With Max's new rsyslog functionality, I've gotten a stack trace out of the 2013-02-04 build.

2013-02-15T20:19:39+00:00 acer-veriton-04 kernel: [  849.324073] INFO: task Xorg:5083 blocked for more than 120 seconds.
2013-02-15T20:19:39+00:00 acer-veriton-04 kernel: [  849.324081] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
2013-02-15T20:19:39+00:00 acer-veriton-04 kernel: [  849.324086] Xorg            D ffff88007e293f40     0  5083   3871 0x00400000
2013-02-15T20:19:39+00:00 acer-veriton-04 kernel: [  849.324094]  ffff8800780e7c58 0000000000000046 ffff880075661740 ffff8800780e7fd8
2013-02-15T20:19:39+00:00 acer-veriton-04 kernel: [  849.324103]  ffff8800780e7fd8 ffff8800780e7fd8 ffff88007ac21740 ffff880075661740
2013-02-15T20:19:39+00:00 acer-veriton-04 kernel: [  849.324110]  ffff8800725e3800 ffff8800770ae268 ffff8800725e0000 0000000000000000
2013-02-15T20:19:39+00:00 acer-veriton-04 kernel: [  849.324118] Call Trace:
2013-02-15T20:19:39+00:00 acer-veriton-04 kernel: [  849.324133]  [<ffffffff816c6e79>] schedule+0x29/0x70
2013-02-15T20:19:39+00:00 acer-veriton-04 kernel: [  849.324190]  [<ffffffffa00a02e5>] intel_crtc_wait_for_pending_flips+0x75/0xd0 [i915]
2013-02-15T20:19:39+00:00 acer-veriton-04 kernel: [  849.324199]  [<ffffffff8107dc00>] ? finish_wait+0x80/0x80
2013-02-15T20:19:39+00:00 acer-veriton-04 kernel: [  849.324232]  [<ffffffffa00a2d67>] i9xx_crtc_disable+0x87/0x180 [i915]
2013-02-15T20:19:39+00:00 acer-veriton-04 kernel: [  849.324266]  [<ffffffffa00a7baf>] intel_crtc_update_dpms+0x6f/0xa0 [i915]
2013-02-15T20:19:39+00:00 acer-veriton-04 kernel: [  849.324299]  [<ffffffffa00adc47>] intel_crt_dpms+0x77/0xc0 [i915]
2013-02-15T20:19:39+00:00 acer-veriton-04 kernel: [  849.324331]  [<ffffffffa00159b0>] drm_mode_obj_set_property_ioctl+0x330/0x340 [drm]
2013-02-15T20:19:39+00:00 acer-veriton-04 kernel: [  849.324358]  [<ffffffffa00159f0>] drm_mode_connector_property_set_ioctl+0x30/0x40 [drm]
2013-02-15T20:19:39+00:00 acer-veriton-04 kernel: [  849.324382]  [<ffffffffa0004559>] drm_ioctl+0x4e9/0x5b0 [drm]
2013-02-15T20:19:39+00:00 acer-veriton-04 kernel: [  849.324411]  [<ffffffffa00159c0>] ? drm_mode_obj_set_property_ioctl+0x340/0x340 [drm]
2013-02-15T20:19:39+00:00 acer-veriton-04 kernel: [  849.324419]  [<ffffffff81085bf8>] ? lg_global_unlock+0x48/0x60
2013-02-15T20:19:39+00:00 acer-veriton-04 kernel: [  849.324427]  [<ffffffff811a52a9>] do_vfs_ioctl+0x99/0x570
2013-02-15T20:19:39+00:00 acer-veriton-04 kernel: [  849.324435]  [<ffffffff8106be9b>] ? recalc_sigpending+0x1b/0x60
2013-02-15T20:19:39+00:00 acer-veriton-04 kernel: [  849.324442]  [<ffffffff8106c7b7>] ? __set_task_blocked+0x37/0x80
2013-02-15T20:19:39+00:00 acer-veriton-04 kernel: [  849.324449]  [<ffffffff811a5811>] sys_ioctl+0x91/0xb0
2013-02-15T20:19:39+00:00 acer-veriton-04 kernel: [  849.324458]  [<ffffffff816d06dd>] system_call_fastpath+0x1a/0x1f
2013-02-15T20:21:39+00:00 acer-veriton-04 kernel: [  969.324076] INFO: task Xorg:5083 blocked for more than 120 seconds.
