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Commit a38e1f4e authored by Dongwon Kang's avatar Dongwon Kang
Browse files

Make MediaSessionService not blocked by AudioService. 

Backgroud: As noted in b/20823981, MediaSessionService calls some
audio service methods while holding a lock and the audio service
methods also talk to other system services. And, deadlock happens when
the other system service fires another request to MediaSessionService
while holding its lock.

Example1) --- resolved by the change in MediaSessionRecord.java
T1: MediaSessionService.dispatchAdjustVolumeLocked()
     -> MediaSessionRecord.adjustVolume()
       -> +++AudioServiceInternal.adjustSuggestedStreamVolumeForUid()+++
         -> AudioService.adjustSuggestedStreamVolume()
           -> telecom.TelecomManager.isInCall() --- blocked by lock in TelecomManager.
T2: telecom.ConnectionServiceWrapper.handleCreateConnectionComplete()
     -> MediaSession.setActive()
       -> MediaSessionRecord$SessionStub.setActive()
         -> MediaSessionService.updateSession() --- blocked by lock in MediaSessionService.

Example2) --- resolved by the change in IAudioService.aidl
T1: MediaSessionService.dispatchAdjustVolumeLocked()
     -> IAudioService.adjustSuggestedStreamVolume()
       -> AudioService.adjustSuggestedStreamVolume()
         -> telecom.TelecomManager.isInCall() --- blocked by lock in TelecomManager.
T2: telecom.ConnectionServiceWrapper.handleCreateConnectionComplete()
     -> MediaSession.setActive()
       -> MediaSessionRecord$SessionStub.setActive()
         -> MediaSessionService.updateSession() --- blocked by lock in MediaSessionService.

Here, this change prevents the deadlock by making related audio IPC oneway
and calling the internal audio method without holding the lock.

Bug: 20823981
Change-Id: I4c4b2fc796f23d83be67f7edaacd7496c145d985
parent 2d4dc8db

media/java/android/media/IAudioService.aidl

+1 −1
Original line number Original line Diff line number Diff line
@@ -40,7 +40,7 @@ import android.view.KeyEvent; 
 */

 */

interface IAudioService {

interface IAudioService {





    void adjustSuggestedStreamVolume(int direction, int suggestedStreamType, int flags,

    oneway void adjustSuggestedStreamVolume(int direction, int suggestedStreamType, int flags,

            String callingPackage, String caller);

            String callingPackage, String caller);





    void adjustStreamVolume(int streamType, int direction, int flags, String callingPackage);

    void adjustStreamVolume(int streamType, int direction, int flags, String callingPackage);

services/core/java/com/android/server/media/MediaSessionRecord.java

+27 −7
Original line number Original line Diff line number Diff line
@@ -242,19 +242,17 @@ public class MediaSessionRecord implements IBinder.DeathRecipient { 
        }

        }

        if (mVolumeType == PlaybackInfo.PLAYBACK_TYPE_LOCAL) {

        if (mVolumeType == PlaybackInfo.PLAYBACK_TYPE_LOCAL) {

            int stream = AudioAttributes.toLegacyStreamType(mAudioAttrs);

            int stream = AudioAttributes.toLegacyStreamType(mAudioAttrs);

            // Adjust the volume with a handler not to be blocked by other system service.

            if (useSuggested) {

            if (useSuggested) {

                if (AudioSystem.isStreamActive(stream, 0)) {

                if (AudioSystem.isStreamActive(stream, 0)) {

                    mAudioManagerInternal.adjustSuggestedStreamVolumeForUid(stream, direction,

                    postAdjustSuggestedStreamVolume(stream, direction, flags, packageName, uid);

                            flags, packageName, uid);

                } else {

                } else {

                    flags |= previousFlagPlaySound;

                    flags |= previousFlagPlaySound;

                    mAudioManagerInternal.adjustSuggestedStreamVolumeForUid(

                    postAdjustSuggestedStreamVolume(AudioManager.USE_DEFAULT_STREAM_TYPE, direction,

                            AudioManager.USE_DEFAULT_STREAM_TYPE, direction, flags, packageName,

                            flags, packageName, uid);

                            uid);

                }

                }

            } else {

            } else {

                mAudioManagerInternal.adjustStreamVolumeForUid(stream, direction, flags,

                postAdjustStreamVolume(stream, direction, flags, packageName, uid);

                        packageName, uid);

            }

            }

        } else {

        } else {

            if (mVolumeControlType == VolumeProvider.VOLUME_CONTROL_FIXED) {

            if (mVolumeControlType == VolumeProvider.VOLUME_CONTROL_FIXED) {
@@ -461,6 +459,28 @@ public class MediaSessionRecord implements IBinder.DeathRecipient { 
        return mPackageName + "/" + mTag;

        return mPackageName + "/" + mTag;

    }

    }





    private void postAdjustSuggestedStreamVolume(final int streamType, final int direction,

            final int flags, final String callingPackage, final int uid) {

        mHandler.post(new Runnable() {

            @Override

            public void run() {

                mAudioManagerInternal.adjustSuggestedStreamVolumeForUid(streamType, direction,

                        flags, callingPackage, uid);

            }

        });

    }



    private void postAdjustStreamVolume(final int streamType, final int direction, final int flags,

            final String callingPackage, final int uid) {

        mHandler.post(new Runnable() {

            @Override

            public void run() {

                mAudioManagerInternal.adjustStreamVolumeForUid(streamType, direction, flags,

                        callingPackage, uid);

            }

        });

    }



    private String getShortMetadataString() {

    private String getShortMetadataString() {

        int fields = mMetadata == null ? 0 : mMetadata.size();

        int fields = mMetadata == null ? 0 : mMetadata.size();

        MediaDescription description = mMetadata == null ? null : mMetadata

        MediaDescription description = mMetadata == null ? null : mMetadata