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Subject: Re: System freeze on shutdown - bisected to commit 29d08b3efddc
From: Ben Skeggs <skeggsb@gmail.com>
Reply-To: skeggsb@gmail.com
To: Marc Dionne <marc.c.dionne@gmail.com>
Cc: Dave Airlie <airlied@redhat.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Date: Thu, 07 Oct 2010 13:38:26 +1000
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v	gOn Wed, 2010-10-06 at 23:29 -0400, Marc Dionne wrote:
> On Tue, Oct 5, 2010 at 8:21 PM, Dave Airlie <airlied@redhat.com> wrote:
> > On Tue, 2010-10-05 at 18:24 -0400, Marc Dionne wrote:
> >> Hi,
> >>
> >> My system has been crashing these past few days when issuing "reboot"
> >> or hitting the Shut Down button in gnome.  I get a series of stack
> >> traces scrolling on the console before things freeze up completely.
> >> The traces that I do see at the end point to kmem_cache_alloc called
> >> from get_empty_filp, but there are typically various other traces
> >> above it.
> >
> > cc'ing Ben.
> >
> > Dave.
> 
> Some more testing shows that what causes the crash is when
> drm_gem_object_unreference_unlocked gets called in
> nouveau_notifier_takedown_channel.  The refcount on the object is
> always 1 at that point - on entry to nouveau_notifier_takedown I see a
> handle_count of 0 and a refcount of 1 in most cases, and sometimes a
> handle_count of 1 and a refcount of 2.  Either way the call to
> drm_gem_object_unreference_unlocked will bring the refcount to 0.
> Not sure if that's normal at that point.
> 
> Commenting out that particular call to
> drm_gem_object_unreference_unlocked gets rid of the crash.
How about if you remove the drm_get_object_handle_unreference_unlocked()
call from that function instead?

Ben.
> 
> Marc