Crash in intel_uncore.c:619

The i915 driver crashed on Kubuntu 16.04 beta 2 on a Lenovo Thinkpad X1 3rd generation.

I think the crash happened when KDE attempted to perform automatic login. After the crash, I believe X was restarted. The login screen was shown and I could log in and use the computer normally.

[ 52.782406] ------------[ cut here ]------------
[ 52.782494] WARNING: CPU: 1 PID: 1009 at /build/linux-XwpX40/linux-4.4.0/drivers/gpu/drm/i915/intel_uncore.c:619 hsw_unclaimed_reg_debug+0x69/0x90 [i915]()
[ 52.782501] Unclaimed register detected after reading register 0x223a0
[ 52.782503] Modules linked in: ctr ccm hid_logitech_hidpp hid_generic hid_microsoft hid_logitech_dj cdc_ether usbnet r8152 snd_usb_audio mii snd_usbmidi_lib usbhid hid uvcvideo videobuf2_vmalloc videobuf2_memops videobuf2_v4l2 videobuf2_core v4l2_common videodev media binfmt_misc arc4 intel_rapl x86_pkg_temp_thermal intel_powerclamp coretemp kvm iwlmvm irqbypass mac80211 input_leds joydev serio_raw snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic iwlwifi thinkpad_acpi snd_seq_midi nvram snd_seq_midi_event cfg80211 snd_hda_intel snd_hda_codec intel_pch_thermal lpc_ich snd_hda_core snd_rawmidi snd_hwdep mei_me snd_pcm snd_seq mei shpchp snd_seq_device snd_timer snd soundcore mac_hid parport_pc ppdev lp parport autofs4 drbg ansi_cprng algif_skcipher af_alg dm_crypt crct10dif_pclmul crc32_pclmul
[ 52.782597] aesni_intel i915 aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd i2c_algo_bit drm_kms_helper psmouse e1000e syscopyarea sysfillrect ahci sysimgblt fb_sys_fops ptp libahci pps_core drm wmi video fjes
[ 52.782629] CPU: 1 PID: 1009 Comm: Xorg Tainted: G W 4.4.0-18-generic #34-Ubuntu
[ 52.782632] Hardware name: LENOVO 20BTS2YF00/20BTS2YF00, BIOS N14ET32W (1.10 ) 08/13/2015
[ 52.782635] 0000000000000086 00000000980a8dd8 ffff88024dc43cd8 ffffffff813e9243
[ 52.782640] ffff88024dc43d20 ffffffffc02b91c0 ffff88024dc43d10 ffffffff81080f62
[ 52.782643] ffff88023e980000 00000000000223a0 0000000000000102 00000000000223a0
[ 52.782647] Call Trace:
[ 52.782650] <IRQ> [<ffffffff813e9243>] dump_stack+0x63/0x90
[ 52.782673] [<ffffffff81080f62>] warn_slowpath_common+0x82/0xc0
[ 52.782678] [<ffffffff81080ffc>] warn_slowpath_fmt+0x5c/0x80
[ 52.782739] [<ffffffffc0231379>] hsw_unclaimed_reg_debug+0x69/0x90 [i915]
[ 52.782790] [<ffffffffc0234001>] gen6_read32+0xd1/0x1a0 [i915]
[ 52.782839] [<ffffffffc02274d8>] intel_lrc_irq_handler+0x38/0x240 [i915]
[ 52.782895] [<ffffffffc0053d6a>] ? drm_handle_vblank+0x1ea/0x2b0 [drm]
[ 52.782946] [<ffffffffc01e3dc7>] gen8_gt_irq_handler+0x217/0x240 [i915]
[ 52.782987] [<ffffffffc01e3e91>] gen8_irq_handler+0xa1/0x740 [i915]
[ 52.782997] [<ffffffff810da8ed>] handle_irq_event_percpu+0x8d/0x1d0
[ 52.783002] [<ffffffff810daa6e>] handle_irq_event+0x3e/0x60
[ 52.783007] [<ffffffff810ddfad>] handle_edge_irq+0x7d/0x150
[ 52.783014] [<ffffffff8103115a>] handle_irq+0x1a/0x30
[ 52.783021] [<ffffffff81826d9b>] do_IRQ+0x4b/0xd0
[ 52.783030] [<ffffffff81824e82>] common_interrupt+0x82/0x82
[ 52.783032] <EOI> [<ffffffffc0227fc4>] ? gen8_emit_request+0x224/0x320 [i915]
[ 52.783116] [<ffffffffc02155a7>] __i915_add_request+0x147/0x210 [i915]
[ 52.783157] [<ffffffffc0209b76>] i915_gem_execbuffer_retire_commands+0x26/0x30 [i915]
[ 52.783197] [<ffffffffc022872b>] intel_execlists_submission+0x2eb/0x410 [i915]
[ 52.783228] [<ffffffffc0209500>] i915_gem_do_execbuffer.isra.25+0xfa0/0x12a0 [i915]
[ 52.783262] [<ffffffffc0213651>] ? i915_gem_object_retire__write+0x51/0x90 [i915]
[ 52.783295] [<ffffffffc020a482>] i915_gem_execbuffer2+0xb2/0x240 [i915]
[ 52.783322] [<ffffffffc0217022>] ? i915_gem_busy_ioctl+0x92/0xe0 [i915]
[ 52.783369] [<ffffffffc0051712>] drm_ioctl+0x152/0x540 [drm]
[ 52.783403] [<ffffffffc020a3d0>] ? i915_gem_execbuffer+0x310/0x310 [i915]
[ 52.783412] [<ffffffff8121ff9f>] do_vfs_ioctl+0x29f/0x490
[ 52.783415] [<ffffffff81220209>] SyS_ioctl+0x79/0x90
[ 52.783423] [<ffffffff818243b2>] entry_SYSCALL_64_fastpath+0x16/0x71
[ 52.783427] ---[ end trace 8b23540298125f35 ]---

