From mboxrd@z Thu Jan  1 00:00:00 1970
From: Daniel Vetter <daniel@ffwll.ch>
Subject: Re: [PATCH v2 1/2] drm/i915: fix possible refcount leak
 when resetting forcewake
Date: Fri, 6 Jun 2014 22:15:32 +0200
Message-ID: <20140606201532.GV7416@phenom.ffwll.local>
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On Fri, Jun 06, 2014 at 09:38:26PM +0300, Imre Deak wrote:
> On Fri, 2014-06-06 at 19:46 +0200, Daniel Vetter wrote:
> > On Fri, Jun 06, 2014 at 12:08:43PM +0100, Chris Wilson wrote:
> > > On Fri, Jun 06, 2014 at 02:04:37PM +0300, Imre Deak wrote:
> > > > If the timer putting the last forcewake refcount was pending and we
> > > > canceled it, we'll leak the corresponding forcewake and RPM references.
> > > > 
> > > > v2:
> > > > - do the ptr casting at the caller instead of adding a separate helper
> > > >   for this (Chris)
> > > > 
> > > > Signed-off-by: Imre Deak <imre.deak@intel.com>
> > > Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
> > 
> > Both patches merged to dinq (Chris clarified on irc that his r-b is for
> > both).
> >
> > Since this only blows up in a super-contrived testcase I don't
> > think this is material for -fixes.
> 
> Note that the issue fixed by 1/2 could also happen normally, though the
> window for race is small. One scenario would be runtime resume
> ->deferred rps_enable followed directly by system suspend or gpu reset.

The default runtime pm autosuspend delay is longer than the delayed rps
enable, so for all practical purposes I think this is impossible.

But once we set the autoresume delay to something more sane (100ms maybe,
patches anyone?) we definitely need this patch here.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch