On Thu, 6 Feb 2014, Devin Heitmueller wrote:

> Hi there,
> 
> So I have a problem in the field on kernel 3.7 which is looking more
> and more like some sort of EHCI scheduler bug (very occasional
> usb_submit_urb failures in snd-usb-audio wedge the entire USB stack
> until reboot).  Because it's only happening in the field and I cannot
> repro locally (and it's happening on lots of machines), I was
> speculating on how hard it would be to just backport in the entire
> drivers/usb tree from the latest kernel back to 3.7.

Is it possible to get any debugging information from the machines in 
the field?

> I know this is an atypical thing to consider since most devs work on
> the trunk, but can anybody give me a feel for how much breakage is
> likely to occur If I move the tree between those two revs?  Have there
> been a ton of changes to common frameworks in the kernel that
> drivers/usb relies on?
> 
> Suggestions welcome.

That's a pretty hard question to answer.  Probably the best way to find 
out is try it and see what breaks.  It may be easier to back-port just 
the EHCI driver family and not the whole stack.

I can point out that in the last one or two kernel releases there were
significant changes to the snd-usb-audio driver that affect the way it
interacts with ehci-hcd.  Just to make your life more difficult...

Alan Stern

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