Comment 2 for bug 606376

When this problem happens, I get this in syslog:
---8<---
Jul 18 10:11:23 sepiroth kernel: [31932.235286] video LNXVIDEO:00: Restoring backlight state
Jul 18 10:11:23 sepiroth kernel: [31932.238066] BUG: unable to handle kernel NULL pointer dereference at (null)
Jul 18 10:11:23 sepiroth kernel: [31932.238074] IP: [<ffffffffa0276516>] render_ring_flush+0xa6/0x160 [i915]
Jul 18 10:11:23 sepiroth kernel: [31932.238098] PGD 784fb067 PUD 7815b067 PMD 0
Jul 18 10:11:23 sepiroth kernel: [31932.238103] Oops: 0002 [#2] SMP
Jul 18 10:11:23 sepiroth kernel: [31932.238107] last sysfs file: /sys/devices/pci0000:00/0000:00:1c.1/0000:03:00.0/ieee80211/phy0/rfkill1/uevent
Jul 18 10:11:23 sepiroth kernel: [31932.238111] CPU 0
Jul 18 10:11:23 sepiroth kernel: [31932.238112] Modules linked in: cryptd aes_x86_64 aes_generic hidp hid vboxnetadp vboxnetflt vboxdrv rfcomm sco parport_pc ppdev bridge stp bnep l2cap binfmt_misc snd_hda_codec_analog vga16fb vgastate joydev arc4 pcmcia snd_hda_intel snd_hda_codec snd_hwdep snd_pcm snd_seq_midi snd_rawmidi thinkpad_acpi snd_seq_midi_event snd_seq iwl3945 i915 snd_timer snd_seq_device iwlcore mac80211 drm_kms_helper btusb snd yenta_socket pcmcia_rsrc cfg80211 tpm_tis bluetooth led_class nvram drm pcmcia_core soundcore tpm tpm_bios psmouse serio_raw snd_page_alloc i2c_algo_bit video lp output parport intel_agp e1000e
Jul 18 10:11:23 sepiroth kernel: [31932.238161]
Jul 18 10:11:23 sepiroth kernel: [31932.238165] Pid: 1050, comm: Xorg Tainted: G D 2.6.35-7-generic #12-Ubuntu 88986DG/88986DG
Jul 18 10:11:23 sepiroth kernel: [31932.238168] RIP: 0010:[<ffffffffa0276516>] [<ffffffffa0276516>] render_ring_flush+0xa6/0x160 [i915]
Jul 18 10:11:23 sepiroth kernel: [31932.238181] RSP: 0018:ffff88007819fbe8 EFLAGS: 00010292
Jul 18 10:11:23 sepiroth kernel: [31932.238184] RAX: 0000000000000000 RBX: ffff8800702f0028 RCX: 0000000000000040
Jul 18 10:11:23 sepiroth kernel: [31932.238186] RDX: 0000000000000000 RSI: ffff8800702f0028 RDI: ffff8800702a1000
Jul 18 10:11:23 sepiroth kernel: [31932.238189] RBP: ffff88007819fc28 R08: 0000000000000000 R09: 0000000000000000
Jul 18 10:11:23 sepiroth kernel: [31932.238191] R10: ffff88007819e000 R11: ffff880000000000 R12: 0000000000000000
Jul 18 10:11:23 sepiroth kernel: [31932.238194] R13: ffff8800702a1000 R14: 0000000002000000 R15: 0000000000000001
Jul 18 10:11:23 sepiroth kernel: [31932.238197] FS: 00007fa63744b840(0000) GS:ffff880001e00000(0000) knlGS:0000000000000000
Jul 18 10:11:23 sepiroth kernel: [31932.238200] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Jul 18 10:11:23 sepiroth kernel: [31932.238202] CR2: 0000000000000000 CR3: 000000006f414000 CR4: 00000000000006f0
