[Webkit-unassigned] [Bug 258876] [GStreamer][MSE] Crashes on https://www.apple.com/macbook-air-13-and-15-m2/

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=258876

--- Comment #9 from Alicia Boya García <aboya at igalia.com> ---
(In reply to kdwkleung from comment #0)
> **
> ERROR:../gst/codecalpha/gstalphacombine.c:160:gst_alpha_combine_unlock_stop:
> assertion failed: (self->flushing)
> Bail out!
> ERROR:../gst/codecalpha/gstalphacombine.c:160:gst_alpha_combine_unlock_stop:
> assertion failed: (self->flushing)
> 
> (epiphany:2): epiphany-WARNING **: 18:35:48.591: Web process crashed
> 
> 
> 
> 
> This is tested on Epiphany Technology Preview/ WebKitGTK 2.41.6, it worked
> fine in 2.41.5

I heavily suspect this is https://bugs.webkit.org/show_bug.cgi?id=244776 in action. In fact, it's the same outcome: an element downstream of decodebin3 (in this case alphacombine) is receiving a FLUSH_STOP without receiving a FLUSH_START.

I first was made aware of this happening from seeing a similar assertion failing in WebKitVideoSink after it was corrected to use AbortableTaskQueue, and therefore able to handle flushes. I think most people didn't care much about it because it WebKit debug assertions get stripped for release builds.

I've long deduced the race condition is in core GStreamer elements and cannot be easily fixed in WebKit alone. Since a few weeks ago I've finally been able to dedicate more time to investigating this race condition.

I've made good progress on that: I found it's not just one race condition, but several similar races in several elements: decodebin3, playsink and playsinkconvertbin. I've also been able to fix them locally, and I'm currently working towards verifying and upstreaming them.

Unfortunately that also means it's not an easy task and the fixes need not only to be approved in upstream GStreamer but will require new GStreamer versions or GStreamer patches in flatpak.

-- 
You are receiving this mail because:
You are the assignee for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.webkit.org/pipermail/webkit-unassigned/attachments/20230707/c7bc5751/attachment.htm>