Locking screen hangs system and causes DRM kernel msg for intel 915 module

[Chiron]

I have a pair of Thinkpad T420s laptops that hang and require reboot via cli on a vty whenever the screen locks. When I move the mouse after it locks and blanks the screen, I see the lock screen and can move the cursor, but no response from anything on the lock screen. I cannot type password and none of the icons in the top right respond to being clicked. I have to use ALT+F1 to login at a vty and reboot the machine.

Dmesg reveals a kernel module issue from i915 module that looks DRM related in some manner. I do not experience this issue on normal Ubuntu, Ubuntu Gnome, or other Ubuntu based distributions. For the below, I booted up, logged in, inserted and mounted my memstick for copying dmesg output and locked the laptop with Win+L. Then I switched to a vty and logged in at cli and copied dmesg to a text file.

Dmesg tailing output:

[ 224.873477] ------------[ cut here ]------------
[ 224.873510] WARNING: CPU: 2 PID: 2392 at /build/linux-BwgxJb/linux-4.4.0/drivers/gpu/drm/drm_irq.c:1326 drm_wait_one_vblank+0x1b5/0x1c0 [drm]()
[ 224.873511] vblank wait timed out on crtc 0
[ 224.873569] Modules linked in: uas usb_storage msr bnep drbg ansi_cprng dm_crypt btusb uvcvideo videobuf2_vmalloc videobuf2_memops videobuf2_v4l2 btrtl videobuf2_core btbcm v4l2_common btintel bluetooth videodev media arc4 iwldvm mac80211 intel_rapl x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm snd_hda_codec_hdmi irqbypass snd_hda_codec_conexant wl(POE) crct10dif_pclmul crc32_pclmul snd_hda_codec_generic snd_hda_intel iwlwifi snd_hda_codec aesni_intel thinkpad_acpi snd_hda_core aes_x86_64 snd_hwdep lrw gf128mul glue_helper nvram snd_pcm cfg80211 snd_seq_midi snd_seq_midi_event snd_rawmidi snd_seq ablk_helper snd_seq_device snd_timer mei_me cryptd mei snd input_leds joydev shpchp serio_raw soundcore lpc_ich mac_hid parport_pc ppdev lp parport autofs4 i915 i2c_algo_bit drm_kms_helper
[ 224.873580] psmouse syscopyarea sysfillrect e1000e sysimgblt ahci fb_sys_fops libahci sdhci_pci ptp sdhci pps_core drm wmi fjes video
[ 224.873583] CPU: 2 PID: 2392 Comm: Xorg Tainted: P OE 4.4.0-43-generic #63-Ubuntu
[ 224.873584] Hardware name: LENOVO 417152U/417152U, BIOS 8CET46WW (1.26 ) 07/11/2011
[ 224.873588] 0000000000000286 00000000e459d6ef ffff88009d923838 ffffffff813f1f93
[ 224.873591] ffff88009d923880 ffffffffc0067b38 ffff88009d923870 ffffffff81081212
[ 224.873593] ffff8800349ca000 0000000000000000 0000000000000000 0000000000002b5b
[ 224.873594] Call Trace:
[ 224.873602] [<ffffffff813f1f93>] dump_stack+0x63/0x90
[ 224.873608] [<ffffffff81081212>] warn_slowpath_common+0x82/0xc0
[ 224.873611] [<ffffffff810812ac>] warn_slowpath_fmt+0x5c/0x80
[ 224.873616] [<ffffffff810c3935>] ? finish_wait+0x55/0x70
[ 224.873637] [<ffffffffc00372e5>] drm_wait_one_vblank+0x1b5/0x1c0 [drm]
[ 224.873640] [<ffffffff810c3dd0>] ? wake_atomic_t_function+0x60/0x60
[ 224.873687] [<ffffffffc0231dda>] intel_atomic_commit+0x43a/0x6f0 [i915]
[ 224.873713] [<ffffffffc0050987>] ? drm_atomic_add_affected_connectors+0x27/0xf0 [drm]
[ 224.873738] [<ffffffffc0051017>] drm_atomic_commit+0x37/0x60 [drm]
[ 224.873754] [<ffffffffc0187e4f>] restore_fbdev_mode+0x22f/0x260 [drm_kms_helper]
[ 224.873779] [<ffffffffc004f79a>] ? drm_modeset_lock_all_ctx+0x9a/0xb0 [drm]
[ 224.873792] [<ffffffffc018a023>] drm_fb_helper_restore_fbdev_mode_unlocked+0x33/0x80 [drm_kms_helper]
[ 224.873802] [<ffffffffc018a09d>] drm_fb_helper_set_par+0x2d/0x50 [drm_kms_helper]
[ 224.873843] [<ffffffffc0246e1a>] intel_fbdev_set_par+0x1a/0x60 [i915]
[ 224.873849] [<ffffffff8147544f>] ? fb_set_var+0x2ef/0x460
[ 224.873852] [<ffffffff81475396>] fb_set_var+0x236/0x460
[ 224.873855] [<ffffffff810b4e59>] ? update_curr+0x79/0x160
[ 224.873860] [<ffffffff8146b68f>] fbcon_blank+0x30f/0x350
[ 224.873863] [<ffffffff8102d8c7>] ? __switch_to+0x437/0x5c0
[ 224.873868] [<ffffffff81502a53>] do_unblank_screen+0xd3/0x1a0
[ 224.873873] [<ffffffff814f7b29>] complete_change_console+0x59/0xe0
[ 224.873876] [<ffffffff814f82c0>] vt_ioctl+0x710/0x12f0
[ 224.873896] [<ffffffffc0035789>] ? drm_ioctl+0x189/0x540 [drm]
[ 224.873899] [<ffffffff814eb57f>] tty_ioctl+0x35f/0xc40
[ 224.873904] [<ffffffff811c04fd>] ? handle_mm_fault+0xcdd/0x1820
[ 224.873907] [<ffffffff8122123f>] do_vfs_ioctl+0x29f/0x490
[ 224.873910] [<ffffffff812214a9>] SyS_ioctl+0x79/0x90
[ 224.873914] [<ffffffff818318b2>] entry_SYSCALL_64_fastpath+0x16/0x71
[ 224.873916] ---[ end trace 8bbe075235b3fd1e ]---