I am using lightdm as the login manager + light-locker for session locking. Since one of the recent upgrades of my archlinux x86_64 system I am constantly ending up in a black screen when trying to unlock the session (> 50% of the cases) with the kernel being tainted. I am experiencing this on two separate laptops. One is an old Thinkpad x200s and the other is a macbook pro retina. Both have an intel graphics adapter. So maybe this is a relevant commonality. Below are some dumps from the x200s system. [ 252.132051] ------------[ cut here ]------------ [ 252.132081] WARNING: CPU: 1 PID: 506 at include/linux/kref.h:46 drm_framebuffer_reference+0x64/0x70 [drm]() [ 252.132169] Modules linked in: tun ctr ccm fuse uvcvideo videobuf2_vmalloc videobuf2_memops videobuf2_v4l2 videobuf2_core v4l2_common mousedev videodev media cdc_ether usbnet iTCO_wdt mii iTCO_vendor_support cdc_wdm cdc_acm btusb btrtl btbcm coretemp btintel bluetooth kvm_intel snd_hda_codec_conexant snd_hda_codec_generic arc4 iwldvm mac80211 kvm i915 evdev snd_hda_intel irqbypass input_leds psmouse snd_hda_codec mac_hid drm_kms_helper snd_hda_core serio_raw i2c_i801 lpc_ich snd_hwdep drm snd_pcm thinkpad_acpi iwlwifi e1000e ptp pps_core wmi cfg80211 nvram snd_timer shpchp snd syscopyarea thermal soundcore sysfillrect led_class sysimgblt battery mei_me mei ac fjes rfkill acpi_cpufreq fb_sys_fops intel_agp video i2c_algo_bit intel_gtt tpm_tis button tpm processor sch_fq_codel ip_tables x_tables ext4 [ 252.132201] crc16 mbcache jbd2 jitterentropy_rng sha256_ssse3 sha256_generic hmac drbg ansi_cprng xts gf128mul algif_skcipher af_alg dm_crypt dm_mod sd_mod atkbd libps2 ahci libahci ehci_pci uhci_hcd ehci_hcd ata_generic pata_acpi usbcore usb_common libata scsi_mod i8042 serio [ 252.132206] CPU: 1 PID: 506 Comm: Xorg Not tainted 4.4.1-2-ARCH #1 [ 252.132208] Hardware name: LENOVO 74663RG/74663RG, BIOS 6DET44WW (2.08 ) 04/22/2009 [ 252.132215] 0000000000000000 0000000023d39c57 ffff8800b5f3b920 ffffffff812c7f39 [ 252.132219] 0000000000000000 ffff8800b5f3b958 ffffffff810765b2 ffff8800b5b76e40 [ 252.132223] ffff8800b560dcc0 ffff8800b560dcc0 ffff8800b6b6cc00 ffff880036fbd000 [ 252.132225] Call Trace: [ 252.132236] [<ffffffff812c7f39>] dump_stack+0x4b/0x72 [ 252.132243] [<ffffffff810765b2>] warn_slowpath_common+0x82/0xc0 [ 252.132248] [<ffffffff810766fa>] warn_slowpath_null+0x1a/0x20 [ 252.132265] [<ffffffffa044ce34>] drm_framebuffer_reference+0x64/0x70 [drm] [ 252.132278] [<ffffffffa045e88d>] drm_atomic_set_fb_for_plane+0x2d/0x90 [drm] [ 252.132290] [<ffffffffa04a8c5e>] __drm_atomic_helper_set_config+0xde/0x3c0 [drm_kms_helper] [ 252.132298] [<ffffffffa04a9ca1>] restore_fbdev_mode+0x221/0x260 [drm_kms_helper] [ 252.132305] [<ffffffffa04ac013>] drm_fb_helper_restore_fbdev_mode_unlocked+0x33/0x80 [drm_kms_helper] [ 252.132312] [<ffffffffa04ac08d>] drm_fb_helper_set_par+0x2d/0x50 [drm_kms_helper] [ 