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Commit 717bc28f authored by Eric Laurent's avatar Eric Laurent
Browse files

audio flinger: handle race condition in AudioRecord creation 

A rare race condition can cause a failure to create an AudioRecord if
two creation requests are processed concurrently and thread preemption happens
at a specific time within the sequence between audioflinger and
audio policy manager.

This CL implements a retry mechanism on client side when this particular failure
is detected.

Bug: 161656190
Test: Regression tests for audio capture use cases.
Test: CTS tests for AudiRecord
Change-Id: I155ee4899baeec21e10a1141cb9e323cbc8aa23b
(cherry picked from commit d52a28ca)
parent 0b3f2540

media/libaudioclient/AudioRecord.cpp

+19 −8
Original line number Diff line number Diff line
@@ -742,6 +742,8 @@ status_t AudioRecord::createRecord_l(const Modulo<uint32_t> &epoch, const String 
    void *iMemPointer;

    audio_track_cblk_t* cblk;

    status_t status;

    static const int32_t kMaxCreateAttempts = 3;

    int32_t remainingAttempts = kMaxCreateAttempts;



    if (audioFlinger == 0) {

        ALOGE("%s(%d): Could not get audioflinger", __func__, mPortId);
@@ -803,15 +805,24 @@ status_t AudioRecord::createRecord_l(const Modulo<uint32_t> &epoch, const String 
    input.sessionId = mSessionId;

    originalSessionId = mSessionId;



    record = audioFlinger->createRecord(input,

                                                              output,

                                                              &status);



    if (status != NO_ERROR) {

    do {

        record = audioFlinger->createRecord(input, output, &status);

        if (status == NO_ERROR) {

            break;

        }

        if (status != FAILED_TRANSACTION || --remainingAttempts <= 0) {

            ALOGE("%s(%d): AudioFlinger could not create record track, status: %d",

                  __func__, mPortId, status);

            goto exit;

        }

        // FAILED_TRANSACTION happens under very specific conditions causing a state mismatch

        // between audio policy manager and audio flinger during the input stream open sequence

        // and can be recovered by retrying.

        // Leave time for race condition to clear before retrying and randomize delay

        // to reduce the probability of concurrent retries in locked steps.

        usleep((20 + rand() % 30) * 10000);

    } while (1);



    ALOG_ASSERT(record != 0);



    // AudioFlinger now owns the reference to the I/O handle,

services/audioflinger/AudioFlinger.cpp

+2 −2
Original line number Diff line number Diff line
@@ -2068,8 +2068,8 @@ sp<media::IAudioRecord> AudioFlinger::createRecord(const CreateRecordInput& inpu 
        Mutex::Autolock _l(mLock);

        RecordThread *thread = checkRecordThread_l(output.inputId);

        if (thread == NULL) {

            ALOGE("createRecord() checkRecordThread_l failed, input handle %d", output.inputId);

            lStatus = BAD_VALUE;

            ALOGW("createRecord() checkRecordThread_l failed, input handle %d", output.inputId);

            lStatus = FAILED_TRANSACTION;

            goto Exit;

        }

services/audioflinger/Threads.cpp

+4 −2
Original line number Diff line number Diff line
@@ -7869,7 +7869,8 @@ status_t AudioFlinger::RecordThread::start(RecordThread::RecordTrack* recordTrac 
        AutoMutex lock(mLock);

        if (recordTrack->isInvalid()) {

            recordTrack->clearSyncStartEvent();

            return INVALID_OPERATION;

            ALOGW("%s track %d: invalidated before startInput", __func__, recordTrack->portId());

            return DEAD_OBJECT;

        }

        if (mActiveTracks.indexOf(recordTrack) >= 0) {

            if (recordTrack->mState == TrackBase::PAUSING) {
@@ -7899,7 +7900,8 @@ status_t AudioFlinger::RecordThread::start(RecordThread::RecordTrack* recordTrac 
                    recordTrack->mState = TrackBase::STARTING_2;

                    // STARTING_2 forces destroy to call stopInput.

                }

                return INVALID_OPERATION;

                ALOGW("%s track %d: invalidated after startInput", __func__, recordTrack->portId());

                return DEAD_OBJECT;

            }

            if (recordTrack->mState != TrackBase::STARTING_1) {

                ALOGW("%s(%d): unsynchronized mState:%d change",

services/audioflinger/Tracks.cpp

+2 −1
Original line number Diff line number Diff line
@@ -2207,7 +2207,8 @@ status_t AudioFlinger::RecordThread::RecordTrack::start(AudioSystem::sync_event_ 
        RecordThread *recordThread = (RecordThread *)thread.get();

        return recordThread->start(this, event, triggerSession);

    } else {

        return BAD_VALUE;

        ALOGW("%s track %d: thread was destroyed", __func__, portId());

        return DEAD_OBJECT;

    }

}

services/audiopolicy/managerdefault/AudioPolicyManager.cpp

+1 −1
Original line number Diff line number Diff line
@@ -2256,7 +2256,7 @@ status_t AudioPolicyManager::startInput(audio_port_handle_t portId) 
    sp<AudioInputDescriptor> inputDesc = mInputs.getInputForClient(portId);

    if (inputDesc == 0) {

        ALOGW("%s no input for client %d", __FUNCTION__, portId);

        return BAD_VALUE;

        return DEAD_OBJECT;

    }

    audio_io_handle_t input = inputDesc->mIoHandle;

    sp<RecordClientDescriptor> client = inputDesc->getClient(portId);