Bug#660803: oss-compat 3 problems with udev and breaks audio

[Sven Joachim]

Guess I might chime in here, since I'm having the same problem as
Michael on one of my machines - but only with recent self-built kernels,
not with the official Debian 3.9 kernel or any of the long-term kernels
(3.4 and earlier).  I had already done some work on it, but found a
workaround and didn't bother to do further research.

On 2013-06-27 20:21 +0200, Stephen Kitt wrote:

> On Thu, 27 Jun 2013 16:20:26 +0200, Michael Hatzold <m.hatzold at web.de> wrote:
>> - manually deleting "/etc/modprobe.d/oss-compat.conf" lets alsa configure
>> the soundcard at next boot (but then applications depending on oss-compat
>> won't work).
>> - apt-get install oss-compat/testing" *won't* work, as it does not replace
>> /etc/modprobe.d/oss-compat.conf (v3) with /etc/modprobe.d/oss-compat.conf
>> (v2)
>> - apt-get install oss-compat/testing" *will* work if you remove
>> /etc/modprobe.d/oss-compat.conf beforehand.
>> 
>> To me it seems that the new format of /etc/modprobe.d/oss-compat.conf is the
>> main problem.
>
> That is indeed the logical conclusion if the v2 file works whereas the v3
> file doesn't. There must be something related to your particular
> configuration though since the v3 file does work on some computers ;-).
>
> Could you possibly try the following?
> * re-install oss-compat 3
> * reboot (with the timeout)
> * run
> 	sudo udevadm --debug trigger --verbose
>   to re-attempt to load the sound modules and trace what is attempted

Actually the modules might load fine in that case, only the _first_
modprobe was broken for me.  What I did to debug the problem was to
blacklist snd-hda-intel (thereby bypassing the udev timeout) and then
manually run modprobe under strace to see where it hangs.  Attached is
the output of "strace -f modprobe snd-seq-oss" with a self-compiled
3.10.0-rc6 kernel, where init_module() was hung on snd-seq-oss.ko.

Manually killing modprobe at this stage actually succeeded loading the
modules, and what I finally did was to comment out the line with

softdep snd-seq post: snd-seq-midi snd-seq-oss

in oss-compat.conf.

Now I could of course do a bisection on the kernel, but this is going to
take a considerable amount of time, and I'm not to keen to do that
unless I absolutely have to.

Cheers,
       Sven

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