linux-kernel - Re: [linux-usb-devel] USB deadlock after resume

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Date:	Wed, 21 Nov 2007 11:31:13 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Markus Rechberger <mrechberger@...il.com>
cc:	Oliver Neukum <oliver@...kum.org>,
	Laurent Pinchart <laurentp@...-semaphore.com>,
	Mark Lord <lkml@....ca>, <linux-kernel@...r.kernel.org>,
	<linux-usb-devel@...ts.sourceforge.net>
Subject: Re: [linux-usb-devel] USB deadlock after resume

On Wed, 21 Nov 2007, Markus Rechberger wrote:

> > > it's not just usb_set_interface that hangs actually.
> > > It seems to hang at
> > >
> > > wait_event(usb_kill_urb_queue, atomic_read(&urb->use_count) == 0);
> > >
> > > in drivers/usb/core/urb.c after resuming. I disabled access to the usb
> > > subsystem in the uvc driver, although connecting any other usb storage
> > > fails too, just at the same point.
> >
> > Which URB is usb_kill_urb() called for?
> >
> 
> it's the usb_control_message which calls usb_kill_urb if I haven't got
> it wrong. (if you're looking for some other information please let me
> know)
> Although, I got a bit further with it. The error seems to happen
> earlier already.
> If I load the driver, and do not access the device after suspending
> all usb_control commands fail with -71 eproto.

That's very strange.  Getting -71 errors is understandable; it 
indicates that the device can't handle being suspended.  But the 
wait_event() line still shouldn't hang.  If it does, it indicates that 
there's something wrong with the USB host controller, not just the 
device.

Can you try testing this on a different sort of computer?

Alan Stern

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