252.132351] [<ffffffffa059241a>] intel_fbdev_set_par+0x1a/0x60 [i915] [ 252.132358] [<ffffffff8133c49f>] ? fb_set_var+0x2ef/0x460 [ 252.132361] [<ffffffff8133c3e6>] fb_set_var+0x236/0x460 [ 252.132367] [<ffffffff810aa3ca>] ? check_preempt_wakeup+0xfa/0x210 [ 252.132371] [<ffffffff810a9ebd>] ? update_curr+0x7d/0x160 [ 252.132379] [<ffffffff8133308f>] fbcon_blank+0x30f/0x350 [ 252.132384] [<ffffffff8109e6a9>] ? ttwu_do_wakeup+0x19/0xe0 [ 252.132392] [<ffffffff813af743>] do_unblank_screen+0xc3/0x190 [ 252.132399] [<ffffffff813a56d9>] complete_change_console+0x59/0xe0 [ 252.132403] [<ffffffff813a5e70>] vt_ioctl+0x710/0x12e0 [ 252.132419] [<ffffffffa0447bf8>] ? drm_dropmaster_ioctl+0x68/0x80 [drm] [ 252.132432] [<ffffffffa04437e9>] ? drm_ioctl+0x189/0x540 [drm] [ 252.132436] [<ffffffff8139a061>] tty_ioctl+0x361/0xc20 [ 252.132443] [<ffffffff811de78c>] ? __vfs_write+0xcc/0x100 [ 252.132448] [<ffffffff811f0b68>] do_vfs_ioctl+0x298/0x480 [ 252.132453] [<ffffffff811fabe7>] ? __fget+0x77/0xb0 [ 252.132457] [<ffffffff811f0dc9>] SyS_ioctl+0x79/0x90 [ 252.132463] [<ffffffff81591b2e>] entry_SYSCALL_64_fastpath+0x12/0x71 [ 252.132467] ---[ end trace 06aa9f4342873b1e ]--- [ 252.132503] BUG: unable to handle kernel NULL pointer dereference at 0000000000000060 [ 252.132536] IP: [<ffffffffa058891c>] intel_fb_obj_invalidate+0x1c/0xf0 [i915] [ 252.132541] PGD b7858067 PUD 36d0d067 PMD 0 [ 252.132545] Oops: 0000 [#1] PREEMPT SMP [ 252.132612] Modules linked in: tun ctr ccm fuse uvcvideo videobuf2_vmalloc videobuf2_memops videobuf2_v4l2 videobuf2_core v4l2_common mousedev videodev media cdc_ether usbnet iTCO_wdt mii iTCO_vendor_support cdc_wdm cdc_acm btusb btrtl btbcm coretemp btintel bluetooth kvm_intel snd_hda_codec_conexant snd_hda_codec_generic arc4 iwldvm mac80211 kvm i915 evdev snd_hda_intel irqbypass input_leds psmouse snd_hda_codec mac_hid drm_kms_helper snd_hda_core serio_raw i2c_i801 lpc_ich snd_hwdep drm snd_pcm thinkpad_acpi iwlwifi e1000e ptp pps_core wmi cfg80211 nvram snd_timer shpchp snd syscopyarea thermal soundcore sysfillrect led_class sysimgblt battery mei_me mei ac fjes rfkill acpi_cpufreq fb_sys_fops intel_agp video i2c_algo_bit intel_gtt tpm_tis button tpm processor sch_fq_codel ip_tables x_tables ext4 [ 252.132635] crc16 mbcache jbd2 jitterentropy_rng sha256_ssse3 sha256_generic hmac drbg ansi_cprng xts gf128mul algif_skcipher af_alg dm_crypt dm_mod sd_mod atkbd libps2 ahci libahci ehci_pci uhci_hcd ehci_hcd ata_generic pata_acpi usbcore usb_common libata scsi_mod i8042 serio [ 252.132639] CPU: 1 PID: 506 Comm: Xorg Tainted: G W 4.4.1-2-ARCH #1 [ 252.132641] Hardware name: LENOVO 74663RG/74663RG, BIOS 6DET44WW (2.08 ) 04/22/2009 [ 252.132644] task: ffff880036802640 ti: ffff8800b5f38000 task.ti: ffff8800b5f38000 [ 252.132678] RIP: 0010:[<ffffffffa058891c>] [<ffffffffa058891c>] intel_fb_obj_invalidate+0x1c/0xf0 [i915] [ 