linux-kernel - Re: [Nouveau] [regression drm/noveau] suspend to ram -> BOOM: exception RIP: drm_calc_vbltimestamp_from_scanoutpos+335

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Date:   Fri, 14 Jul 2017 17:19:02 +0200
From:   Tobias Klausmann <tobias.johannes.klausmann@....thm.de>
To:     Karol Herbst <karolherbst@...il.com>
Cc:     Mike Galbraith <efault@....de>, Ilia Mirkin <imirkin@...m.mit.edu>,
        Peter Zijlstra <peterz@...radead.org>,
        David Airlie <airlied@...ux.ie>,
        "nouveau@...ts.freedesktop.org" <nouveau@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        Ben Skeggs <bskeggs@...hat.com>
Subject: Re: [Nouveau] [regression drm/noveau] suspend to ram -> BOOM:
 exception RIP: drm_calc_vbltimestamp_from_scanoutpos+335

The conversion is a nice catch, but i'd like to have a bit more context, 
see below!

With a better description:

Tobias Klausmann <tobias.johannes.klausmann@....thm.de>

On 7/14/17 5:10 PM, Karol Herbst wrote:
> Yeah, we shouldn't let the machine die. Are there more WARN_ON_ONCE
> usage we could convert to WARN_ONCE?
>
> Reviewed-By: Karol Herbst <karolherbst@...il.com>
>
> On Fri, Jul 14, 2017 at 5:05 PM, Tobias Klausmann
> <tobias.johannes.klausmann@....thm.de> wrote:
>> On 7/14/17 3:41 PM, Mike Galbraith wrote:
>>> On Fri, 2017-07-14 at 15:36 +0200, Mike Galbraith wrote:
>>>>    All DRM did was to slip a
>>>> WARN_ON_ONCE() that nouveau triggers into a kernel module where such
>>>> things no longer warn, they blow the box out of the water.
>>> BTW, turn that irksome WARN_ON_ONCE() in drivers/gpu/drm/drm_vblank.c
>>> into a WARN_ONCE(), and all is peachy, you get the warning, box lives.
>>>
>>> ---
>>>    drivers/gpu/drm/drm_vblank.c |    3 ++-
>>>    1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> --- a/drivers/gpu/drm/drm_vblank.c
>>> +++ b/drivers/gpu/drm/drm_vblank.c
>>> @@ -605,7 +605,8 @@ bool drm_calc_vbltimestamp_from_scanoutp
>>>           */
>>>          if (mode->crtc_clock == 0) {
>>>                  DRM_DEBUG("crtc %u: Noop due to uninitialized mode.\n",
>>> pipe);
>>> -               WARN_ON_ONCE(drm_drv_uses_atomic_modeset(dev));
>>> +               WARN_ONCE(drm_drv_uses_atomic_modeset(dev), "%s: report
>>> me.\n",

"report me" seems a bit odd, maybe just uninitialized mode?

>>> +                         dev->driver->name);
>>>                  return false;
>>>          }
>>
>>
>> Hey,
>>
>> confirmed this helps saving the box, but we still have to find the root
>> cause! Backtrace with the above fix applied (and the one which came in with
>> the latest drm-fixes merge)!
>>
>>
>> [1] https://hastebin.com/uyoqifijed.http
>>
>> Thanks,
>>
>> Tobias
>> Reviewed-By: Karol Herbst <karolherbst@...il.com>
>> _______________________________________________
>> Nouveau mailing list
>> Nouveau@...ts.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/nouveau

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