From 1b1d5397058f06bc5bd87d43ed93f34b28546ea4 Mon Sep 17 00:00:00 2001 From: Daniel Vetter <daniel.vetter@ffwll.ch> Date: Thu, 24 Jan 2013 16:42:07 +0100 Subject: [PATCH] drm/fb-helper: don't sleep for screen unblank when an oopps is in progress Otherwise the system will burn even brighter and worse, leave the user wondering what's going on exactly. Since we already have a panic handler which will (try) to restore the entire fbdev console mode, we can just bail out. Inspired by a patch from Konstantin Khlebnikov. The callchain leading to this, cut&pasted from Konstantin's original patch: callstack: panic() bust_spinlocks(1) unblank_screen() vc->vc_sw->con_blank() fbcon_blank() fb_blank() info->fbops->fb_blank() drm_fb_helper_blank() drm_fb_helper_dpms() drm_modeset_lock_all() mutex_lock(&dev->mode_config.mutex) Note that the entire locking in the fb helper around panic/sysrq and kdbg is ... non-existant. So we have a decent change of blowing up everything. But since reworking this ties in with funny concepts like the fbdev notifier chain or the impressive things which happen around console_lock while oopsing, I'll leave that as an exercise for braver souls than me. v2: Drop the -EBUSY return value I've copied, we don't need it since the we'll take care of things ourselves anyway. Cc: Konstantin Khlebnikov <khlebnikov@openvz.org> Cc: Andrew Morton <akpm@linux-foundation.org> References: https://patchwork.kernel.org/patch/1878181/ Reviewed-by: Rob Clark <robdclark@gmail.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> --- drivers/gpu/drm/drm_fb_helper.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index 94f304d8b7955..59d6b9bf204bb 100644 --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -390,6 +390,14 @@ static void drm_fb_helper_dpms(struct fb_info *info, int dpms_mode) struct drm_connector *connector; int i, j; + /* + * fbdev->blank can be called from irq context in case of a panic. + * Since we already have our own special panic handler which will + * restore the fbdev console mode completely, just bail out early. + */ + if (oops_in_progress) + return; + /* * For each CRTC in this fb, turn the connectors on/off. */ -- GitLab