Date 4.4.2013 11:27, mateen wrote: > Hi, > > I seeing sometimes deadlock issue with dmix when I press CTRL+C. > > Aplay's signal handler calls snd_pcm_close() if an interrupt occurs. > snd_pcm_close() will internally call pcm->ops->close() which will fall to > snd_pcm_dmix_close() in case you are using dmix. > > snd_pcm_dmix_close() will try to acquire the semaphore with > snd_pcm_direct_semaphore_down(dmix, DIRECT_IPC_SEM_CLIENT). > The same semaphore is acquired in snd_pcm_dmix_sync_area() with > dmix_down_sem() in case of non-concurrent access. > > If semaphore is acquired in snd_pcm_dmix_sync_area() which is in thread > context and interrupt comes, which invokes the signal handler which is in > ISR context, which calls snd_pcm_close() which in turn calls > snd_pcm_dmix_close() then we see a deadlock since semaphore is not released > from thread context and ISR is waiting indefinitely on the same semaphore. > > Please suggest a suitable solution for this. It seems that also other configurations (alsa-lib plugins) have trouble with the closing from the signal handler - I hit mutex issues with the PulseAudio plugin, too. The question is, how we can do a clean path in this case. Looking to the current alsa-lib code, I would suggest to add the snd_pcm_abort() function (may be called from the interrupt handler) to notify the library to not ignore -EINTR return codes from poll() and other i/o ops and pass it to the caller (application) to finish the normal close sequence. Opinions? Jaroslav -- Jaroslav Kysela <perex@xxxxxxxx> Linux Kernel Sound Maintainer ALSA Project; Red Hat, Inc. _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
