WARNING: CPU: 0 PID: 3634 at drivers/gpu/drm/drm_irq.c:1141 drm_wait_one_vblank

[Daniel Vetter]

On Wed, Jul 08, 2015 at 08:40:17AM +0200, Michal Hocko wrote:
> I have just tried to boot 4.2-rc1 and cannot seem to reproduce the issue
> anymore.
> 
> On Tue 07-07-15 10:43:58, Daniel Vetter wrote:
> [...]
> > Can you please
> > boot with drm.debug=0xf (lots more nois in dmesg with this) and reproduce?
> > I only need the last few pages before the WARNING backtrace, just to
> > understand a bit better what's going on there.
> 
> And 0xf debug level seem to paper over the problem because I do not see
> the warning even with 4.1 where I am able to reproduce this reliably.
> This suggests this is a timing sensitive issue.

Ok that's starting to get nasty. Can you please test what happens when you
boot with drm.vblankoffdelay=0 and whether drm.vblankoffdelay=1000 has an
effect on reproduction rate? No debug output needed.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch