Comment 4 for bug 1652644

I was tailing /var/log/kern.log when I switch to a new user, and then back to mine user again - then the screen goes blank. Here is the tail:

Dec 26 17:35:25 nuc gnome-session-binary[3980]: Entering running state
Dec 26 17:36:36 nuc kernel: [ 2890.006683] ------------[ cut here ]------------
Dec 26 17:36:36 nuc kernel: [ 2890.006725] WARNING: CPU: 1 PID: 1037 at /build/linux-7x12eW/linux-4.4.0/drivers/gpu/drm/drm_irq.c:1326 drm_wait_one_vblank+0x1b5/0x1c0 [drm]()
Dec 26 17:36:36 nuc kernel: [ 2890.006728] vblank wait timed out on crtc 0
Dec 26 17:36:36 nuc kernel: [ 2890.006730] Modules linked in: cfg80211 snd_hda_codec_hdmi snd_hda_intel snd_hda_codec snd_hda_core snd_hwdep intel_rapl snd_pcm x86_pkg_temp_thermal intel_powerclamp corete
mp kvm_intel snd_seq_midi snd_seq_midi_event kvm snd_rawmidi irqbypass crct10dif_pclmul crc32_pclmul ghash_clmulni_intel cryptd snd_seq joydev snd_seq_device input_leds snd_timer snd mei_me lpc_ich mei so
undcore mac_hid binfmt_misc parport_pc ppdev lp parport autofs4 hid_logitech_hidpp hid_logitech_dj usbhid hid i915 e1000e i2c_algo_bit drm_kms_helper ahci syscopyarea libahci sysfillrect sysimgblt fb_sys_
fops drm ptp pps_core video fjes
Dec 26 17:36:36 nuc kernel: [ 2890.006795] CPU: 1 PID: 1037 Comm: Xorg Not tainted 4.4.0-57-generic #78-Ubuntu
Dec 26 17:36:36 nuc kernel: [ 2890.006798] Hardware name: /DCP847SKE, BIOS GKPPT10H.86A.0060.2016.1021.1324 10/21/2016
Dec 26 17:36:36 nuc kernel: [ 2890.006801] 0000000000000286 000000003f24334e ffff8802117abb08 ffffffff813f6f33
Dec 26 17:36:36 nuc kernel: [ 2890.006806] ffff8802117abb50 ffffffffc0067b38 ffff8802117abb40 ffffffff810812d2
Dec 26 17:36:36 nuc kernel: [ 2890.006811] ffff880035667800 0000000000000000 0000000000000000 000000000002a4a0
Dec 26 17:36:36 nuc kernel: [ 2890.006816] Call Trace:
Dec 26 17:36:36 nuc kernel: [ 2890.006825] [<ffffffff813f6f33>] dump_stack+0x63/0x90
Dec 26 17:36:36 nuc kernel: [ 2890.006831] [<ffffffff810812d2>] warn_slowpath_common+0x82/0xc0
Dec 26 17:36:36 nuc kernel: [ 2890.006836] [<ffffffff8108136c>] warn_slowpath_fmt+0x5c/0x80
Dec 26 17:36:36 nuc kernel: [ 2890.006842] [<ffffffff810c3da5>] ? finish_wait+0x55/0x70
Dec 26 17:36:36 nuc kernel: [ 2890.006864] [<ffffffffc00372e5>] drm_wait_one_vblank+0x1b5/0x1c0 [drm]
Dec 26 17:36:36 nuc kernel: [ 2890.006870] [<ffffffff810c4240>] ? wake_atomic_t_function+0x60/0x60
Dec 26 17:36:36 nuc kernel: [ 2890.006923] [<ffffffffc01dbe1a>] intel_atomic_commit+0x43a/0x6f0 [i915]
Dec 26 17:36:36 nuc kernel: [ 2890.006953] [<ffffffffc005000f>] ? drm_atomic_set_crtc_for_connector+0x6f/0xe0 [drm]
Dec 26 17:36:36 nuc kernel: [ 2890.006981] [<ffffffffc0051017>] drm_atomic_commit+0x37/0x60 [drm]
Dec 26 17:36:36 nuc kernel: [ 2890.006998] [<ffffffffc00e6dc6>] drm_atomic_helper_set_config+0x76/0xb0 [drm_kms_helper]
Dec 26 17:36:36 nuc kernel: [ 2890.007024] [<ffffffffc003fe42>] drm_mode_set_config_internal+0x62/0x100 [drm]
Dec 26 17:36:36 nuc kernel: [ 2890.007050] [<ffffffffc004449c>] drm_mode_setcrtc+0x3cc/0x4f0 [drm]
Dec 26 17:36:36 nuc kernel: [ 2890.007071] [<ffffffffc0035752>] drm_ioctl+0x152/0x540 [drm]
Dec 26 17:36:36 nuc kernel: [ 2890.007096] [<ffffffffc00440d0>] ? drm_mode_setplane+0x1b0/0x1b0 [drm]
Dec 26 17:36:36 nuc kernel: [ 2890.007102] [<ffffffff8122224f>] do_vfs_ioctl+0x29f/0x490
Dec 26 17:36:36 nuc kernel: [ 2890.007106] [<ffffffff81210df1>] ? __sb_end_write+0x21/0x30
Dec 26 17:36:36 nuc kernel: [ 2890.007112] [<ffffffff8120e9fd>] ? vfs_write+0x15d/0x1a0
Dec 26 17:36:36 nuc kernel: [ 2890.007116] [<ffffffff812224b9>] SyS_ioctl+0x79/0x90
Dec 26 17:36:36 nuc kernel: [ 2890.007122] [<ffffffff818374f2>] entry_SYSCALL_64_fastpath+0x16/0x71
Dec 26 17:36:36 nuc kernel: [ 2890.007126] ---[ end trace a947275226443206 ]---
Dec 26 17:36:48 nuc kernel: [ 2902.392357] sysrq: SysRq : Emergency Sync
Dec 26 17:36:48 nuc kernel: [ 2902.403506] Emergency Sync complete
Dec 26 17:36:49 nuc kernel: [ 2903.028358] sysrq: SysRq : Emergency Remount R/O

The tail starts with the user switch to a new user, and ends with me pressing ALT+SysRq+(S+U+B), to reboot the system.