252.132681] RSP: 0018:ffff8800b5f3ba58 EFLAGS: 00010246 [ 252.132683] RAX: ffff880036802640 RBX: ffff8800b5dc8800 RCX: 0000000001d89a01 [ 252.132685] RDX: ffff8800b5b76e40 RSI: 0000000000000000 RDI: ffff8800b5dc8800 [ 252.132687] RBP: ffff8800b5f3ba80 R08: 0000000000018ac0 R09: ffffffffa045ccf6 [ 252.132689] R10: ffffea0004d9d240 R11: ffff880135ac6540 R12: 0000000000000000 [ 252.132691] R13: 0000000000000000 R14: 0000000000200001 R15: 0000000000000080 [ 252.132694] FS: 00007f18ad8e2940(0000) GS:ffff88013bc80000(0000) knlGS:0000000000000000 [ 252.132697] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b [ 252.132699] CR2: 0000000000000060 CR3: 0000000135d8a000 CR4: 00000000000406e0 [ 252.132701] Stack: [ 252.132706] ffff880136134900 ffff8800b65ad000 0000000000000000 0000000000200001 [ 252.132710] 0000000000000080 ffff8800b5f3baa0 ffffffffa0592443 000000008133c49f [ 252.132714] ffff8800b5f3bc48 ffff8800b5f3bc18 ffffffff8133c3e6 ffff8800b65ad060 [ 252.132715] Call Trace: [ 252.132746] [<ffffffffa0592443>] intel_fbdev_set_par+0x43/0x60 [i915] [ 252.132750] [<ffffffff8133c3e6>] fb_set_var+0x236/0x460 [ 252.132756] [<ffffffff810aa3ca>] ? check_preempt_wakeup+0xfa/0x210 [ 252.132759] [<ffffffff810a9ebd>] ? update_curr+0x7d/0x160 [ 252.132766] [<ffffffff8133308f>] fbcon_blank+0x30f/0x350 [ 252.132770] [<ffffffff8109e6a9>] ? ttwu_do_wakeup+0x19/0xe0 [ 252.132776] [<ffffffff813af743>] do_unblank_screen+0xc3/0x190 [ 252.132781] [<ffffffff813a56d9>] complete_change_console+0x59/0xe0 [ 252.132786] [<ffffffff813a5e70>] vt_ioctl+0x710/0x12e0 [ 252.132802] [<ffffffffa0447bf8>] ? drm_dropmaster_ioctl+0x68/0x80 [drm] [ 252.132815] [<ffffffffa04437e9>] ? drm_ioctl+0x189/0x540 [drm] [ 252.132818] [<ffffffff8139a061>] tty_ioctl+0x361/0xc20 [ 252.132824] [<ffffffff811de78c>] ? __vfs_write+0xcc/0x100 [ 252.132828] [<ffffffff811f0b68>] do_vfs_ioctl+0x298/0x480 [ 252.132832] [<ffffffff811fabe7>] ? __fget+0x77/0xb0 [ 252.132836] [<ffffffff811f0dc9>] SyS_ioctl+0x79/0x90 [ 252.132840] [<ffffffff81591b2e>] entry_SYSCALL_64_fastpath+0x12/0x71 [ 252.132883] Code: 41 5f 5d c3 90 66 2e 0f 1f 84 00 00 00 00 00 66 66 66 66 90 55 48 89 e5 41 57 41 56 41 55 41 54 41 89 f5 53 4c 8b 67 08 48 89 fb <41> 8b 44 24 60 4d 8b 74 24 28 83 f8 01 74 58 8b b3 5c 01 00 00 [ 252.132916] RIP [<ffffffffa058891c>] intel_fb_obj_invalidate+0x1c/0xf0 [i915] [ 252.132917] RSP <ffff8800b5f3ba58> [ 252.132918] CR2: 0000000000000060 [ 252.132921] ---[ end trace 06aa9f4342873b1f ]--- languitar@milt ~ $ uname -a Linux milt 4.4.1-2-ARCH #1 SMP PREEMPT Wed Feb 3 13:12:33 UTC 2016 x86_64 GNU/Linux languitar@milt ~ $ lspci 00:00.0 Host bridge: Intel Corporation Mobile 4 Series Chipset Memory Controller Hub (rev 07) 00:02.0 VGA compatible controller: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 07) 00:02.1 Display controller: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 07) 00:03.0 Communication