypt=trigger_restart_framework
    stop surfaceflinger
    start surfaceflinger
    # A/B update verifier that marks a successful boot.
    exec_start update_verifier
    class_start main
    class_start late_start

service surfaceflinger /system/bin/surfaceflinger
    class core animation
    user system
    group graphics drmrpc readproc
    onrestart restart zygote
    writepid /dev/stune/foreground/tasks
    socket pdx/system/vr/display/client     stream 0666 system graphics u:object_r:pdx_display_client_endpoint_socket:s0
    socket pdx/system/vr/display/manager    stream 0666 system graphics u:object_r:pdx_display_manager_endpoint_socket:s0
    socket pdx/system/vr/display/vsync      stream 0666 system graphics u:object_r:pdx_display_vsync_endpoint_socket:s0

int main(int, char**) {
  
    // When SF is launched in its own process, limit the number of
    // binder threads to 4.
    ProcessState::self()->setThreadPoolMaxThreadCount(4);
    // start the thread pool
    sp<ProcessState> ps(ProcessState::self());
    ps->startThreadPool();
  
    // instantiate surfaceflinger
    sp<SurfaceFlinger> flinger = new SurfaceFlinger();
    setpriority(PRIO_PROCESS, 0, PRIORITY_URGENT_DISPLAY);
    set_sched_policy(0, SP_FOREGROUND);
  
    // initialize before clients can connect
    flinger->init();
  
    // publish surface flinger
    sp<IServiceManager> sm(defaultServiceManager());
    sm->addService(String16(SurfaceFlinger::getServiceName()), flinger, false,
                   IServiceManager::DUMP_FLAG_PRIORITY_CRITICAL);
  
    // run surface flinger in this thread
    flinger->run();
    return 0;
}

class SurfaceFlinger : public BnSurfaceComposer,
                       public PriorityDumper,
                       private IBinder::DeathRecipient,
                       private HWC2::ComposerCallback
{
    // these are thread safe
    mutable std::unique_ptr<MessageQueue> mEventQueue{std::make_unique<impl::MessageQueue>()};     
                         
    VSyncModulator mVsyncModulator;    

    DispSync mPrimaryDispSync;

    using CreateBufferQueueFunction =
            std::function<void(sp<IGraphicBufferProducer>* /* outProducer */,
                               sp<IGraphicBufferConsumer>* /* outConsumer */,
                               bool /* consumerIsSurfaceFlinger */)>;
    CreateBufferQueueFunction mCreateBufferQueue;
                           
    using CreateNativeWindowSurfaceFunction =
            std::function<std::unique_ptr<NativeWindowSurface>(const sp<IGraphicBufferProducer>&)>;
    CreateNativeWindowSurfaceFunction mCreateNativeWindowSurface;
}

SurfaceFlinger::SurfaceFlinger(SurfaceFlinger::SkipInitializationTag)
      : BnSurfaceComposer(),
        Display(false),
        ......
        mMainThreadId(std::this_thread::get_id()),
        mCreateBufferQueue(&BufferQueue::createBufferQueue),
        mCreateNativeWindowSurface(&impl::NativeWindowSurface::create) {}

void SurfaceFlinger::onFirstRef()
{
    mEventQueue->init(this);
}

void SurfaceFlinger::init() {
   // start the EventThread
    mEventThreadSource =
            std::make_unique<DispSyncSource>(&mPrimaryDispSync, SurfaceFlinger::vsyncPhaseOffsetNs,
                                             true, "app");
    mEventThread = std::make_unique<impl::EventThread>(mEventThreadSource.get(),
                                                       [this]() { resyncWithRateLimit(); },
                                                       impl::EventThread::InterceptVSyncsCallback(),
                                                       "appEventThread");
    mSfEventThreadSource =
            std::make_unique<DispSyncSource>(&mPrimaryDispSync,
                                             SurfaceFlinger::sfVsyncPhaseOffsetNs, true, "sf");

    mSFEventThread =
            std::make_unique<impl::EventThread>(mSfEventThreadSource.get(),
                                                [this]() { resyncWithRateLimit(); },
                                                [this](nsecs_t timestamp) {
                                                    mInterceptor->saveVSyncEvent(timestamp);
    mEventQueue->setEventThread(mSFEventThread.get());
    mVsyncModulator.setEventThread(mSFEventThread.get());
                                                    
