[LAD] snd-usb-audio dying on jackd xruns

[Gabriel Beddingfield]

Hi Rods,

On Wed, Feb 2, 2011 at 1:08 PM, Rods Bobavich <rodnisms at gmail.com> wrote:
> I was looking at the wrong urb.c file. The correct one is
> linux-kernel/sound/usb/urb.c
> Actually the KERN_ERR is on 138 for my version triggers as line 146...
> On line 460 is the second KERN_ERR.
> This is all in a function called retire_capture_urb()

Which kernel?

> It appears that there is a commented continue that would drastically change
> the for-loop this one is in. I wonder... Could this be the offending line?
> If I'm reading the code correctly it appears to be some sort of locking
> mechanism check while retiring the urb from use to make sure it is retired
> when it is no longer active. Without the continue the urb will still be
> retired. Perhaps this is causing something unstable?
> Clemens might know more about this. I'm not that familiar with kernel code.

Shooting from the hip (and also digging in 2.6.26.5 sources)... looks
like there was a timeout when calling usb_set_interface()
(drivers/usb/core/message.c).  The urb transfers look like they
stalled rather than failed to allocate bandwidth.  That makes me think
there's a bad cable, bad USB controller, bad USB controller /driver/,
bad format request, bad device, or something like that.

-gabriel