From: Chris Wilson Date: Fri, 22 Apr 2011 10:03:57 +0000 (+0100) Subject: drm: Take lock around probes for drm_fb_helper_hotplug_event X-Git-Tag: v2.6.39~20^2 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=752d2635ebb12b6122ba05775f7d1ccfef14b275;p=pandora-kernel.git drm: Take lock around probes for drm_fb_helper_hotplug_event We need to hold the dev->mode_config.mutex whilst detecting the output status. But we also need to drop it for the call into drm_fb_helper_single_fb_probe(), which indirectly acquires the lock when attaching the fbcon. Failure to do so exposes a race with normal output probing. Detected by adding some warnings that the mutex is held to the backend detect routines: [ 17.772456] WARNING: at drivers/gpu/drm/i915/intel_crt.c:471 intel_crt_detect+0x3e/0x373 [i915]() [ 17.772458] Hardware name: Latitude E6400 [ 17.772460] Modules linked in: .... [ 17.772582] Pid: 11, comm: kworker/0:1 Tainted: G W 2.6.38.4-custom.2 #8 [ 17.772584] Call Trace: [ 17.772591] [] ? warn_slowpath_common+0x78/0x8c [ 17.772603] [] ? intel_crt_detect+0x3e/0x373 [i915] [ 17.772612] [] ? drm_helper_probe_single_connector_modes+0xbf/0x2af [drm_kms_helper] [ 17.772619] [] ? drm_fb_helper_probe_connector_modes+0x39/0x4d [drm_kms_helper] [ 17.772625] [] ? drm_fb_helper_hotplug_event+0xa5/0xc3 [drm_kms_helper] [ 17.772633] [] ? output_poll_execute+0x146/0x17c [drm_kms_helper] [ 17.772638] [] ? cfq_init_queue+0x247/0x345 [ 17.772644] [] ? output_poll_execute+0x0/0x17c [drm_kms_helper] [ 17.772648] [] ? process_one_work+0x193/0x28e [ 17.772652] [] ? worker_thread+0xef/0x172 [ 17.772655] [] ? worker_thread+0x0/0x172 [ 17.772658] [] ? worker_thread+0x0/0x172 [ 17.772663] [] ? kthread+0x7a/0x82 [ 17.772668] [] ? kernel_thread_helper+0x4/0x10 [ 17.772671] [] ? kthread+0x0/0x82 [ 17.772674] [] ? kernel_thread_helper+0x0/0x10 Reported-by: Frederik Himpe References: https://bugs.freedesktop.org/show_bug.cgi?id=36394 Signed-off-by: Chris Wilson Signed-off-by: Dave Airlie --- Reading git-diff-tree failed