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Commit 98c92599 authored by Eric Laurent's avatar Eric Laurent
Browse files

Fix issue 3007862 

Removed a cross deadlock condition between audioflinger and audio policy
service mutexes.
Audioflinger::createEffect() locks audioflinger mutex and then calls
AudioSystem::getOutputForEffect() which ends up in
AudioPolicyService::getOutputForEffect() which locks audio policy service
mutex. If at the same time, the command thread in audio policy service is
processing a command(set volume, set route...), the mutex is locked and the
command will call one audioflinger method which in turn will attempt to
lock audioflinger mutex.
The fix consists in releasing audioflinger mutex before calling
getOutputForEffect().

Change-Id: Id44e7feb36e0a295731f6aa97cf32d022edd34d0
parent 287952c3

services/audioflinger/AudioFlinger.cpp

+49 −40
Original line number Diff line number Diff line
@@ -4653,9 +4653,6 @@ sp<IEffect> AudioFlinger::createEffect(pid_t pid, 
        goto Exit;

    }



    {

        Mutex::Autolock _l(mLock);



    // check audio settings permission for global effects

    if (sessionId == AudioSystem::SESSION_OUTPUT_MIX && !settingsAllowed()) {

        lStatus = PERMISSION_DENIED;
@@ -4677,6 +4674,24 @@ sp<IEffect> AudioFlinger::createEffect(pid_t pid, 
        goto Exit;

    }



    if (output == 0) {

        if (sessionId == AudioSystem::SESSION_OUTPUT_STAGE) {

            // output must be specified by AudioPolicyManager when using session

            // AudioSystem::SESSION_OUTPUT_STAGE

            lStatus = BAD_VALUE;

            goto Exit;

        } else if (sessionId == AudioSystem::SESSION_OUTPUT_MIX) {

            // if the output returned by getOutputForEffect() is removed before we lock the

            // mutex below, the call to checkPlaybackThread_l(output) below will detect it

            // and we will exit safely

            output = AudioSystem::getOutputForEffect(&desc);

        }

    }



    {

        Mutex::Autolock _l(mLock);





        if (!EffectIsNullUuid(&pDesc->uuid)) {

            // if uuid is specified, request effect descriptor

            lStatus = EffectGetDescriptor(&pDesc->uuid, &desc);
@@ -4744,17 +4759,9 @@ sp<IEffect> AudioFlinger::createEffect(pid_t pid, 


        // If output is not specified try to find a matching audio session ID in one of the

        // output threads.

        // TODO: allow attachment of effect to inputs

        // If output is 0 here, sessionId is neither SESSION_OUTPUT_STAGE nor SESSION_OUTPUT_MIX

        // because of code checking output when entering the function.

        if (output == 0) {

            if (sessionId == AudioSystem::SESSION_OUTPUT_STAGE) {

                // output must be specified by AudioPolicyManager when using session

                // AudioSystem::SESSION_OUTPUT_STAGE

                lStatus = BAD_VALUE;

                goto Exit;

            } else if (sessionId == AudioSystem::SESSION_OUTPUT_MIX) {

                output = AudioSystem::getOutputForEffect(&desc);

                LOGV("createEffect() got output %d for effect %s", output, desc.name);

            } else {

             // look for the thread where the specified audio session is present

            for (size_t i = 0; i < mPlaybackThreads.size(); i++) {

                if (mPlaybackThreads.valueAt(i)->hasAudioSession(sessionId) != 0) {
@@ -4769,7 +4776,7 @@ sp<IEffect> AudioFlinger::createEffect(pid_t pid, 
                output = mPlaybackThreads.keyAt(0);

            }

        }

        }

        LOGV("createEffect() got output %d for effect %s", output, desc.name);

        PlaybackThread *thread = checkPlaybackThread_l(output);

        if (thread == NULL) {

            LOGE("createEffect() unknown output thread");
@@ -4777,6 +4784,8 @@ sp<IEffect> AudioFlinger::createEffect(pid_t pid, 
            goto Exit;

        }



        // TODO: allow attachment of effect to inputs



        wclient = mClients.valueFor(pid);



        if (wclient != NULL) {