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@xxxxxxxx>
Date: Thu Apr 11 14:26:55 2013 +0000
drm/fb-helper: Fix locking in drm_fb_helper_hotplug_event
Driver's and ->fill_modes functions are allowed to grab crtc mutexes
(for e.g. load detect). Hence we need to first only grab the general
kms mutex, and only in a second step grab all locks to do the
modesets.
This prevents a deadlock on my gm45 in the tv load detect code called
by drm_helper_probe_single_connector_modes.
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Signed-off-by: Dave Airlie <airlied@xxxxxxxxxx>
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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