[Pkg-alsa-devel] Bug#560212: Bug#560212: alsa-source: Driver snd-hrtimer - causing system freeze with Rosegarden

[Elimar Riesebieter]

severity 560212 normal
thanks

* wzabolot at elektron.elka.pw.edu.pl [091209 20:27 +0100]
> Package: alsa-source
> Version: 1.0.21+dfsg-2
> Severity: important
> 
> *** Please type your report below this line ***
> 
> When I try to use the "HR timer" as a MIDI sequencer timer in the
> Rosegarden (http://www.rosegardenmusic.com) application, the system
> freezes. Another people also reported similar problems with other
> sequencer - OpenOctave (
> https://linuxmusicians.com/viewtopic.php?f=27&p=8917 )
> 
> I have tested the problem on two SMP machines with diffrent kernels
> (2.6.30, 2.6.31.6, 2.6.32).
> The problem seems to be associated with the "snd-hrtimer" module.
> I've tried to run the application vie remote X session, while having the
> text console active.
> Before the machine froze, the following messages have been displayed in
> the console:
> 
> System 1 (Intel(R) Pentium(R) 4 CPU 2.80GHz HT)
> 
> hrtimer: interrupt too slow, forcing clock min delta to 3568 ns
> 
> System 2 (Intel(R) Core(TM)2 CPU         T5500  @ 1.66GHz)
> hrtimer: interrupt too slow, forcing clock min delta to 11103 ns
> CE: hpet increasing min_delta_ns to 15000 nsec
> CE: hpet increasing min_delta_ns to 22500 nsec
> CE: hpet increasing min_delta_ns to 33750 nsec
> 
> Analyzing the problem, I had an idea, that maybe the snd-hrtimer should
> be rewritten to call
> the callback via tasklet (I attach my patch only as an ilustration, my
> code doesn't work either),
>  however then I got the message "BUG: scheduling while atomic" or
> something like this
>  from the snd_hrtimer_stop function called from _snd_timer_stop.
> Therefore I've tried to investigate the snd_hrtimer_stop more thoroughly.
> 
> Looking further into the code, I have found, that snd_hrtimer_stop may
> be called
> from the callback routine (e.g.:
> http://lxr.linux.no/linux+v2.6.32/sound/core/timer.c#L709 or
> http://lxr.linux.no/linux+v2.6.32/sound/core/timer.c#L719 )
> 
> It seems to me, that calling hrtimer_cancel (in the original code),
> which waits for the handler to finish,
> from that handler  may lock the machine...
> (snd_hrtimer_callback calls the snd_timer_interrupt:
> http://lxr.linux.no/linux+v2.6.32/sound/core/hrtimer.c#L47
> which in turn calls snd_hrtimer_stop (as above) which calls hrtimer_cancel).
> 
> 
> Unfortunately currently I have no idea how to fix this problem. Maybe
> snd_hrtimer_stop shouldn't try to cancel the timer,
> instead setting a flag causing callback to return immediately without
> rearming of the timer?

Did you tried in conjinction with jackd? Else wait for the new
1.0.22.1 drivers. will be uploaded soon.

Elimar


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