controller: Intel Corporation Mobile 4 Series Chipset MEI Controller (rev 07) 00:03.2 IDE interface: Intel Corporation Mobile 4 Series Chipset PT IDER Controller (rev 07) 00:03.3 Serial controller: Intel Corporation Mobile 4 Series Chipset AMT SOL Redirection (rev 07) 00:19.0 Ethernet controller: Intel Corporation 82567LM Gigabit Network Connection (rev 03) 00:1a.0 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #4 (rev 03) 00:1a.1 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #5 (rev 03) 00:1a.2 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #6 (rev 03) 00:1a.7 USB controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #2 (rev 03) 00:1b.0 Audio device: Intel Corporation 82801I (ICH9 Family) HD Audio Controller (rev 03) 00:1c.0 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 1 (rev 03) 00:1c.1 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 2 (rev 03) 00:1c.2 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 3 (rev 03) 00:1c.3 PCI bridge: Intel Corporation 82801I (ICH9 Family) PCI Express Port 4 (rev 03) 00:1d.0 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #1 (rev 03) 00:1d.1 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #2 (rev 03) 00:1d.2 USB controller: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #3 (rev 03) 00:1d.7 USB controller: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #1 (rev 03) 00:1e.0 PCI bridge: Intel Corporation 82801 Mobile PCI Bridge (rev 93) 00:1f.0 ISA bridge: Intel Corporation ICH9M-E LPC Interface Controller (rev 03) 00:1f.2 SATA controller: Intel Corporation 82801IBM/IEM (ICH9M/ICH9M-E) 4 port SATA Controller [AHCI mode] (rev 03) 00:1f.3 SMBus: Intel Corporation 82801I (ICH9 Family) SMBus Controller (rev 03) 03:00.0 Network controller: Intel Corporation Ultimate N WiFi Link 5300 04:00.0 Memory controller: Intel Corporation Turbo Memory Controller (rev 11) 00:02.0 VGA compatible controller: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 07) (prog-if 00 [VGA controller]) Subsystem: Lenovo Device 20e4 Flags: bus master, fast devsel, latency 0, IRQ 33 Memory at f2000000 (64-bit, non-prefetchable) [size=4M] Memory at d0000000 (64-bit, prefetchable) [size=256M] I/O ports at 1800 [size=8] Expansion ROM at <unassigned> [disabled] Capabilities: <access denied> Kernel driver in use: i915 Kernel modules: i915 languitar@milt ~ $ lsmod Module Size Used by tun 28672 2 ctr 16384 2 ccm 20480 2 fuse 90112 3 uvcvideo 86016 0 videobuf2_vmalloc 16384 1 uvcvideo videobuf2_memops 16384 1 videobuf2_vmalloc videobuf2_v4l2 24576 1 uvcvideo videobuf2_core 32768 2 uvcvideo,videobuf2_v4l2 v4l2_common 16384 1 videobuf2_v4l2 mousedev 20480 0 videodev 147456 4 uvcvideo,v4l2_common,videobuf2_core,videobuf2_v4l2 media 20480 2 uvcvideo,videodev cdc_ether 16384 0 usbnet 36864 1 cdc_ether iTCO_wdt 16384 0 mii 16384 1 usbnet iTCO_vendor_support 16384 1 iTCO_wdt cdc_wdm 