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    SubjectRe: [linux-pm] wacom + runtime PM = AA deadlock
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    On Monday, September 13, 2010 01:02:16 pm Alan Stern wrote:
    > 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?

    No need - input core will not call dev->open() twice.

    --
    Dmitry


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