Comment 7 for bug 568138

It just occurred gain, this time with a different backtrace:

[ 4350.545525] INFO: task i915:308 blocked for more than 120 seconds.
[ 4350.545529] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 4350.545533] i915 D 00000000ffffffff 0 308 2 0x00000000
[ 4350.545539] ffff88022e105d40 0000000000000046 0000000000015bc0 0000000000015bc0
[ 4350.545545] ffff88022f595f80 ffff88022e105fd8 0000000000015bc0 ffff88022f595bc0
[ 4350.545550] 0000000000015bc0 ffff88022e105fd8 0000000000015bc0 ffff88022f595f80
[ 4350.545555] Call Trace:
[ 4350.545568] [<ffffffff8153f897>] __mutex_lock_slowpath+0xe7/0x170
[ 4350.545576] [<ffffffff81058620>] ? finish_task_switch+0x50/0xe0
[ 4350.545580] [<ffffffff8153f78b>] mutex_lock+0x2b/0x50
[ 4350.545617] [<ffffffffa00c337d>] i915_gem_retire_work_handler+0x3d/0xa0 [i915]
[ 4350.545635] [<ffffffffa00c3340>] ? i915_gem_retire_work_handler+0x0/0xa0 [i915]
[ 4350.545643] [<ffffffff81080777>] run_workqueue+0xc7/0x1a0
[ 4350.545647] [<ffffffff810808f3>] worker_thread+0xa3/0x110
[ 4350.545653] [<ffffffff81085320>] ? autoremove_wake_function+0x0/0x40
[ 4350.545657] [<ffffffff81080850>] ? worker_thread+0x0/0x110
[ 4350.545661] [<ffffffff81084fa6>] kthread+0x96/0xa0
[ 4350.545667] [<ffffffff810141ea>] child_rip+0xa/0x20
[ 4350.545671] [<ffffffff81084f10>] ? kthread+0x0/0xa0
[ 4350.545674] [<ffffffff810141e0>] ? child_rip+0x0/0x20
[ 4350.545694] INFO: task Xorg:1316 blocked for more than 120 seconds.
[ 4350.545696] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 4350.545699] Xorg D 0000000000000000 0 1316 1235 0x00400004
[ 4350.545703] ffff88020c4a7cb8 0000000000000086 0000000000015bc0 0000000000015bc0
[ 4350.545708] ffff88020c411ab0 ffff88020c4a7fd8 0000000000015bc0 ffff88020c4116f0
[ 4350.545713] 0000000000015bc0 ffff88020c4a7fd8 0000000000015bc0 ffff88020c411ab0
[ 4350.545717] Call Trace:
[ 4350.545722] [<ffffffff8153f897>] __mutex_lock_slowpath+0xe7/0x170
[ 4350.545726] [<ffffffff8153f78b>] mutex_lock+0x2b/0x50
[ 4350.545742] [<ffffffffa00c2e36>] i915_gem_busy_ioctl+0x46/0xd0 [i915]
[ 4350.545757] [<ffffffffa002de2a>] drm_ioctl+0x27a/0x480 [drm]
[ 4350.545771] [<ffffffffa00c2df0>] ? i915_gem_busy_ioctl+0x0/0xd0 [i915]
[ 4350.545776] [<ffffffff81088432>] ? enqueue_hrtimer+0x82/0xd0
[ 4350.545782] [<ffffffff810893b9>] ? __hrtimer_start_range_ns+0x189/0x400
[ 4350.545788] [<ffffffff81152a92>] vfs_ioctl+0x22/0xa0
[ 4350.545793] [<ffffffff81152d41>] do_vfs_ioctl+0x81/0x380
[ 4350.545797] [<ffffffff811530c1>] sys_ioctl+0x81/0xa0
[ 4350.545802] [<ffffffff810131b2>] system_call_fastpath+0x16/0x1b

Full dmesg attached.