From b77f0765fdfb3a115e40effd890acb4674dc0989 Mon Sep 17 00:00:00 2001 From: Thierry Reding Date: Tue, 29 Apr 2014 11:44:32 +0200 Subject: [PATCH] drm: Try to acquire modeset lock on panic or sysrq Commit 62ff94a54921 "drm/crtc-helper: remove LOCKING from kerneldoc" causes drm_helper_crtc_in_use() and drm_helper_encoder_in_use() to complain loudly during a kernel panic or sysrq processing. This is caused by nobody acquiring the modeset lock in these code paths. This patch fixes this by trying to acquire the modeset lock for each FB helper that's forced to kernel mode. If the lock can't be acquired, it's likely that somebody else is performing a modeset. However, doing another modeset concurrently might make things even worse, so the safe option is to simply bail out in that case. Reviewed-by: Daniel Vetter Reviewed-by: David Herrmann Signed-off-by: Thierry Reding Signed-off-by: Daniel Vetter --- drivers/gpu/drm/drm_fb_helper.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index 04d3fd3658f3..158d8e51db3d 100644 --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -326,12 +326,21 @@ static bool drm_fb_helper_force_kernel_mode(void) return false; list_for_each_entry(helper, &kernel_fb_helper_list, kernel_fb_list) { - if (helper->dev->switch_power_state == DRM_SWITCH_POWER_OFF) + struct drm_device *dev = helper->dev; + + if (dev->switch_power_state == DRM_SWITCH_POWER_OFF) + continue; + + if (!mutex_trylock(&dev->mode_config.mutex)) { + error = true; continue; + } ret = drm_fb_helper_restore_fbdev_mode(helper); if (ret) error = true; + + mutex_unlock(&dev->mode_config.mutex); } return error; } -- 2.45.2