Jul 18 10:11:23 sepiroth kernel: [31932.238205] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
Jul 18 10:11:23 sepiroth kernel: [31932.238207] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Jul 18 10:11:23 sepiroth kernel: [31932.238210] Process Xorg (pid: 1050, threadinfo ffff88007819e000, task ffff88006fbdadc0)
Jul 18 10:11:23 sepiroth kernel: [31932.238212] Stack:
Jul 18 10:11:23 sepiroth kernel: [31932.238214] 000000000000027e 0000000000000040 ffff8800429fbe00 ffff8800702a1000
Jul 18 10:11:23 sepiroth kernel: [31932.238218] <0> ffff8800702f0000 0000000000000040 000000000000000a ffff88007819fde8
Jul 18 10:11:23 sepiroth kernel: [31932.238223] <0> ffff88007819fc58 ffffffffa0255bcb 0000000000000003 ffff8800429fbe00
Jul 18 10:11:23 sepiroth kernel: [31932.238228] Call Trace:
Jul 18 10:11:23 sepiroth kernel: [31932.238240] [<ffffffffa0255bcb>] i915_gem_flush+0x4b/0xa0 [i915]
Jul 18 10:11:23 sepiroth kernel: [31932.238252] [<ffffffffa025d117>] i915_gem_do_execbuffer+0xaf7/0xe50 [i915]
Jul 18 10:11:23 sepiroth kernel: [31932.238263] [<ffffffffa025d538>] i915_gem_execbuffer2+0xc8/0x210 [i915]
Jul 18 10:11:23 sepiroth kernel: [31932.238277] [<ffffffffa00f335a>] drm_ioctl+0x34a/0x4c0 [drm]
Jul 18 10:11:23 sepiroth kernel: [31932.238284] [<ffffffff811e6de9>] ? ext4_file_write+0x39/0xb0
Jul 18 10:11:23 sepiroth kernel: [31932.238295] [<ffffffffa025d470>] ? i915_gem_execbuffer2+0x0/0x210 [i915]
Jul 18 10:11:23 sepiroth kernel: [31932.238300] [<ffffffff8116159d>] vfs_ioctl+0x3d/0xd0
Jul 18 10:11:23 sepiroth kernel: [31932.238303] [<ffffffff81161e71>] do_vfs_ioctl+0x81/0x340
Jul 18 10:11:23 sepiroth kernel: [31932.238307] [<ffffffff81151642>] ? vfs_write+0x132/0x1a0
Jul 18 10:11:23 sepiroth kernel: [31932.238312] [<ffffffff8125df9a>] ? security_capable+0x2a/0x30
Jul 18 10:11:23 sepiroth kernel: [31932.238316] [<ffffffff8106b2a3>] ? capable+0x13/0x50
Jul 18 10:11:23 sepiroth kernel: [31932.238320] [<ffffffff811621b1>] sys_ioctl+0x81/0xa0
Jul 18 10:11:23 sepiroth kernel: [31932.238324] [<ffffffff8100a0f2>] system_call_fastpath+0x16/0x1b
Jul 18 10:11:23 sepiroth kernel: [31932.238327] Code: 44 89 f0 ba 02 00 00 00 48 89 de 83 c8 02 4c 89 ef 41 83 e4 10 44 0f 45 f0 e8 17 f3 ff ff 8b 43 4c 48 8b 53 30 48 89 de 4c 89 ef <44> 89 34 02 8b 53 4c 48 8b 43 20 83 6b 50 04 83 c2 04 83 e8 01
Jul 18 10:11:23 sepiroth kernel: [31932.238365] RIP [<ffffffffa0276516>] render_ring_flush+0xa6/0x160 [i915]
Jul 18 10:11:23 sepiroth kernel: [31932.238377] RSP <ffff88007819fbe8>
Jul 18 10:11:23 sepiroth kernel: [31932.238379] CR2: 0000000000000000
Jul 18 10:11:23 sepiroth kernel: [31932.238383] ---[ end trace baf9c993a0b079cb ]---
---8<---

Which seems to indicate to me a problem with the intel driver (again).