    // Get a RenderEngine for the given display / config (can't fail)
    getBE().mRenderEngine =
            RE::impl::RenderEngine::create(HAL_PIXEL_FORMAT_RGBA_8888,
                                           hasWideColorDisplay
                                                   ? RE::RenderEngine::WIDE_COLOR_SUPPORT
                                                   : 0);

    getBE().mHwc.reset(
            new HWComposer(std::make_unique<Hwc2::impl::Composer>(getBE().mHwcServiceName)));
    getBE().mHwc->registerCallback(this, getBE().mComposerSequenceId);
                                                    
    mEventControlThread = std::make_unique<impl::EventControlThread>(
            [this](bool enabled) { setVsyncEnabled(HWC_DISPLAY_PRIMARY, enabled); });
                                                    
     // set initial conditions (e.g. unblank default device)
    initializeDisplays();
}

void SurfaceFlinger::onVsyncReceived(int32_t sequenceId,
        hwc2_display_t displayId, int64_t timestamp) {
    Mutex::Autolock lock(mStateLock);
    // Ignore any vsyncs from a previous hardware composer.
    if (sequenceId != getBE().mComposerSequenceId) {
        return;
    }

    int32_t type;
    if (!getBE().mHwc->onVsync(displayId, timestamp, &type)) {
        return;
    }

    bool needsHwVsync = false;

    { // Scope for the lock
        Mutex::Autolock _l(mHWVsyncLock);
        if (type == DisplayDevice::DISPLAY_PRIMARY && mPrimaryHWVsyncEnabled) {
            needsHwVsync = mPrimaryDispSync.addResyncSample(timestamp);
        }
    }

    if (needsHwVsync) {
        enableHardwareVsync();
    } else {
        disableHardwareVsync(false);
    }
}

void SurfaceFlinger::disableHardwareVsync(bool makeUnavailable) {
    Mutex::Autolock _l(mHWVsyncLock);
    if (mPrimaryHWVsyncEnabled) {
        //eventControl(HWC_DISPLAY_PRIMARY, SurfaceFlinger::EVENT_VSYNC, false);
        mEventControlThread->setVsyncEnabled(false);
        mPrimaryDispSync.endResync();
        mPrimaryHWVsyncEnabled = false;
    }
    if (makeUnavailable) {
        mHWVsyncAvailable = false;
    }
}

void SurfaceFlinger::run() {
    do {
        waitForEvent();
    } while (true);
}

void SurfaceFlinger::waitForEvent() {
    mEventQueue->waitMessage();
}

void SurfaceFlinger::onMessageReceived(int32_t what) {
    switch (what) {
        case MessageQueue::INVALIDATE: {
            bool refreshNeeded = handleMessageTransaction();
            refreshNeeded |= handleMessageInvalidate();
            refreshNeeded |= mRepaintEverything;
            if (refreshNeeded) {
                // Signal a refresh if a transaction modified the window state,
                // a new buffer was latched, or if HWC has requested a full
                // repaint
                signalRefresh();//call handleMessageRefresh()
            }
            break;
        }
        case MessageQueue::REFRESH: {
            handleMessageRefresh();
            break;
        }
    }
}

void SurfaceFlinger::handleMessageRefresh() {
    ATRACE_CALL();

    mRefreshPending = false;

    nsecs_t refreshStartTime = systemTime(SYSTEM_TIME_MONOTONIC);

    preComposition(refreshStartTime);
    rebuildLayerStacks();
    setUpHWComposer();
    doDebugFlashRegions();
    doTracing("handleRefresh");
    logLayerStats();
    doComposition();
    postComposition(refreshStartTime);

    mPreviousPresentFence = getBE().mHwc->getPresentFence(HWC_DISPLAY_PRIMARY);

