Comment 6 for bug 946899

Experiencing this problem on Ubuntu 12.04 (linux-3.2.0-24-generic) without nolapic boot option though. When the error happens, a prior mouse hang of several seconds is a sure sign, the tft gets dark and restores, gets dark and restores, then graphics acceleration appears disabled, font displayed with faults and I have to log out and log in. The problem seems to be gone in the new kde session with desktop effects on ... until I boot anew.

 My dmesg succeeding the error is:

[ 63.965111] [<ffffffff8106712f>] warn_slowpath_common+0x7f/0xc0
[ 63.965112] [<ffffffff8106718a>] warn_slowpath_null+0x1a/0x20
[ 63.965116] [<ffffffffa00779e4>] __gen6_gt_wait_for_fifo+0x94/0xa0 [i915]
[ 63.965121] [<ffffffffa0078065>] i915_write32+0xe5/0xf0 [i915]
[ 63.965126] [<ffffffffa00b4752>] gen6_ring_put_irq+0xa2/0xc0 [i915]
[ 63.965131] [<ffffffffa00b47c8>] gen6_render_ring_put_irq+0x18/0x20 [i915]
[ 63.965136] [<ffffffffa0089ba7>] i915_wait_request+0x1b7/0x560 [i915]
[ 63.965138] [<ffffffff8108aec0>] ? add_wait_queue+0x60/0x60
[ 63.965143] [<ffffffffa0089f82>] i915_gem_object_wait_rendering+0x32/0x40 [i
915]
[ 63.965148] [<ffffffffa008ed3d>] i915_gem_execbuffer_sync_rings+0xdd/0x160 [
i915]
[ 63.965153] [<ffffffffa008ef2e>] i915_gem_execbuffer_move_to_gpu+0x16e/0x200
 [i915]
[ 63.965157] [<ffffffffa008f65b>] i915_gem_do_execbuffer.isra.8+0x69b/0x940 [
i915]
[ 63.965163] [<ffffffffa009f349>] ? intel_mark_busy+0xd9/0x110 [i915]
[ 63.965168] [<ffffffffa008fdc3>] i915_gem_execbuffer2+0xa3/0x270 [i915]
[ 63.965172] [<ffffffffa00165d4>] drm_ioctl+0x444/0x510 [drm]
[ 63.965177] [<ffffffffa008fd20>] ? i915_gem_execbuffer+0x420/0x420 [i915]
[ 63.965179] [<ffffffff8101dbd4>] ? restore_user_xstate+0x54/0xa0
[ 63.965181] [<ffffffff81189cfa>] do_vfs_ioctl+0x8a/0x340
[ 63.965183] [<ffffffff8118a041>] sys_ioctl+0x91/0xa0
[ 63.965185] [<ffffffff81664a82>] system_call_fastpath+0x16/0x1b
[ 63.965186] ---[ end trace 20690ee302d12d8d ]---
[ 68.296329] [drm:i915_hangcheck_elapsed] *ERROR* Hangcheck timer elapsed... GPU hung
[ 68.297855] [drm] capturing error event; look for more information in /debug/dri/0/i915_error_state
[ 68.311854] [drm:i915_wait_request] *ERROR* i915_wait_request returns -11 (awaiting 11846 at 11845, next 11847)
[ 68.315568] [drm:init_ring_common] *ERROR* render ring initialization failed ctl 00000000 head 00000000 tail 00000000 start 00000000
[ 68.319138] [drm:init_ring_common] *ERROR* gen6 bsd ring initialization failed ctl 00000000 head 00000000 tail 00000000 start 00000000
[ 68.322179] [drm:init_ring_common] *ERROR* blt ring initialization failed ctl 00000000 head 00000000 tail 00000000 start 00000000
[ 70.159916] [drm:i915_hangcheck_elapsed] *ERROR* Hangcheck timer elapsed... GPU hung
[ 70.161991] [drm:i915_wait_request] *ERROR* i915_wait_request returns -11 (awaiting 11847 at 11844, next 11848)
[ 70.162096] [drm:i915_reset] *ERROR* GPU hanging too fast, declaring wedged!
[ 70.162100] [drm:i915_reset] *ERROR* Failed to reset chip.