Re: [BUG] usb_set_device_state

[Rafael J. Wysocki]

On Sunday, February 06, 2011, Minchan Kim wrote:
> On Sun, Feb 6, 2011 at 9:03 PM, Rafael J. Wysocki <rjw@xxxxxxx> wrote:
> > On Sunday, February 06, 2011, Rafael J. Wysocki wrote:
> >> On Sunday, February 06, 2011, Alan Stern wrote:
> >> > 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.
> >>
> >> No, I'm not.  At least not with 2.6.37.
> >>
> >> Also, I think the problem would have been reported before if it had been that
> >> easy to reproduce with the mainline kernel.
> >
> > Or do I need to enable a specific CONFIG_ option to reproduce it?
> >
> > Rafael
> >
> 
> When I am googling, I found https://lkml.org/lkml/2011/1/14/440.
> Maybe the bug is caused by that.
> It is in linux-next and mmotm, not linus tree.

Yes, it is, thanks!

I'll revert the patch for now and see how it can be fixed.

Rafael
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