    mHadClientComposition = false;
    for (size_t displayId = 0; displayId < mDisplays.size(); ++displayId) {
        const sp<DisplayDevice>& displayDevice = mDisplays[displayId];
        mHadClientComposition = mHadClientComposition ||
                getBE().mHwc->hasClientComposition(displayDevice->getHwcDisplayId());
    }
    mVsyncModulator.onRefreshed(mHadClientComposition);

    mLayersWithQueuedFrames.clear();
}

sp<IDisplayEventConnection> SurfaceFlinger::createDisplayEventConnection(
        ISurfaceComposer::VsyncSource vsyncSource) {
    if (vsyncSource == eVsyncSourceSurfaceFlinger) {
        return mSFEventThread->createEventConnection();
    } else {
        return mEventThread->createEventConnection();
    }
}

void SurfaceFlinger::resyncWithRateLimit() {
    static constexpr nsecs_t kIgnoreDelay = ms2ns(500);

    // No explicit locking is needed here since EventThread holds a lock while calling this method
    static nsecs_t sLastResyncAttempted = 0;
    const nsecs_t now = systemTime();
    if (now - sLastResyncAttempted > kIgnoreDelay) {
        resyncToHardwareVsync(false);
    }
    sLastResyncAttempted = now;
}

void SurfaceFlinger::resyncToHardwareVsync(bool makeAvailable) {
    Mutex::Autolock _l(mHWVsyncLock);

    if (makeAvailable) {
        mHWVsyncAvailable = true;
    } else if (!mHWVsyncAvailable) {
        // Hardware vsync is not currently available, so abort the resync
        // attempt for now
        return;
    }

    const auto& activeConfig = getBE().mHwc->getActiveConfig(HWC_DISPLAY_PRIMARY);
    const nsecs_t period = activeConfig->getVsyncPeriod();

    mPrimaryDispSync.reset();
    mPrimaryDispSync.setPeriod(period);

    if (!mPrimaryHWVsyncEnabled) {
        mPrimaryDispSync.beginResync();
        //eventControl(HWC_DISPLAY_PRIMARY, SurfaceFlinger::EVENT_VSYNC, true);
        mEventControlThread->setVsyncEnabled(true);
        mPrimaryHWVsyncEnabled = true;
    }
}

void SurfaceFlinger::setVsyncEnabled(int disp, int enabled) {
    getHwComposer().setVsyncEnabled(disp,
            enabled ? HWC2::Vsync::Enable : HWC2::Vsync::Disable);
}

    enum VsyncSource {
        eVsyncSourceApp = 0,
        eVsyncSourceSurfaceFlinger = 1
    };

:IComposerCallback
ComposerCallback* mCallback;

Return<void> onVsync(Hwc2::Display display, int64_t timestamp) override
{
mCallback->onVsyncReceived(mSequenceId, display, timestamp);
return Void();
}

    DispSync* mDispSync;

    Mutex mCallbackMutex; // Protects the following
    VSyncSource::Callback* mCallback = nullptr;

    virtual void onDispSyncEvent(nsecs_t when) {
        VSyncSource::Callback* callback;
        {
            Mutex::Autolock lock(mCallbackMutex);
            callback = mCallback;

            if (mTraceVsync) {
                mValue = (mValue + 1) % 2;
                ATRACE_INT(mVsyncEventLabel.string(), mValue);
            }
        }

        if (callback != nullptr) {
            callback->onVSyncEvent(when);
        }
    }

class EventThread : public android::EventThread, private VSyncSource::Callback {
    class Connection : public BnDisplayEventConnection {
    public:
        explicit Connection(EventThread* eventThread);
        virtual ~Connection();

        virtual status_t postEvent(const DisplayEventReceiver::Event& event);

        // count >= 1 : continuous event. count is the vsync rate
        // count == 0 : one-shot event that has not fired
        // count ==-1 : one-shot event that fired this round / disabled
        int32_t count;

    private:
        virtual void onFirstRef();
        status_t stealReceiveChannel(gui::BitTube* outChannel) override;
        status_t setVsyncRate(uint32_t count) override;
        void requestNextVsync() override; // asynchronous
        EventThread* const mEventThread;
        gui::BitTube mChannel;
    };

