1057954 - [B2G debug] Intermittent test_standalone.html | ASSERTION: Decoder fired ended, but not in ended state: '!mDecoder || mDecoder->IsEnded()', file ../../../../../gecko/content/html/content/src/HTMLMediaElement.cpp, line 3043

Status: RESOLVED FIXED

(Core :: Audio/Video, defect)

Description

[JW Wang [:jwwang] [:jw_wang]]

https://tbpl.mozilla.org/php/getParsedLog.php?id=46476997&tree=Try&full=1#error0

Found this issue while running media tests on B2G emulator debug build.

08:15:58     INFO -  2261 INFO [Child 737] ###!!! ASSERTION: Decoder fired ended, but not in ended state: '!mDecoder || mDecoder->IsEnded()', file ../../../../../gecko/content/html/content/src/HTMLMediaElement.cpp, line 3043

Comment 1

[JW Wang [:jwwang] [:jw_wang]]

Here is the story that causes the assertion:

1. MediaDecoderStateMachine reaches playback completed state and wants to dispatch MediaDecoder::PlaybackEnded(). [1]
2. Since it is a sync dispatch, MediaDecoderStateMachine has to release the monitor before dispatching.
3. Meanwhiel, the main thread kicks in and MediaDecoder::SetDormantIfNecessary() is called.
4. SetDormantIfNecessary() enters the monitor and do anything necessary for dormant.
5. Now it is MediaDecoder::PlaybackEnded()'s turn which tries change state to PLAY_STATE_ENDED but it fails silently for ChangeState() will just return in dormant state. [2]
6. Following step 5, HTMLMediaElement::PlaybackEnded() is called in MediaDecoder::PlaybackEnded().
7. It hits the assertion for the play state of MediaDecoder didn't change to PLAY_STATE_ENDED.


[1] http://hg.mozilla.org/mozilla-central/file/1db35d2c9a2f/content/media/MediaDecoderStateMachine.cpp#l2471
[2] http://hg.mozilla.org/mozilla-central/file/1db35d2c9a2f/content/media/MediaDecoder.cpp#l1166

Comment 2

[JW Wang [:jwwang] [:jw_wang]]

Attachment: 1057954_fix_MediaDecoder_playbackEnded_after_dormant-v1.patch

See comment 1 for the root cause.

Fix: MediaDecoder::PlaybackEnded should just return in dormant state. MediaDecoder and MediaDecoderStateMachine will change state properly when leaving dormant state.

Comment 3

[JW Wang [:jwwang] [:jw_wang]]

Attachment: 1057954_fix_MediaDecoder_playbackEnded_after_dormant-v2.patch

Fix parenthesis warnings.

Comment 4

[JW Wang [:jwwang] [:jw_wang]]

Try: https://tbpl.mozilla.org/?tree=Try&rev=318da9fcc2d7
Most green.

Comment 5

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/8cc63a38bfc7

Comment 6

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/8cc63a38bfc7