linux-kernel - Re: System freeze on shutdown - bisected to commit 29d08b3efddc

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Message-ID: <AANLkTimR4JYmA4n0kGZ+mHqEfNUrxoLMAC6hW6s4-YhF@mail.gmail.com>
Date:	Wed, 6 Oct 2010 23:29:11 -0400
From:	Marc Dionne <marc.c.dionne@...il.com>
To:	Dave Airlie <airlied@...hat.com>
Cc:	Ben Skeggs <skeggsb@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: System freeze on shutdown - bisected to commit 29d08b3efddc

On Tue, Oct 5, 2010 at 8:21 PM, Dave Airlie <airlied@...hat.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.

Marc
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