drm: don't check modeset locks in panic handler

commit a9b054e8 upstream.

Since we know that locking is broken in that case and it's more
important to not flood the dmesg with random gunk.
Reported-and-tested-by: Borislav Petkov <bp@suse.de>
References: http://lkml.kernel.org/r/20130502000206.GH15623@pd.tnic
Cc: Dave Airlie <airlied@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpu/drm/drm_crtc.c

@@ -78,6 +78,10 @@ void drm_warn_on_modeset_not_all_locked(struct drm_device *dev)
 {
 	struct drm_crtc *crtc;
 
+	/* Locking is currently fubar in the panic handler. */
+	if (oops_in_progress)
+		return;
+
 	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head)
 		WARN_ON(!mutex_is_locked(&crtc->mutex));