EventThread::EventThread(VSyncSource* src, ResyncWithRateLimitCallback resyncWithRateLimitCallback,
                         InterceptVSyncsCallback interceptVSyncsCallback, const char* threadName)
      : mVSyncSource(src),
        mResyncWithRateLimitCallback(resyncWithRateLimitCallback),
        mInterceptVSyncsCallback(interceptVSyncsCallback) {
    for (auto& event : mVSyncEvent) {
        event.header.type = DisplayEventReceiver::DISPLAY_EVENT_VSYNC;
        event.header.id = 0;
        event.header.timestamp = 0;
        event.vsync.count = 0;
    }

    mThread = std::thread(&EventThread::threadMain, this);

    pthread_setname_np(mThread.native_handle(), threadName);

    pid_t tid = pthread_gettid_np(mThread.native_handle());

    // Use SCHED_FIFO to minimize jitter
    constexpr int EVENT_THREAD_PRIORITY = 2;
    struct sched_param param = {0};
    param.sched_priority = EVENT_THREAD_PRIORITY;
    if (pthread_setschedparam(mThread.native_handle(), SCHED_FIFO, &param) != 0) {
        ALOGE("Couldn't set SCHED_FIFO for EventThread");
    }

    set_sched_policy(tid, SP_FOREGROUND);
}

void EventThread::threadMain() NO_THREAD_SAFETY_ANALYSIS {
    std::unique_lock<std::mutex> lock(mMutex);
    while (mKeepRunning) {
        DisplayEventReceiver::Event event;
        Vector<sp<EventThread::Connection> > signalConnections;
        signalConnections = waitForEventLocked(&lock, &event);

        // dispatch events to listeners...
        const size_t count = signalConnections.size();
        for (size_t i = 0; i < count; i++) {
            const sp<Connection>& conn(signalConnections[i]);
            // now see if we still need to report this event
            status_t err = conn->postEvent(event);
        }
    }
}

// This will return when (1) a vsync event has been received, and (2) there was
// at least one connection interested in receiving it when we started waiting.
Vector<sp<EventThread::Connection> > EventThread::waitForEventLocked(
        std::unique_lock<std::mutex>* lock, DisplayEventReceiver::Event* event) {
    
   ......
          if (!timestamp && !eventPending) {
            // wait for something to happen
            if (waitForVSync) {
                // This is where we spend most of our time, waiting
                // for vsync events and new client registrations.
                //
                // If the screen is off, we can't use h/w vsync, so we
                // use a 16ms timeout instead.  It doesn't need to be
                // precise, we just need to keep feeding our clients.
                //
                // We don't want to stall if there's a driver bug, so we
                // use a (long) timeout when waiting for h/w vsync, and
                // generate fake events when necessary.
                bool softwareSync = mUseSoftwareVSync;
                auto timeout = softwareSync ? 16ms : 1000ms;
                if (mCondition.wait_for(*lock, timeout) == std::cv_status::timeout) {
                    if (!softwareSync) {
                        ALOGW("Timed out waiting for hw vsync; faking it");
                    }
                    // FIXME: how do we decide which display id the fake
                    // vsync came from ?
                    mVSyncEvent[0].header.type = DisplayEventReceiver::DISPLAY_EVENT_VSYNC;
                    mVSyncEvent[0].header.id = DisplayDevice::DISPLAY_PRIMARY;
                    mVSyncEvent[0].header.timestamp = systemTime(SYSTEM_TIME_MONOTONIC);
                    mVSyncEvent[0].vsync.count++;
                }
            } else {
                // Nobody is interested in vsync, so we just want to sleep.
                // h/w vsync should be disabled, so this will wait until we
                // get a new connection, or an existing connection becomes
                // interested in receiving vsync again.
                mCondition.wait(*lock);
            }
              
