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SubjectRe: [BUG] usb_set_device_state
On Sun, 6 Feb 2011, Rafael J. Wysocki wrote:

> On Saturday, February 05, 2011, Alan Stern wrote:
> > On Sun, 6 Feb 2011, Minchan Kim wrote:
> >
> > > I got following message during booting mmotm-02-04.
...
> > > It seems usb_set_device_state disable irq by spin_lock_irqsave.
> > > But it calls device_set_wakeup_capable which ends up calling sysfs_merge_group.
> > > It calls mutex_lock. :(
> > >
> > > Is it already known BUG?
> >
> > No, it was newly introduced by changes to the
> > device_set_wakeup_capable() routine. Rafael, this sort of problem may
> > occur in other places too, since previously there was no requirement
> > that device_set_wakeup_capable() be called in process context.
>
> I'm aware of that, but it's only happend in a handful of network drivers so far.
>
> I think this is a new case in -mm, though, isn't it?

I'm not sure. The USB core does call device_set_wakeup_capable()
while holding one or more spinlocks in usb_set_device_state(), and that
routine is called in several places. You ought to be able to duplicate
the error on your own system simply by plugging in a USB hub.

Alan Stern



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