linux-kernel - Re: [linux-pm] wacom + runtime PM = AA deadlock

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Message-ID: <Pine.LNX.4.44L0.1009140954180.1648-100000@iolanthe.rowland.org>
Date:	Tue, 14 Sep 2010 10:01:14 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Oliver Neukum <oneukum@...e.de>
cc:	Jiri Slaby <jslaby@...e.cz>, Dmitry Torokhov <dtor@...l.ru>,
	<pingc@...om.com>, linux-pm <linux-pm@...ts.linux-foundation.org>,
	Linux kernel mailing list <linux-kernel@...r.kernel.org>,
	<linux-input@...r.kernel.org>
Subject: Re: [linux-pm] wacom + runtime PM = AA deadlock

On Tue, 14 Sep 2010, Oliver Neukum wrote:

> Am Montag, 13. September 2010, 22:02:16 schrieb Alan Stern:
> > > > 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.
> 
> Should I have used usb_autopm_get_interface_no_resume()?

That actually would work.  It's a good idea.  The only drawback (not a
big one) is that if the device _was_ suspended with remote wakeup
enabled, doing this wouldn't turn off remote wakeup.  I think that
doesn't matter.

Alan Stern

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