On Mon, Feb 14, 2011 at 06:39:00PM +0100, Takashi Iwai wrote: > At Mon, 14 Feb 2011 09:54:01 +0100, > Clemens Ladisch wrote: > > > > Alan Stern wrote: > > > On Fri, 11 Feb 2011, Sarah Sharp wrote: > > > > I suspect it might be the audio driver, as someone on the alsa mailing > > > > list suggested the USB sound driver can't handle when one isochronous > > > > buffer in an URB has an error, but the URB status is 0. > > > > > > I don't think that can happen. The URB status won't be 0 unless all > > > the individual buffers have 0 status. > > > > In any case, the driver would then just copy garbage samples out of the > > buffer; this wouldn't affect the driver's data structures. > > > > > > From: Pierre-Louis Bossart <bossart.nospam@xxxxxxxxx> > > > > > > > > Note that this is only a work-around, it does not address the > > > > root cause of this inconsistency between urbs and PCM states. The > > > > dmesg below shows two calls to snd_urb_complete, the substream is > > > > NULL and the state is either running or stopped. This doesn't make > > > > any sense. > > > > ... > > > > ALSA urb.c:492: frame 0 active: -84 > > > > ALSA urb.c:197: cannot submit urb (err = -19) > > > > ALSA urb.c:186: NULL substream (subs->running 1) <- How is this possible? > > > > ALSA urb.c:186: NULL substream (subs->running 0) > > > > > > It's most likely a matter of the device being disconnected but the > > > device file still being open. > > > > subs->pcm_substream == NULL happens only when the device file _has_ > > been closed. > > More exactly, it's cleared the PCM close callback, so during it's > being closed :) > Looks like a race as you mentioned below, indeed. > > > > Perhaps not everything gets cleaned up the way it should when that > > > happens. > > > > There seems to be a race between snd_usb_pcm_close() and > > snd_usb_stream_disconnect(). I think a mutex taken by both functions > > should fix this; and all functions that check 'shutdown' probably need > > serializing. > > Or, rather make sure that snd_usb_release_substreams() is finished > before PCM close; actually it should be called in hw_free callback, > but currently it's skipped by the shutdown flag check. I guess this > check isn't right. > > The serialization of shutdown check is a good point, but this won't > hit actual bugs, I suppose. Ok. I don't have the audio expertise to make a patch; can you or Clemens make one for Pierre to try out? Sarah Sharp -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
