[alsa-devel] [alsa-lib] Query regarding snd_config_update_free_global() and threads etc.

Colin Guthrie gmane at colin.guthr.ie
Mon Aug 23 17:49:54 CEST 2010

'Twas brillig, and Jaroslav Kysela at 23/08/10 16:13 did gyre and gimble:
> On Mon, 23 Aug 2010, Colin Guthrie wrote:
>> Hi there,
>> I've got a (hopefully quick) query about snd_config_update_free_global()
>> and it's general thread safetyness.
>> I'm currently going insane on this bug:
>> https://bugs.kde.org/show_bug.cgi?id=232068
>> which revolves around a bug manifested in snd_pcm_close() (or rather
>> snd_pcm_ioplug_close()) when dealing with the ALSA->PulseAudio plugin.
>>> From what I can gather, this problem is related to a KDE module that is
>> loaded into the library in question which does some alsa probing and
>> ultimately calls snd_config_update_free_global() several times. The
>> library itself then goes on to use GStreamer to do actual audio output.
>> The crash then manifests itself prior to any sound actually being output.
>> I can reliably reproduce the machine on two machines (I don't have many
>> at my disposal), but cannot reproduce on a third. The two I can
>> reproduce it on are two and four core intel duo's. The one I cannot
>> reproduce on is an older, single core machine. I am leaning towards some
>> kind of thread safety issue.
>> In searching for similar problems, I found several references to similar
>> crashes attributed to snd_dlobj_cache_cleanup() perhaps not being thread
>> safe.
> I tried to work on snd_dlobj_cache issues. Please, could you test this 
> patch?
> http://git.alsa-project.org/?p=alsa-lib.git;a=commitdiff;h=91c9c8f1b85e69b4bdc94a777d2767c4906c3f47

Sure, will try and do so this evening and report back. Thanks!



Colin Guthrie

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Open Source:
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  PulseAudio Hacker [http://www.pulseaudio.org/]
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