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From: Duncan Sands <duncan.sands@math.u-psud.fr>
To: David Brownell <david-b@pacbell.net>
Subject: Re: [linux-usb-devel] Re: 2.5.8-pre3: kernel BUG at usb.c:849! (preempt_count 1)
Date: Thu, 11 Apr 2002 00:20:10 +0200
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Cc: Kernel List <linux-kernel@vger.kernel.org>, rml@tech9.net,
        linux-usb-devel@lists.sourceforge.net,
        Johannes Erdfelt <johannes@erdfelt.com>
In-Reply-To: <E16vHsQ-0000Jy-00@baldrick> <E16vLJx-00028n-00@baldrick> <071e01c1e0b4$64f382e0$6800000a@brownell.org>
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On Wednesday 10 April 2002 7:23 pm, David Brownell wrote:
> > > And what usb device driver(s) were supposed to have stopped
> > > using "device 3"?  I've only noticed such device refcounting bugs
> > > being caused by the USB device drivers with bad disconnect()
> > > routines, not usbcore or any of the host controller drivers, but of
> > > course that can change.
> >
> > Ha!
> >
> > $ cat /proc/bus/usb/drivers
> >          usbfs
> >          hub
> >
> > There are no other drivers!  I have a USB webcam and a modem
> > ... has a user space driver that works via usbfs.
>
> ... OK, this is sounding familiar.  "usbfs" has some recently noted
> bugs in its disconnect() routine.  That SpeedTouch driver seems to
> be triggering them with regularity, though more often with usb-ohci.
>
> The ksymoops info you sent is compatible with the bug being in
> the usbfs code:  exactly what I'd expect such a BUG() to show.
>
> I hate to send around untested patches, but I think the one I've
> attached is at least in the right direction.  (Attachment, to avoid
> mangling by mailers...)  It's an update of what I sent around late
> last month to address someone's SpeedTouch oopsing with
> usb-ohci (!) on 2.4.19-pre2, redone against 2.5.8-pre3, which
> compiles.  I hope it doesn't create new oopses.
>
> If it works for you, let us know ...
>
> - Dave

It seems to work - thanks!  I will test more, but so far so good.
System shutdown still completes with "preempt_count = 1"
though.

All the best,

Duncan.

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