    // here we're guaranteed to have a timestamp and some connections to signal
    // (The connections might have dropped out of mDisplayEventConnections
    // while we were asleep, but we'll still have strong references to them.)
    return signalConnections;
}

void EventThread::onVSyncEvent(nsecs_t timestamp) {
    std::lock_guard<std::mutex> lock(mMutex);
    mVSyncEvent[0].header.type = DisplayEventReceiver::DISPLAY_EVENT_VSYNC;
    mVSyncEvent[0].header.id = 0;
    mVSyncEvent[0].header.timestamp = timestamp;
    mVSyncEvent[0].vsync.count++;
    mCondition.notify_all();//唤醒EventThread线程
}

status_t EventThread::Connection::postEvent(const DisplayEventReceiver::Event& event) {
    ssize_t size = DisplayEventReceiver::sendEvents(&mChannel, &event, 1);
    return size < 0 ? status_t(size) : status_t(NO_ERROR);
}

sp<BnDisplayEventConnection> EventThread::createEventConnection() const {
    return new Connection(const_cast<EventThread*>(this));
}

    /*
     * stealReceiveChannel() returns a BitTube to receive events from. Only the receive file
     * descriptor of outChannel will be initialized, and this effectively "steals" the receive
     * channel from the remote end (such that the remote end can only use its send channel).
     */
status_t EventThread::Connection::stealReceiveChannel(gui::BitTube* outChannel) {
    outChannel->setReceiveFd(mChannel.moveReceiveFd());
    return NO_ERROR;
}

void EventThread::Connection::requestNextVsync() {
    mEventThread->requestNextVsync(this);
}

void EventThread::requestNextVsync(const sp<EventThread::Connection>& connection) {
    std::lock_guard<std::mutex> lock(mMutex);

    if (mResyncWithRateLimitCallback) {
        mResyncWithRateLimitCallback();//callback resyncWithRateLimit in SurfaceFlinger
    }

    if (connection->count < 0) {
        connection->count = 0;
        mCondition.notify_all();
    }
}

void EventControlThread::setVsyncEnabled(bool enabled) {
    std::lock_guard<std::mutex> lock(mMutex);
    mVsyncEnabled = enabled;
    mCondition.notify_all();
}

// Unfortunately std::unique_lock gives warnings with -Wthread-safety
void EventControlThread::threadMain() NO_THREAD_SAFETY_ANALYSIS {
    auto keepRunning = true;
    auto currentVsyncEnabled = false;

    while (keepRunning) {
        mSetVSyncEnabled(currentVsyncEnabled);

        std::unique_lock<std::mutex> lock(mMutex);
        mCondition.wait(lock, [this, currentVsyncEnabled, keepRunning]() NO_THREAD_SAFETY_ANALYSIS {
            return currentVsyncEnabled != mVsyncEnabled || keepRunning != mKeepRunning;
        });
        currentVsyncEnabled = mVsyncEnabled;
        keepRunning = mKeepRunning;
    }
}

ssize_t DisplayEventReceiver::sendEvents(gui::BitTube* dataChannel,
        Event const* events, size_t count)
{
    return gui::BitTube::sendObjects(dataChannel, events, count);
}

// Socket buffer size.  The default is typically about 128KB, which is much larger than we really
// need. So we make it smaller.
static const size_t DEFAULT_SOCKET_BUFFER_SIZE = 4 * 1024;

BitTube::BitTube(size_t bufsize) {
    init(bufsize, bufsize);
}

void BitTube::init(size_t rcvbuf, size_t sndbuf) {
    int sockets[2];
    if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, sockets) == 0) {
        size_t size = DEFAULT_SOCKET_BUFFER_SIZE;
        setsockopt(sockets[0], SOL_SOCKET, SO_RCVBUF, &rcvbuf, sizeof(rcvbuf));
        setsockopt(sockets[1], SOL_SOCKET, SO_SNDBUF, &sndbuf, sizeof(sndbuf));
        // since we don't use the "return channel", we keep it small...
        setsockopt(sockets[0], SOL_SOCKET, SO_SNDBUF, &size, sizeof(size));
        setsockopt(sockets[1], SOL_SOCKET, SO_RCVBUF, &size, sizeof(size));
        fcntl(sockets[0], F_SETFL, O_NONBLOCK);
        fcntl(sockets[1], F_SETFL, O_NONBLOCK);
        mReceiveFd.reset(sockets[0]);
        mSendFd.reset(sockets[1]);
    } else {
        mReceiveFd.reset();
        ALOGE("BitTube: pipe creation failed (%s)", strerror(errno));
    }
}

