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Commit 761286f6 authored by Glenn Kasten's avatar Glenn Kasten
Browse files

Simplify ThreadBase::exit() aka requestExitAndWait 

We can remove mExiting and use Thread::exitPending() instead.

The local sp<> on "this" in exit() is not needed, since the caller must
also hold an sp<> in order to be calling us. (Unless it was using a raw
pointer, but that would be dangerous for other reasons.)

Add comment explaining the mLock in exit().

Change-Id: I319e5107533a1a7cdbd13c292685f3e2be60f6c4
parent f4aaf1f5

services/audioflinger/AudioFlinger.cpp

+18 −8
Original line number Diff line number Diff line
@@ -998,7 +998,7 @@ AudioFlinger::ThreadBase::ThreadBase(const sp<AudioFlinger>& audioFlinger, audio 
        mChannelCount(0),

        mFrameSize(1), mFormat(AUDIO_FORMAT_INVALID),

        mParamStatus(NO_ERROR),

        mStandby(false), mId(id), mExiting(false),

        mStandby(false), mId(id),

        mDevice(device),

        mDeathRecipient(new PMDeathRecipient(this))

{
@@ -1017,17 +1017,23 @@ AudioFlinger::ThreadBase::~ThreadBase() 


void AudioFlinger::ThreadBase::exit()

{

    // keep a strong ref on ourself so that we won't get

    // destroyed in the middle of requestExitAndWait()

    sp <ThreadBase> strongMe = this;



    ALOGV("ThreadBase::exit");

    {

        // This lock prevents the following race in thread (uniprocessor for illustration):

        //  if (!exitPending()) {

        //      // context switch from here to exit()

        //      // exit() calls requestExit(), what exitPending() observes

        //      // exit() calls signal(), which is dropped since no waiters

        //      // context switch back from exit() to here

        //      mWaitWorkCV.wait(...);

        //      // now thread is hung

        //  }

        AutoMutex lock(mLock);

        mExiting = true;

        requestExit();

        mWaitWorkCV.signal();

    }

    // When Thread::requestExitAndWait is made virtual and this method is renamed to

    // "virtual status_t requestExitAndWait()", replace by "return Thread::requestExitAndWait();"

    requestExitAndWait();

}
@@ -4540,7 +4546,7 @@ status_t AudioFlinger::RecordThread::start(RecordThread::RecordTrack* recordTrac 
        ALOGV("Signal record thread");

        mWaitWorkCV.signal();

        // do not wait for mStartStopCond if exiting

        if (mExiting) {

        if (exitPending()) {

            mActiveTrack.clear();

            status = INVALID_OPERATION;

            goto startError;
@@ -4567,7 +4573,7 @@ void AudioFlinger::RecordThread::stop(RecordThread::RecordTrack* recordTrack) { 
        if (mActiveTrack != 0 && recordTrack == mActiveTrack.get()) {

            mActiveTrack->mState = TrackBase::PAUSING;

            // do not wait for mStartStopCond if exiting

            if (mExiting) {

            if (exitPending()) {

                return;

            }

            mStartStopCond.wait(mLock);
@@ -5013,6 +5019,8 @@ status_t AudioFlinger::closeOutput(audio_io_handle_t output) 
        mPlaybackThreads.removeItem(output);

    }

    thread->exit();

    // The thread entity (active unit of execution) is no longer running here,

    // but the ThreadBase container still exists.



    if (thread->type() != ThreadBase::DUPLICATING) {

        AudioStreamOut *out = thread->clearOutput();
@@ -5156,6 +5164,8 @@ status_t AudioFlinger::closeInput(audio_io_handle_t input) 
        mRecordThreads.removeItem(input);

    }

    thread->exit();

    // The thread entity (active unit of execution) is no longer running here,

    // but the ThreadBase container still exists.



    AudioStreamIn *in = thread->clearInput();

    assert(in != NULL);

services/audioflinger/AudioFlinger.h

+2 −1
Original line number Diff line number Diff line
@@ -419,6 +419,8 @@ private: 
                    audio_format_t format() const { return mFormat; }

                    size_t      frameCount() const { return mFrameCount; }

                    void        wakeUp()    { mWaitWorkCV.broadcast(); }

        // Should be "virtual status_t requestExitAndWait()" and override same

        // method in Thread, but Thread::requestExitAndWait() is not yet virtual.

                    void        exit();

        virtual     bool        checkForNewParameters_l() = 0;

        virtual     status_t    setParameters(const String8& keyValuePairs);
@@ -550,7 +552,6 @@ private: 
                    Vector<ConfigEvent>     mConfigEvents;

                    bool                    mStandby;

                    const audio_io_handle_t mId;

                    bool                    mExiting;

                    Vector< sp<EffectChain> > mEffectChains;

                    uint32_t                mDevice;    // output device for PlaybackThread

                                                        // input + output devices for RecordThread