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

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Date:	Wed, 1 Jul 2015 10:26:39 +0200
From:	Daniel Vetter <daniel@...ll.ch>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	Daniel Vetter <daniel@...ll.ch>, David Airlie <airlied@...ux.ie>,
	dri-devel@...ts.freedesktop.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: WARNING: CPU: 0 PID: 3634 at drivers/gpu/drm/drm_irq.c:1141
 drm_wait_one_vblank

On Tue, Jun 30, 2015 at 10:13:35PM +0200, Michal Hocko wrote:
> On Tue 30-06-15 18:59:29, Daniel Vetter wrote:
> [...]
> > I looked at dmesg, nothing out of the ordinary there. Unfortunately also
> > no hints why the pipe is somehow off when we think it's on. Can you please
> > test the below patch and grab a new dmesg?
> 
> Attached.

I'm still baffled - looking at the code intel_crtc->active should be set,
but somehow the real hw pipe is dead. Or at least we don't get a vblank
irq for it somehow. Confusing.

> > Also it might be time to start bisecting this if you can readily reproduce it.
> 
> Yes, I can reproduce it just by switching to the text console. Sometimes
> it is the first attempt already but sometimes it takes several attempts.
> I will try to go back to 4.0 and bisect it then.

Yes please do, since this is a confusing regression I think the bisect
result will be the fastest way forward.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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