Hello, I see that the problem is still present on Ubuntu 16.04 x86_64 on my Thinkpad T420. Can anybody confirm that? Also, what's the easiest workaround at the moment? Thanks.

holden@lynx:~$ lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 16.04.1 LTS
Release:	16.04
Codename:	xenial

holden@lynx:~$ uname -a
Linux lynx 4.4.0-38-generic #57-Ubuntu SMP Tue Sep 6 15:42:33 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

Sep 23 00:33:20 lynx kernel: [  965.988645] ------------[ cut here ]------------
Sep 23 00:33:20 lynx kernel: [  965.988696] WARNING: CPU: 2 PID: 1328 at /build/linux-R0TiM8/linux-4.4.0/drivers/gpu/drm/drm_irq.c:1326 drm_wait_one_vblank+0x1b5/0x1c0 [drm]()
Sep 23 00:33:20 lynx kernel: [  965.988698] vblank wait timed out on crtc 0
Sep 23 00:33:20 lynx kernel: [  965.988771] Modules linked in: nls_iso8859_1 drbg ansi_cprng ctr ccm bnep intel_rapl x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel arc4 snd_hda_codec_hdmi kvm snd_hda_codec_conexant irqbypass iwldvm crct10dif_pclmul crc32_pclmul snd_hda_codec_generic mac80211 snd_hda_intel snd_hda_codec uvcvideo aesni_intel videobuf2_vmalloc videobuf2_memops videobuf2_v4l2 videobuf2_core aes_x86_64 v4l2_common snd_hda_core lrw snd_hwdep gf128mul videodev glue_helper media ablk_helper thinkpad_acpi cryptd nvram snd_pcm snd_seq_midi snd_seq_midi_event snd_rawmidi iwlwifi snd_seq btusb input_leds joydev btrtl btbcm btintel snd_seq_device cfg80211 bluetooth snd_timer snd soundcore mei_me mei lpc_ich serio_raw shpchp mac_hid parport_pc ppdev lp parport autofs4 mmc_block i915 i2c_algo_bit drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops e1000e drm firewire_ohci ahci psmouse sdhci_pci ptp sdhci pps_core libahci firewire_core crc_itu_t wmi fjes video
Sep 23 00:33:20 lynx kernel: [  965.988793] CPU: 2 PID: 1328 Comm: Xorg Not tainted 4.4.0-38-generic #57-Ubuntu
Sep 23 00:33:20 lynx kernel: [  965.988795] Hardware name: LENOVO 4236BE3/4236BE3, BIOS 83ET78WW (1.48 ) 01/21/2016
Sep 23 00:33:20 lynx kernel: [  965.988802]  0000000000000286 00000000b106ac7e ffff8802137af860 ffffffff813f1b73
Sep 23 00:33:20 lynx kernel: [  965.988805]  ffff8802137af8a8 ffffffffc010ab38 ffff8802137af898 ffffffff810811c2
Sep 23 00:33:20 lynx kernel: [  965.988809]  ffff880035847000 0000000000000000 0000000000000000 000000000000e240
Sep 23 00:33:20 lynx kernel: [  965.988810] Call Trace:
Sep 23 00:33:20 lynx kernel: [  965.988824]  [<ffffffff813f1b73>] dump_stack+0x63/0x90
Sep 23 00:33:20 lynx kernel: [  965.988833]  [<ffffffff810811c2>] warn_slowpath_common+0x82/0xc0
Sep 23 00:33:20 lynx kernel: [  965.988837]  [<ffffffff8108125c>] warn_slowpath_fmt+0x5c/0x80
Sep 23 00:33:20 lynx kernel: [  965.988846]  [<ffffffff810c38e5>] ? finish_wait+0x55/0x70
Sep 23 00:33:20 lynx kernel: [  965.988877]  [<ffffffffc00da2e5>] drm_wait_one_vblank+0x1b5/0x1c0 [drm]