20480 0 cdc_acm 32768 0 btusb 40960 0 btrtl 16384 1 btusb btbcm 16384 1 btusb coretemp 16384 0 btintel 16384 1 btusb bluetooth 450560 4 btbcm,btrtl,btusb,btintel kvm_intel 167936 0 snd_hda_codec_conexant 24576 1 snd_hda_codec_generic 65536 1 snd_hda_codec_conexant arc4 16384 2 iwldvm 180224 0 mac80211 643072 1 iwldvm kvm 462848 1 kvm_intel i915 1134592 4 evdev 24576 5 snd_hda_intel 32768 1 irqbypass 16384 1 kvm input_leds 16384 0 psmouse 118784 0 snd_hda_codec 106496 3 snd_hda_codec_conexant,snd_hda_codec_generic,snd_hda_intel mac_hid 16384 0 drm_kms_helper 106496 1 i915 snd_hda_core 49152 4 snd_hda_codec_conexant,snd_hda_codec_generic,snd_hda_codec,snd_hda_intel serio_raw 16384 0 i2c_i801 20480 0 lpc_ich 24576 0 snd_hwdep 16384 1 snd_hda_codec drm 286720 6 i915,drm_kms_helper snd_pcm 86016 3 snd_hda_codec,snd_hda_intel,snd_hda_core thinkpad_acpi 73728 0 iwlwifi 163840 1 iwldvm e1000e 217088 0 ptp 20480 1 e1000e pps_core 20480 1 ptp wmi 20480 0 cfg80211 475136 3 iwlwifi,mac80211,iwldvm nvram 16384 1 thinkpad_acpi snd_timer 28672 1 snd_pcm shpchp 32768 0 snd 65536 10 snd_hwdep,snd_timer,snd_hda_codec_conexant,snd_pcm,snd_hda_codec_generic,snd_hda_codec,snd_hda_intel,thinkpad_acpi syscopyarea 16384 1 drm_kms_helper thermal 20480 0 soundcore 16384 1 snd sysfillrect 16384 1 drm_kms_helper led_class 16384 3 iwldvm,thinkpad_acpi,input_leds sysimgblt 16384 1 drm_kms_helper battery 20480 0 mei_me 32768 0 mei 81920 1 mei_me ac 16384 0 fjes 28672 0 rfkill 20480 5 cfg80211,thinkpad_acpi,bluetooth acpi_cpufreq 20480 1 fb_sys_fops 16384 1 drm_kms_helper intel_agp 20480 0 video 36864 2 i915,thinkpad_acpi i2c_algo_bit 16384 1 i915 intel_gtt 20480 3 i915,intel_agp tpm_tis 20480 0 button 16384 1 i915 tpm 36864 1 tpm_tis processor 32768 3 acpi_cpufreq sch_fq_codel 20480 6 ip_tables 28672 0 x_tables 28672 1 ip_tables ext4 512000 3 crc16 16384 2 ext4,bluetooth mbcache 20480 1 ext4 jbd2 90112 1 ext4 jitterentropy_rng 16384 0 sha256_ssse3 32768 1 sha256_generic 24576 1 sha256_ssse3 hmac 16384 1 drbg 32768 1 ansi_cprng 16384 0 xts 16384 1 gf128mul 16384 1 xts algif_skcipher 20480 0 af_alg 16384 1 algif_skcipher dm_crypt 28672 1 dm_mod 102400 12 dm_crypt sd_mod 36864 3 atkbd 24576 0 libps2 16384 2 atkbd,psmouse ahci 36864 2 libahci 28672 1 ahci ehci_pci 16384 0 uhci_hcd 45056 0 ehci_hcd 69632 1 ehci_pci ata_generic 16384 0 pata_acpi 16384 0 usbcore 196608 9 btusb,uhci_hcd,uvcvideo,ehci_hcd,ehci_pci,usbnet,cdc_acm,cdc_wdm,cdc_ether usb_common 16384 1 usbcore libata 196608 4 ahci,pata_acpi,libahci,ata_generic scsi_mod 151552 2 libata,sd_mod i8042 24576 1 libps2 serio 20480 6 serio_raw,atkbd,i8042,psmouse
I have exactly the same problem for a few months now. I'm also using LightDM with LightLocker on Antergos linux. One thing helped me though, setting AccelMethod to uxa, according to this Wiki article: https://wiki.archlinux.org/index.php/Intel_graphics#SNA_issues