Re: USB Audio problems

[Takashi Iwai <tiwai@suse.de>]

At Thu, 20 Nov 2003 23:33:52 +0900,
Patrick Shirkey wrote:
> 
> Takashi Iwai wrote:
> > 
> > the current code is surely buggy, because it issues sync unlink
> > inside the spinlocked context.  it's problematic on 2.6 kernel or SMP
> > system, and may result in kernel oops.  i added async_unlink module
> > option to change the behavior in the new version.
> > 
> > but it's still disabled as default, because unlinking multiple urbs
> > asynchronouly on 2.4 kernel causes kernel panic.  sigh.
> > unfortunately, there is no perfect solution to satisfy all versions
> > yet.  perhaps we need to redesign the linked-pcm streams to make it
> > possible to call prepare callback without spinlocks.
> > 
> >
> 
> Ahhh, Finally an explanaiton for why my root /var/ partition is always 
> being filled up with usb errors.
> 
> Would this also have a detrimental effect on latency? If so then I can 
> let other usb-audio user know why.

no, it has nothing to do with the latency but oopsen / lock-up.
the problem exists only at stopping the streams.  if the everything is
ok, it's not a big issue.  but, when the device runs with small
latency, which may result in xrun often, has the higher probability to
hit this bug, because ALSA tries to stop the stream if xrun happens.


Takashi


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