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: xorg 1:7.7+13ubuntu3
ProcVersionSignature: Ubuntu 4.4.0-18.34-generic 4.4.6
Uname: Linux 4.4.0-18-generic x86_64
ApportVersion: 2.20.1-0ubuntu1
Architecture: amd64
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: None
CurrentDesktop: KDE
Date: Wed Apr 13 13:45:12 2016
DistUpgraded: 2016-04-13 13:29:17,470 DEBUG new topwidget None
DistroCodename: xenial
DistroVariant: kubuntu
ExtraDebuggingInterest: I just need to know a workaround
GraphicsCard:
 Intel Corporation Broadwell-U Integrated Graphics [8086:1616] (rev 09) (prog-if 00 [VGA controller])
   Subsystem: Lenovo Broadwell-U Integrated Graphics [17aa:2227]
InstallationDate: Installed on 2015-08-20 (236 days ago)
InstallationMedia: Kubuntu 15.10 "Wily Werewolf" - Alpha amd64 (20150820)
JournalErrors:
 Error: command ['journalctl', '-b', '--priority=warning', '--lines=1000'] failed with exit code 1: Hint: You are currently not seeing messages from other users and the system.
       Users in the 'systemd-journal' group can see all messages. Pass -q to
       turn off this notice.
 No journal files were opened due to insufficient permissions.
MachineType: LENOVO 20BTS2YF00
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.4.0-18-generic root=/dev/mapper/kubuntu--vg-root ro quiet splash vt.handoff=7
SourcePackage: xorg
UpgradeStatus: Upgraded to xenial on 2016-04-13 (0 days ago)
dmi.bios.date: 08/13/2015
dmi.bios.vendor: LENOVO
dmi.bios.version: N14ET32W (1.10 )
dmi.board.asset.tag: Not Available
dmi.board.name: 20BTS2YF00
dmi.board.vendor: LENOVO
dmi.board.version: 0B98417 WIN
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: None
dmi.modalias: dmi:bvnLENOVO:bvrN14ET32W(1.10):bd08/13/2015:svnLENOVO:pn20BTS2YF00:pvrThinkPadX1Carbon3rd:rvnLENOVO:rn20BTS2YF00:rvr0B98417WIN:cvnLENOVO:ct10:cvrNone:
dmi.product.name: 20BTS2YF00
dmi.product.version: ThinkPad X1 Carbon 3rd
dmi.sys.vendor: LENOVO
version.compiz: compiz N/A
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.67-1
version.libgl1-mesa-dri: libgl1-mesa-dri 11.2.0-1ubuntu1
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 11.2.0-1ubuntu1
version.xserver-xorg-core: xserver-xorg-core 2:1.18.3-1ubuntu2
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.10.1-1ubuntu2
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.7.0-1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20160325-1ubuntu1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.12-1build2
xserver.bootTime: Wed Apr 13 13:34:51 2016
xserver.configfile: default
xserver.errors:

xserver.logfile: /var/log/Xorg.0.log
xserver.outputs:
 product id 1049
 vendor LGD
xserver.version: 2:1.18.3-1ubuntu2