2013-02-15T20:21:39+00:00 acer-veriton-04 kernel: [  969.324084] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
2013-02-15T20:21:39+00:00 acer-veriton-04 kernel: [  969.324089] Xorg            D ffff88007e293f40     0  5083   3871 0x00400000
2013-02-15T20:21:39+00:00 acer-veriton-04 kernel: [  969.324097]  ffff8800780e7c58 0000000000000046 ffff880075661740 ffff8800780e7fd8
2013-02-15T20:21:39+00:00 acer-veriton-04 kernel: [  969.324106]  ffff8800780e7fd8 ffff8800780e7fd8 ffff88007ac21740 ffff880075661740
2013-02-15T20:21:39+00:00 acer-veriton-04 kernel: [  969.324113]  ffff8800725e3800 ffff8800770ae268 ffff8800725e0000 0000000000000000
2013-02-15T20:21:39+00:00 acer-veriton-04 kernel: [  969.324121] Call Trace:
2013-02-15T20:21:39+00:00 acer-veriton-04 kernel: [  969.324136]  [<ffffffff816c6e79>] schedule+0x29/0x70
2013-02-15T20:21:39+00:00 acer-veriton-04 kernel: [  969.324193]  [<ffffffffa00a02e5>] intel_crtc_wait_for_pending_flips+0x75/0xd0 [i915]
2013-02-15T20:21:39+00:00 acer-veriton-04 kernel: [  969.324202]  [<ffffffff8107dc00>] ? finish_wait+0x80/0x80
2013-02-15T20:21:39+00:00 acer-veriton-04 kernel: [  969.324235]  [<ffffffffa00a2d67>] i9xx_crtc_disable+0x87/0x180 [i915]
2013-02-15T20:21:39+00:00 acer-veriton-04 kernel: [  969.324269]  [<ffffffffa00a7baf>] intel_crtc_update_dpms+0x6f/0xa0 [i915]
2013-02-15T20:21:39+00:00 acer-veriton-04 kernel: [  969.324302]  [<ffffffffa00adc47>] intel_crt_dpms+0x77/0xc0 [i915]
2013-02-15T20:21:39+00:00 acer-veriton-04 kernel: [  969.324334]  [<ffffffffa00159b0>] drm_mode_obj_set_property_ioctl+0x330/0x340 [drm]
2013-02-15T20:21:39+00:00 acer-veriton-04 kernel: [  969.324361]  [<ffffffffa00159f0>] drm_mode_connector_property_set_ioctl+0x30/0x40 [drm]
2013-02-15T20:21:39+00:00 acer-veriton-04 kernel: [  969.324385]  [<ffffffffa0004559>] drm_ioctl+0x4e9/0x5b0 [drm]
2013-02-15T20:21:39+00:00 acer-veriton-04 kernel: [  969.324414]  [<ffffffffa00159c0>] ? drm_mode_obj_set_property_ioctl+0x340/0x340 [drm]
2013-02-15T20:21:39+00:00 acer-veriton-04 kernel: [  969.324422]  [<ffffffff81085bf8>] ? lg_global_unlock+0x48/0x60
2013-02-15T20:21:39+00:00 acer-veriton-04 kernel: [  969.324430]  [<ffffffff811a52a9>] do_vfs_ioctl+0x99/0x570
2013-02-15T20:21:39+00:00 acer-veriton-04 kernel: [  969.324438]  [<ffffffff8106be9b>] ? recalc_sigpending+0x1b/0x60
2013-02-15T20:21:39+00:00 acer-veriton-04 kernel: [  969.324446]  [<ffffffff8106c7b7>] ? __set_task_blocked+0x37/0x80
2013-02-15T20:21:39+00:00 acer-veriton-04 kernel: [  969.324453]  [<ffffffff811a5811>] sys_ioctl+0x91/0xb0
2013-02-15T20:21:39+00:00 acer-veriton-04 kernel: [  969.324461]  [<ffffffff816d06dd>] system_call_fastpath+0x1a/0x1f
2013-02-15T20:23:39+00:00 acer-veriton-04 kernel: [ 1089.324074] INFO: task Xorg:5083 blocked for more than 120 seconds.