Sep 23 00:33:20 lynx kernel: [  965.988882]  [<ffffffff810c3d80>] ? wake_atomic_t_function+0x60/0x60
Sep 23 00:33:20 lynx kernel: [  965.988959]  [<ffffffffc0262dca>] intel_atomic_commit+0x43a/0x6f0 [i915]
Sep 23 00:33:20 lynx kernel: [  965.989001]  [<ffffffffc00f3977>] ? drm_atomic_add_affected_connectors+0x27/0xf0 [drm]
Sep 23 00:33:20 lynx kernel: [  965.989039]  [<ffffffffc00f4007>] drm_atomic_commit+0x37/0x60 [drm]
Sep 23 00:33:20 lynx kernel: [  965.989063]  [<ffffffffc01c0e1f>] restore_fbdev_mode+0x22f/0x260 [drm_kms_helper]
Sep 23 00:33:20 lynx kernel: [  965.989100]  [<ffffffffc00f278a>] ? drm_modeset_lock_all_ctx+0x9a/0xb0 [drm]
Sep 23 00:33:20 lynx kernel: [  965.989120]  [<ffffffffc01c2ff3>] drm_fb_helper_restore_fbdev_mode_unlocked+0x33/0x80 [drm_kms_helper]
Sep 23 00:33:20 lynx kernel: [  965.989136]  [<ffffffffc01c306d>] drm_fb_helper_set_par+0x2d/0x50 [drm_kms_helper]
Sep 23 00:33:20 lynx kernel: [  965.989200]  [<ffffffffc0277e0a>] intel_fbdev_set_par+0x1a/0x60 [i915]
Sep 23 00:33:20 lynx kernel: [  965.989208]  [<ffffffff81474f36>] fb_set_var+0x236/0x460
Sep 23 00:33:20 lynx kernel: [  965.989216]  [<ffffffff810b276c>] ? __enqueue_entity+0x6c/0x70
Sep 23 00:33:20 lynx kernel: [  965.989220]  [<ffffffff810b8337>] ? enqueue_entity+0x3a7/0xc70
Sep 23 00:33:20 lynx kernel: [  965.989226]  [<ffffffff810b366f>] ? select_idle_sibling+0xef/0x120
Sep 23 00:33:20 lynx kernel: [  965.989233]  [<ffffffff8146b22f>] fbcon_blank+0x30f/0x350
Sep 23 00:33:20 lynx kernel: [  965.989241]  [<ffffffff81502573>] do_unblank_screen+0xd3/0x1a0
Sep 23 00:33:20 lynx kernel: [  965.989247]  [<ffffffff814f7bda>] vt_ioctl+0x50a/0x12f0
Sep 23 00:33:20 lynx kernel: [  965.989253]  [<ffffffff81295121>] ? ext4_free_inode+0x251/0x660
Sep 23 00:33:20 lynx kernel: [  965.989260]  [<ffffffff814eb09f>] tty_ioctl+0x35f/0xc40
Sep 23 00:33:20 lynx kernel: [  965.989267]  [<ffffffff810e7ed7>] ? call_rcu_sched+0x17/0x20
Sep 23 00:33:20 lynx kernel: [  965.989275]  [<ffffffff812baa8b>] ? ext4_destroy_inode+0x3b/0xa0
Sep 23 00:33:20 lynx kernel: [  965.989283]  [<ffffffff812503dc>] ? __fsnotify_inode_delete+0x1c/0x20
Sep 23 00:33:20 lynx kernel: [  965.989291]  [<ffffffff81228db8>] ? destroy_inode+0x38/0x60
Sep 23 00:33:20 lynx kernel: [  965.989295]  [<ffffffff81228f0d>] ? evict+0x12d/0x190
Sep 23 00:33:20 lynx kernel: [  965.989299]  [<ffffffff812211ff>] do_vfs_ioctl+0x29f/0x490
Sep 23 00:33:20 lynx kernel: [  965.989305]  [<ffffffff8121db99>] ? do_unlinkat+0xe9/0x2d0
Sep 23 00:33:20 lynx kernel: [  965.989308]  [<ffffffff81221469>] SyS_ioctl+0x79/0x90
Sep 23 00:33:20 lynx kernel: [  965.989316]  [<ffffffff818306f2>] entry_SYSCALL_64_fastpath+0x16/0x71
Sep 23 00:33:20 lynx kernel: [  965.989320] ---[ end trace 2c391ba1df8f5adb ]---