linux-kernel - Re: drm: i915+fb: crtc->lock recursive locking deadlock on VT switch [>= 3.9-rc1 regresion]

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Date:	Sun, 14 Apr 2013 08:47:07 +0200
From:	Krzysztof Mazur <krzysiek@...lesie.net>
To:	Chris Wilson <chris@...is-wilson.co.uk>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	airlied@...ux.ie, daniel.vetter@...ll.ch
Subject: Re: drm: i915+fb: crtc->lock recursive locking deadlock on VT switch
 [>= 3.9-rc1 regresion]

On Sat, Apr 13, 2013 at 06:10:40PM +0100, Chris Wilson wrote:
> On Sat, Apr 13, 2013 at 05:41:46PM +0200, Krzysztof Mazur wrote:
> > Hi,
> > 
> > the drm_fb_helper_hotplug_event() locks all crtc->mutex locks by calling
> > drm_modeset_lock_all() and later calls drm_fb_helper_probe_connector_modes(),
> > which in case of i915 DRM driver effectively calls
> > intel_get_load_detect_pipe() that tries to lock crtc->mutex again.
> > This causes a deadlock, and can be in some cases triggered by VT
> > switch to framebuffer console on i915.
> > 
> > This bug is introduced in Linux 3.9-rc1 and still exists
> > in v3.9-rc6-183-gbf81710. Linux 3.8 is ok.
> 
> In Dave's drm-fixes branch:
> 
> commit 89ced125472b8551c65526934b7f6c733a6864fa
> Author: Daniel Vetter <daniel.vetter@...ll.ch>
> Date:   Thu Apr 11 14:26:55 2013 +0000
> 
>     drm/fb-helper: Fix locking in drm_fb_helper_hotplug_event

Yes, this patch fixes the problem.

Thanks,
Krzysiek
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