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SubjectRe: [linux-pm] wacom + runtime PM = AA deadlock
On Mon, 13 Sep 2010, Oliver Neukum wrote:

> Am Montag, 13. September 2010, 17:17:54 schrieb Alan Stern:
> > On Mon, 13 Sep 2010, Oliver Neukum wrote:
> >
> > > PM in this driver looks broken. Please try this.
> > >
> > > In short you want to drop the PM reference and depend on remote
> > > wakeup and busy marking for this driver. Currently it gets a reference
> > > on every open() but never drops it.
> > >
> > > For locking you depend on the PM core's internal lock. You simply
> > > make sure you have a PM reference during open() and close()
> >
> > Is there any point in resuming the device during close() just in order
> > to kill the interrupt URB? It seems counterproductive -- if the device
> > had been suspended then there wouldn't be any interrupt URB to kill in
> > the first place.
>
> Suppose the device does not support remote wakeup. It would never
> be autosuspended while it is open, but simply resetting the flag
> would never reach the PM layer.

Whoops, that's right. I didn't see the assignment to
needs_remote_wakeup.

How come wacom_open doesn't check to see if wacom->open is already set?

Alan Stern



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