Nouveau - Jul 2017 - [regression drm/noveau] suspend to ram -> BOOM: exception RIP: drm_calc_vbltimestamp_from_scanoutpos+335

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 at gmail.com>

On Fri, Jul 14, 2017 at 5:05 PM, Tobias Klausmann
<tobias.johannes.klausmann at mni.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",
>> +                         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 at gmail.com>
> _______________________________________________
> Nouveau mailing list
> Nouveau at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/nouveau

On Fri, 2017-07-14 at 17:10 +0200, Karol Herbst wrote:
> Yeah, we shouldn't let the machine die. Are there more WARN_ON_ONCE
> usage we could convert to WARN_ONCE?
Shooting the messenger is generally considered uncool :)

	-Mike

On Fri, Jul 14, 2017 at 11:15 AM, Mike Galbraith <efault at gmx.de>
wrote:
> On Fri, 2017-07-14 at 17:10 +0200, Karol Herbst wrote:
>> Yeah, we shouldn't let the machine die. Are there more WARN_ON_ONCE
>> usage we could convert to WARN_ONCE?
>
> Shooting the messenger is generally considered uncool :)
That's never stopped it from being a popular practice...

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 at mni.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 at gmail.com>
>
> On Fri, Jul 14, 2017 at 5:05 PM, Tobias Klausmann
> <tobias.johannes.klausmann at mni.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 at gmail.com>
>> _______________________________________________
>> Nouveau mailing list
>> Nouveau at lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/nouveau

On Fri, Jul 14, 2017 at 11:19 AM, Tobias Klausmann
<tobias.johannes.klausmann at mni.thm.de> wrote:
> 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 at mni.thm.de>
I don't think it was meant as a serious patch. WARN_ON_ONCE should
work. The fix isn't to remove all instances of WARN_ON_ONCE. The fix
is to fix WARN_ON_ONCE.