ssize_t BitTube::sendObjects(BitTube* tube, void const* events, size_t count, size_t objSize) {
    const char* vaddr = reinterpret_cast<const char*>(events);
    ssize_t size = tube->write(vaddr, count * objSize);

    // ALOGE_IF(size<0, "error %d sending %d events", size, count);
    return size < 0 ? size : size / static_cast<ssize_t>(objSize);
}

ssize_t BitTube::write(void const* vaddr, size_t size) {
    ssize_t err, len;
    do {
        len = ::send(mSendFd, vaddr, size, MSG_DONTWAIT | MSG_NOSIGNAL);
        // cannot return less than size, since we're using SOCK_SEQPACKET
        err = len < 0 ? errno : 0;
    } while (err == EINTR);
    return err == 0 ? len : -err;
}

ssize_t BitTube::recvObjects(BitTube* tube, void* events, size_t count, size_t objSize) {
    char* vaddr = reinterpret_cast<char*>(events);
    ssize_t size = tube->read(vaddr, count * objSize);

    // ALOGE_IF(size<0, "error %d receiving %d events", size, count);
    return size < 0 ? size : size / static_cast<ssize_t>(objSize);
}

    // mThread is the thread from which all the callbacks are called.
    sp<DispSyncThread> mThread;

void DispSync::init(bool hasSyncFramework, int64_t dispSyncPresentTimeOffset) {
    mThread->run("DispSync", PRIORITY_URGENT_DISPLAY + PRIORITY_MORE_FAVORABLE);

    reset();
    beginResync();
}

bool DispSync::addResyncSample(nsecs_t timestamp) {
       updateModelLocked();
}

void DispSync::updateModelLocked() {
      mThread->updateModel(mPeriod, mPhase, mReferenceTime);
}

class DispSyncThread : public Thread {
    Vector<EventListener> mEventListeners;
}

    virtual bool threadLoop() {
        status_t err;
        nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);

        while (true) {
                targetTime = computeNextEventTimeLocked(now);

                bool isWakeup = false;

                if (now < targetTime) {
                    if (kTraceDetailedInfo) ATRACE_NAME("DispSync waiting");

                    if (targetTime == INT64_MAX) {
                        ALOGV("[%s] Waiting forever", mName);
                        err = mCond.wait(mMutex);
                    } else {
                        ALOGV("[%s] Waiting until %" PRId64, mName, ns2us(targetTime));
                        err = mCond.waitRelative(mMutex, targetTime - now);
                    }
                }
            
               callbackInvocations = gatherCallbackInvocationsLocked(now);
               if (callbackInvocations.size() > 0) {
                    fireCallbackInvocations(callbackInvocations);
               }
        }
    }

    Vector<CallbackInvocation> gatherCallbackInvocationsLocked(nsecs_t now) {
        Vector<CallbackInvocation> callbackInvocations;
        nsecs_t onePeriodAgo = now - mPeriod;

        for (size_t i = 0; i < mEventListeners.size(); i++) {
            nsecs_t t = computeListenerNextEventTimeLocked(mEventListeners[i], onePeriodAgo);
            if (t < now) {
                CallbackInvocation ci;
                ci.mCallback = mEventListeners[i].mCallback;
                ci.mEventTime = t;
                callbackInvocations.push(ci);
                mEventListeners.editItemAt(i).mLastEventTime = t;
            }
        }
        return callbackInvocations;
    }

