Subject: Re: bug#63197: video acceleration/libva segfaults caused by stale mesa shader cache

From: Giovanni Biscuolo <[email-masked]>
Date: Thu, 15 Jun 2023 15:49:50 +0200

Hi Maxim,

I learned about this issue today

Maxim Cournoyer <[email-masked]> writes:

[...]

>> After tracing the process, I noticed that the last thing it did was
>> loading its mesa shader cache, stored under:
>>
>> ~/.cache/mesa_shader_cache
>>
>> Deleting that directory resolved the issue.
>>
>> It seems that'd be a bug in Mesa (for failing to determine that it
>> should have invalidated its cache going from version 21 to 22 post
>> core-updates merge).

AFAIU this issue is still present using mesa 23 since Guillaume Le
Vaillant had to use this workaround yesterday [1] and reported his
backtrace upstream [2]

If I'm not wrong (i.e. vlc et al are now using mesa 23) this should also
be reported upstream (I can do it if needed).

AFAIU the only thing we can do to fix this bug is to disable the shader
cache (MESA_SHADER_CACHE_DISABLE=true) until a proper fix is found
upstream.

...or apply a patch to rename "~/.cache/mesa_shader_cache" to
"~/.cache/mesa<version>_shader_cache"

Alternatively, we should find a way to make Guix users aware of this
kind of problems and possible workarounds they can apply (it's not
related to this specific bug)

WDYT?

Thanks! Gio'

[1] id:871qify1i8.fsf@kitej

[2] https://gitlab.freedesktop.org/mesa/mesa/-/issues/8937#note_1960628

-- 
Giovanni Biscuolo

Xelera IT Infrastructures