Hello! Below is my patch for drm. Here is a photo of kernel output I had: http://s17.postimg.org/k0301hgf3/Untitled.jpg to illustrate what I am writing in the description.

--- Subject: [PATCH] drm/crtc-helper: skip locking checks in panicking path

Skip locking checks in drm_helper_*_in_use() if they are called in panicking path. See similar code in drm_warn_on_modeset_not_all_locked().

After panic information has been output, these WARN_ONs go off outputing a lot of lines and scrolling the panic information out of the screen. Here is a partial call trace showing how execution reaches them:

? drm_helper_crtc_in_use() ? __drm_helper_disable_unused_functions() ? several *_set_config functions ? drm_fb_helper_restore_fbdev_mode()

Cc: Dave Airlie airlied@redhat.com Cc: Daniel Vetter daniel.vetter@ffwll.ch Signed-off-by: Sergei Antonov saproj@gmail.com --- drivers/gpu/drm/drm_crtc_helper.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_crtc_helper.c b/drivers/gpu/drm/drm_crtc_helper.c index df281b5..872ba11 100644 --- a/drivers/gpu/drm/drm_crtc_helper.c +++ b/drivers/gpu/drm/drm_crtc_helper.c @@ -29,6 +29,7 @@ * Jesse Barnes jesse.barnes@intel.com */

+#include <linux/kernel.h> #include <linux/export.h> #include <linux/moduleparam.h>

@@ -88,7 +89,13 @@ bool drm_helper_encoder_in_use(struct drm_encoder *encoder) struct drm_connector *connector; struct drm_device *dev = encoder->dev;

- WARN_ON(!mutex_is_locked(&dev->mode_config.mutex)); + /* + * We can expect this mutex to be locked if we are not panicking. + * Locking is currently fubar in the panic handler. + */ + if (!oops_in_progress) + WARN_ON(!mutex_is_locked(&dev->mode_config.mutex)); + list_for_each_entry(connector, &dev->mode_config.connector_list, head) if (connector->encoder == encoder) return true; @@ -112,7 +119,13 @@ bool drm_helper_crtc_in_use(struct drm_crtc *crtc) struct drm_encoder *encoder; struct drm_device *dev = crtc->dev;

- WARN_ON(!mutex_is_locked(&dev->mode_config.mutex)); + /* + * We can expect this mutex to be locked if we are not panicking. + * Locking is currently fubar in the panic handler. + */ + if (!oops_in_progress) + WARN_ON(!mutex_is_locked(&dev->mode_config.mutex)); + list_for_each_entry(encoder, &dev->mode_config.encoder_list, head) if (encoder->crtc == crtc && drm_helper_encoder_in_use(encoder)) return true;