2013-02-15T20:23:39+00:00 acer-veriton-04 kernel: [ 1089.324082] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
2013-02-15T20:23:39+00:00 acer-veriton-04 kernel: [ 1089.324087] Xorg            D ffff88007e293f40     0  5083   3871 0x00400000
2013-02-15T20:23:39+00:00 acer-veriton-04 kernel: [ 1089.324096]  ffff8800780e7c58 0000000000000046 ffff880075661740 ffff8800780e7fd8
2013-02-15T20:23:39+00:00 acer-veriton-04 kernel: [ 1089.324104]  ffff8800780e7fd8 ffff8800780e7fd8 ffff88007ac21740 ffff880075661740
2013-02-15T20:23:39+00:00 acer-veriton-04 kernel: [ 1089.324112]  ffff8800725e3800 ffff8800770ae268 ffff8800725e0000 0000000000000000
2013-02-15T20:23:39+00:00 acer-veriton-04 kernel: [ 1089.324120] Call Trace:
2013-02-15T20:23:39+00:00 acer-veriton-04 kernel: [ 1089.324135]  [<ffffffff816c6e79>] schedule+0x29/0x70
2013-02-15T20:23:39+00:00 acer-veriton-04 kernel: [ 1089.324192]  [<ffffffffa00a02e5>] intel_crtc_wait_for_pending_flips+0x75/0xd0 [i915]
2013-02-15T20:23:39+00:00 acer-veriton-04 kernel: [ 1089.324201]  [<ffffffff8107dc00>] ? finish_wait+0x80/0x80
2013-02-15T20:23:39+00:00 acer-veriton-04 kernel: [ 1089.324234]  [<ffffffffa00a2d67>] i9xx_crtc_disable+0x87/0x180 [i915]
2013-02-15T20:23:39+00:00 acer-veriton-04 kernel: [ 1089.324268]  [<ffffffffa00a7baf>] intel_crtc_update_dpms+0x6f/0xa0 [i915]
2013-02-15T20:23:39+00:00 acer-veriton-04 kernel: [ 1089.324301]  [<ffffffffa00adc47>] intel_crt_dpms+0x77/0xc0 [i915]
2013-02-15T20:23:39+00:00 acer-veriton-04 kernel: [ 1089.324333]  [<ffffffffa00159b0>] drm_mode_obj_set_property_ioctl+0x330/0x340 [drm]
2013-02-15T20:23:39+00:00 acer-veriton-04 kernel: [ 1089.324360]  [<ffffffffa00159f0>] drm_mode_connector_property_set_ioctl+0x30/0x40 [drm]
2013-02-15T20:23:39+00:00 acer-veriton-04 kernel: [ 1089.324383]  [<ffffffffa0004559>] drm_ioctl+0x4e9/0x5b0 [drm]
2013-02-15T20:23:39+00:00 acer-veriton-04 kernel: [ 1089.324412]  [<ffffffffa00159c0>] ? drm_mode_obj_set_property_ioctl+0x340/0x340 [drm]
2013-02-15T20:23:39+00:00 acer-veriton-04 kernel: [ 1089.324420]  [<ffffffff81085bf8>] ? lg_global_unlock+0x48/0x60
2013-02-15T20:23:39+00:00 acer-veriton-04 kernel: [ 1089.324429]  [<ffffffff811a52a9>] do_vfs_ioctl+0x99/0x570
2013-02-15T20:23:39+00:00 acer-veriton-04 kernel: [ 1089.324437]  [<ffffffff8106be9b>] ? recalc_sigpending+0x1b/0x60
2013-02-15T20:23:39+00:00 acer-veriton-04 kernel: [ 1089.324444]  [<ffffffff8106c7b7>] ? __set_task_blocked+0x37/0x80
2013-02-15T20:23:39+00:00 acer-veriton-04 kernel: [ 1089.324451]  [<ffffffff811a5811>] sys_ioctl+0x91/0xb0
2013-02-15T20:23:39+00:00 acer-veriton-04 kernel: [ 1089.324459]  [<ffffffff816d06dd>] system_call_fastpath+0x1a/0x1f
2013-02-15T20:25:39+00:00 acer-veriton-04 kernel: [ 1209.324074] INFO: task Xorg:5083 blocked for more than 120 seconds.