    void fireCallbackInvocations(const Vector<CallbackInvocation>& callbacks) {
        for (size_t i = 0; i < callbacks.size(); i++) {
            callbacks[i].mCallback->onDispSyncEvent(callbacks[i].mEventTime);
        }
    }

    void updateModel(nsecs_t period, nsecs_t phase, nsecs_t referenceTime) {
        Mutex::Autolock lock(mMutex);
        mPeriod = period;
        mPhase = phase;
        mReferenceTime = referenceTime;

        mCond.signal();
    }

namespace impl {

class MessageQueue final : public android::MessageQueue {
    class Handler : public MessageHandler {
        enum { eventMaskInvalidate = 0x1, eventMaskRefresh = 0x2, eventMaskTransaction = 0x4 };
        MessageQueue& mQueue;
        int32_t mEventMask;

    public:
        explicit Handler(MessageQueue& queue) : mQueue(queue), mEventMask(0) {}
        virtual void handleMessage(const Message& message);
        void dispatchRefresh();
        void dispatchInvalidate();
    };

    friend class Handler;

    sp<SurfaceFlinger> mFlinger;
    sp<Looper> mLooper;
    android::EventThread* mEventThread;
    sp<IDisplayEventConnection> mEvents;
    gui::BitTube mEventTube;
    sp<Handler> mHandler;
}

void MessageQueue::init(const sp<SurfaceFlinger>& flinger) {
    mFlinger = flinger;
    mLooper = new Looper(true);//system/core/include/utils/Looper.h
    mHandler = new Handler(*this);
}

void MessageQueue::setEventThread(android::EventThread* eventThread) {
    if (mEventThread == eventThread) {
        return;
    }

    if (mEventTube.getFd() >= 0) {
        mLooper->removeFd(mEventTube.getFd());
    }

    mEventThread = eventThread;
    mEvents = eventThread->createEventConnection();
    mEvents->stealReceiveChannel(&mEventTube);
    mLooper->addFd(mEventTube.getFd(), 0, Looper::EVENT_INPUT, MessageQueue::cb_eventReceiver,
                   this);
}

void MessageQueue::waitMessage() {
    do {
        IPCThreadState::self()->flushCommands();
        int32_t ret = mLooper->pollOnce(-1);
        switch (ret) {
            case Looper::POLL_WAKE:
            case Looper::POLL_CALLBACK:
                continue;
            case Looper::POLL_ERROR:
                ALOGE("Looper::POLL_ERROR");
                continue;
            case Looper::POLL_TIMEOUT:
                // timeout (should not happen)
                continue;
            default:
                // should not happen
                ALOGE("Looper::pollOnce() returned unknown status %d", ret);
                continue;
        }
    } while (true);
}

int MessageQueue::cb_eventReceiver(int fd, int events, void* data) {
    MessageQueue* queue = reinterpret_cast<MessageQueue*>(data);
    return queue->eventReceiver(fd, events);
}

int MessageQueue::eventReceiver(int /*fd*/, int /*events*/) {
    ssize_t n;
    DisplayEventReceiver::Event buffer[8];
    while ((n = DisplayEventReceiver::getEvents(&mEventTube, buffer, 8)) > 0) {
        for (int i = 0; i < n; i++) {
            if (buffer[i].header.type == DisplayEventReceiver::DISPLAY_EVENT_VSYNC) {
                mHandler->dispatchInvalidate();
                break;
            }
        }
    }
    return 1;
}

void MessageQueue::Handler::dispatchInvalidate() {
    if ((android_atomic_or(eventMaskInvalidate, &mEventMask) & eventMaskInvalidate) == 0) {
        mQueue.mLooper->sendMessage(this, Message(MessageQueue::INVALIDATE));
    }
}

void MessageQueue::Handler::handleMessage(const Message& message) {
    switch (message.what) {
        case INVALIDATE:
            android_atomic_and(~eventMaskInvalidate, &mEventMask);
            mQueue.mFlinger->onMessageReceived(message.what);
            break;
        case REFRESH:
            android_atomic_and(~eventMaskRefresh, &mEventMask);
            mQueue.mFlinger->onMessageReceived(message.what);
            break;
    }
}

