linux-kernel - Re: WARNING: CPU: 0 PID: 3634 at drivers/gpu/drm/drm_irq.c:1141 drm_wait_one

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Message-ID: <20150708073218.GA7568@phenom.ffwll.local>
Date:	Wed, 8 Jul 2015 09:32:18 +0200
From:	Daniel Vetter <daniel@...ll.ch>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	Daniel Vetter <daniel@...ll.ch>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
	Ander Conselvan de Oliveira 
	<ander.conselvan.de.oliveira@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	dri-devel@...ts.freedesktop.org,
	"intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
	"Roper, Matthew D" <matthew.d.roper@...el.com>
Subject: Re: WARNING: CPU: 0 PID: 3634 at drivers/gpu/drm/drm_irq.c:1141
 drm_wait_one_vblank

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
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