2013-02-15T20:25:39+00:00 acer-veriton-04 kernel: [ 1209.324082] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
2013-02-15T20:25:39+00:00 acer-veriton-04 kernel: [ 1209.324087] Xorg            D ffff88007e293f40     0  5083   3871 0x00400000
2013-02-15T20:25:39+00:00 acer-veriton-04 kernel: [ 1209.324096]  ffff8800780e7c58 0000000000000046 ffff880075661740 ffff8800780e7fd8
2013-02-15T20:25:39+00:00 acer-veriton-04 kernel: [ 1209.324104]  ffff8800780e7fd8 ffff8800780e7fd8 ffff88007ac21740 ffff880075661740
2013-02-15T20:25:39+00:00 acer-veriton-04 kernel: [ 1209.324112]  ffff8800725e3800 ffff8800770ae268 ffff8800725e0000 0000000000000000
2013-02-15T20:25:39+00:00 acer-veriton-04 kernel: [ 1209.324120] Call Trace:
2013-02-15T20:25:39+00:00 acer-veriton-04 kernel: [ 1209.324135]  [<ffffffff816c6e79>] schedule+0x29/0x70
2013-02-15T20:25:39+00:00 acer-veriton-04 kernel: [ 1209.324192]  [<ffffffffa00a02e5>] intel_crtc_wait_for_pending_flips+0x75/0xd0 [i915]
2013-02-15T20:25:39+00:00 acer-veriton-04 kernel: [ 1209.324201]  [<ffffffff8107dc00>] ? finish_wait+0x80/0x80
2013-02-15T20:25:39+00:00 acer-veriton-04 kernel: [ 1209.324234]  [<ffffffffa00a2d67>] i9xx_crtc_disable+0x87/0x180 [i915]
2013-02-15T20:25:39+00:00 acer-veriton-04 kernel: [ 1209.324268]  [<ffffffffa00a7baf>] intel_crtc_update_dpms+0x6f/0xa0 [i915]
2013-02-15T20:25:39+00:00 acer-veriton-04 kernel: [ 1209.324301]  [<ffffffffa00adc47>] intel_crt_dpms+0x77/0xc0 [i915]
2013-02-15T20:25:39+00:00 acer-veriton-04 kernel: [ 1209.324333]  [<ffffffffa00159b0>] drm_mode_obj_set_property_ioctl+0x330/0x340 [drm]
2013-02-15T20:25:39+00:00 acer-veriton-04 kernel: [ 1209.324360]  [<ffffffffa00159f0>] drm_mode_connector_property_set_ioctl+0x30/0x40 [drm]
2013-02-15T20:25:39+00:00 acer-veriton-04 kernel: [ 1209.324384]  [<ffffffffa0004559>] drm_ioctl+0x4e9/0x5b0 [drm]
2013-02-15T20:25:39+00:00 acer-veriton-04 kernel: [ 1209.324413]  [<ffffffffa00159c0>] ? drm_mode_obj_set_property_ioctl+0x340/0x340 [drm]
2013-02-15T20:25:39+00:00 acer-veriton-04 kernel: [ 1209.324421]  [<ffffffff81085bf8>] ? lg_global_unlock+0x48/0x60
2013-02-15T20:25:39+00:00 acer-veriton-04 kernel: [ 1209.324429]  [<ffffffff811a52a9>] do_vfs_ioctl+0x99/0x570
2013-02-15T20:25:39+00:00 acer-veriton-04 kernel: [ 1209.324437]  [<ffffffff8106be9b>] ? recalc_sigpending+0x1b/0x60
2013-02-15T20:25:39+00:00 acer-veriton-04 kernel: [ 1209.324445]  [<ffffffff8106c7b7>] ? __set_task_blocked+0x37/0x80
2013-02-15T20:25:39+00:00 acer-veriton-04 kernel: [ 1209.324451]  [<ffffffff811a5811>] sys_ioctl+0x91/0xb0
2013-02-15T20:25:39+00:00 acer-veriton-04 kernel: [ 1209.324460]  [<ffffffff816d06dd>] system_call_fastpath+0x1a/0x1f