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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 13 Sep 2010 16:02:16 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Oliver Neukum <oliver@...kum.org>
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 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

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/