Phone hangs by repeatedly taking screenshots

when i take a screenshot of the apps scope on arale, it freezes the UI for 4-5 seconds https://bugs.launchpad.net/canonical-devices-system-image/+bug/1494480

Status changed to 'Confirmed' because the bug affects multiple users.

When you reach the state where the phone hangs, it eventually resumes after several minutes but then another screenshot will make it hang again.

This lines appear in unity8.log
virtual void AalMediaPlayerControl::stop()

Failed to stop playback: Problem stopping playback on remote object
virtual QMediaPlayer::MediaStatus AalMediaPlayerControl::mediaStatus() const

virtual QMediaPlayer::MediaStatus AalMediaPlayerControl::mediaStatus() const

virtual void AalMediaPlayerControl::play()

virtual QMediaPlayer::MediaStatus AalMediaPlayerControl::mediaStatus() const

virtual QMediaPlayer::MediaStatus AalMediaPlayerControl::mediaStatus() const

void AalMediaPlayerService::play()
Failed to check if source is video: org.freedesktop.DBus.Error.NoReply: Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.

This has been fixed by:

https://code.launchpad.net/~lukas-kde/unity8/asyncScreenshots/+merge/277894

I just reproduced this on v195 by taking 3 screenshots, the shell is frozen on the greeter indefinitely, log contains same as comment #4

Ok. Comment 4 says that media stuff is blocking on a D-Bus call. I have tried it on krillin, mako and arale and could not observe this behavior. We did have a screenshot related bug recently that would block for some 2 seconds when making a screenshot, however that one has been fixed and for me it doesn't block/hang any more at all now.

If that still happens for you, and it always prints the log from comment 4, it probably implies something (I assume media-hub) being crashed before and then playing the screenshot sound hangs, waiting on a sync dbus reply from media hub.

@Pat, Jean-Baptiste: Can you try to find out more? Does this happen all the time for you? Or only after some other steps? When in this state, can you try invoking other actions that make a sound and see if those hang? Perhaps creating a notification that plays the notification sound.

Adding back media-hub as comment 4 really points towards that.

Status changed to 'Confirmed' because the bug affects multiple users.

I did not get a media-hub crash, this was on arale.
I reproduced it this time on the 9th consecutive screen shot

Unity8 is alive and reporting this every 30 secs
Failed to get current playback position: org.freedesktop.DBus.Error.NoReply: Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.

It then acts briefly and partially on a pending gesture

unity8 log http://pastebin.ubuntu.com/14075341/
media-hub log http://paste.ubuntu.com/14075550/

From comment #10 in the media-hub log, looks like media-hub is trying to do something on an internal GStreamer pipeline thread which is very bad.

Status changed to 'Confirmed' because the bug affects multiple users.

seems fixed to me