// Implement this interface to receive hardware composer events.
//
// These callback functions will generally be called on a hwbinder thread, but
// when first registering the callback the onHotplugReceived() function will
// immediately be called on the thread calling registerCallback().
//
// All calls receive a sequenceId, which will be the value that was supplied to
// HWC2::Device::registerCallback(). It's used to help differentiate callbacks
// from different hardware composer instances.
class ComposerCallback {
 public:
    virtual void onHotplugReceived(int32_t sequenceId, hwc2_display_t display,
                                   Connection connection) = 0;
    virtual void onRefreshReceived(int32_t sequenceId,
                                   hwc2_display_t display) = 0;
    virtual void onVsyncReceived(int32_t sequenceId, hwc2_display_t display,
                                 int64_t timestamp) = 0;
    virtual ~ComposerCallback() = default;
};

virtual status_t queueBuffer(int buf,
        const QueueBufferInput& input, QueueBufferOutput* output) {
    Parcel data, reply;

    data.writeInterfaceToken(IGraphicBufferProducer::getInterfaceDescriptor());
    data.writeInt32(buf);
    data.write(input);

    status_t result = remote()->transact(QUEUE_BUFFER, data, &reply);

    return result;
}

status_t BnGraphicBufferProducer::onTransact(
    uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags)
{
    switch(code) {    
            case QUEUE_BUFFER: {
            CHECK_INTERFACE(IGraphicBufferProducer, data, reply);

            int buf = data.readInt32();
            QueueBufferInput input(data);
            QueueBufferOutput output;
            status_t result = queueBuffer(buf, input, &output);
            reply->write(output);
            reply->writeInt32(result);

            return NO_ERROR;
        }

│79      status_t MonitoredProducer::queueBuffer(int slot, const QueueBufferInput& input,                                             
   │80              QueueBufferOutput* output) {                                                                                         
  >│81          return mProducer->queueBuffer(slot, input, output);                                                                      
   │82      }                                                                                                                            
   │83 

│750     status_t BufferQueueProducer::queueBuffer(int slot,                                                                          
   │751             const QueueBufferInput &input, QueueBufferOutput *output) {  
    
      >│977                 frameAvailableListener->onFrameAvailable(item);                                                                  

   │46      void BufferQueue::ProxyConsumerListener::onFrameAvailable(                                                                   
   │47              const BufferItem& item) {                                                                                            
   │48          sp<ConsumerListener> listener(mConsumerListener.promote());                                                              
   │49          if (listener != NULL) {                                                                                                  
  >│50              listener->onFrameAvailable(item);                                                                                    
   │51          }                                                                                                                        
   │52      } 

   │104     void ConsumerBase::onFrameAvailable(const BufferItem& item) {                                                                
   │105         CB_LOGV("onFrameAvailable");                                                                                             
   │106                                                                                                                                  
   │107         sp<FrameAvailableListener> listener;                                                                                     
   │108         { // scope for the lock                                                                                                  
   │109             Mutex::Autolock lock(mFrameAvailableMutex);                                                                          
   │110             listener = mFrameAvailableListener.promote();                                                                        
   │111         }                                                                                                                        
   │112                                                                                                                                  
   │113         if (listener != NULL) {                                                                                                  
   │114             CB_LOGV("actually calling onFrameAvailable");                                                                        
  >│115             listener->onFrameAvailable(item);                                                                                    
   │116         }                                                                                                                        
   │117     } 

   │723     // ---------------------------------------------------------------------------                                               
   │724     // Interface implementation for SurfaceFlingerConsumer::ContentsChangedListener                                              
   │725     // ---------------------------------------------------------------------------                                               
   │726                                                                                                                                  
   │727     void BufferLayer::onFrameAvailable(const BufferItem& item) {                                                                 
   │728         // Add this buffer from our internal queue tracker                                                                       
   │729         { // Autolock scope                                                                                                      
B+>│730             Mutex::Autolock lock(mQueueItemLock);