I was testing Linux kernel 4.10-rc5 to see whether the hang/lock up issues with 4.9 have been gone. Meanwhile I also received mesa 17.0.0~rc1 via Debian Sid/Unstable packages. I am using the Modesetting driver with glamor. Hardware is ThinkPad T520 with Sandybridge graphics – I am back at kernel 4.8 again as I need this laptop for work, I am not willing to do a bisect for an occasionally happening issue that can lead to data loss due to having to forcefully switch of the machine:

martin@merkaba:~> phoronix-test-suite system-info
[…]
Hardware:
Processor: Intel Core i5-2520M @ 3.20GHz (4 Cores), Motherboard: LENOVO 42433WG, Chipset: Intel 2nd Generation Core Family DRAM, Memory: 16384MB, Disk: 300GB INTEL SSDSA2CW30 + 480GB Crucial_CT480M50, Graphics: Intel 2nd Generation Core Family IGP, Audio: Conexant CX20590, Monitor: P24T-7 LED, Network: Intel 82579LM Gigabit Connection + Intel Centrino Advanced-N 6205

Software:
OS: Debian 9.0, Kernel: 4.8.15-tp520-btrfstrim+ (x86_64), Desktop: KDE Frameworks 5, Display Server: X Server 1.19.1, Display Driver: modesetting 1.19.1, OpenGL: 3.3 Mesa 17.0.0-rc1, File-System: btrfs, Screen Resolution: 3840x1080


With 4.10-rc5, but not with 4.8.x I occasionally have a black screen after switching between two desktop sessions. Both are Plasma sessions, one is on TTY7, the other on TTY8.

# How to reproduce
Honestly I do not know yet. It only happens occasionally. What I did:

1. Have two Plasma sessions open.
2. Work on TTY8.
3. Switch to TTY7 by pressing Ctrl-Alt-F7 after a while.

It doesn´t happen all the time.

# Actual results
Black screen and backtrace in kernel log:

Jan 25 12:05:58 merkaba kernel: [10113.317980] ------------[ cut here ]------------
Jan 25 12:05:58 merkaba kernel: [10113.318003] WARNING: CPU: 2 PID: 3795 at drivers/gpu/drm/i915/i915_vma.c:476 __i915_vma_do_pin+0x38b/0x450
Jan 25 12:05:58 merkaba kernel: [10113.318007] WARN_ON(bound & (1UL << (5)))
Jan 25 12:05:58 merkaba kernel: [10113.318009] Modules linked in: acpi_call(O) pci_stub vboxpci(O) vboxnetadp(O) vboxnetflt(O) vboxdrv(O) xt_CHECKSUM iptable_mangle ipt_MAS
QUERADE nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp tun bridge stp llc snd_usb_a
udio snd_usbmidi_lib snd_rawmidi snd_seq_device ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter uinput binfmt_misc nls_utf8 nls_cp437 vfat fat ext4 crc16 
jbd2 fscrypto mbcache intel_rapl iosf_mbi x86_pkg_temp_thermal intel_powerclamp kvm_intel kvm irqbypass crct10dif_pclmul crc32_pclmul ghash_clmulni_intel pcbc snd_hda_codec
_hdmi snd_hda_codec_conexant snd_hda_codec_generic iwldvm mac80211 aesni_intel aes_x86_64 crypto_simd glue_helper cryptd pcspkr serio_raw iwlwifi sg cfg80211
Jan 25 12:05:58 merkaba kernel: [10113.318129]  lpc_ich mfd_core snd_hda_intel snd_hda_codec shpchp snd_hwdep snd_hda_core mei_me thinkpad_acpi mei snd_pcm snd_timer nvram 
snd soundcore rfkill battery ac tpm_tis tpm_tis_core tpm evdev joydev sbs sbshc coretemp hdaps(O) tp_smapi(O) thinkpad_ec(O) loop firewire_sbp2 ecryptfs cbc hmac encrypted_
keys sunrpc ip_tables x_tables autofs4 btrfs raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c crc32c_generic raid1 raid0 mul
tipath linear md_mod dm_mod sr_mod cdrom sd_mod hid_generic usbhid hid crc32c_intel ahci libahci psmouse libata scsi_mod i2c_i801 sdhci_pci sdhci firewire_ohci firewire_core mmc_core crc_itu_t ehci_pci ehci_hcd e1000e ptp usbcore pps_core thermal
Jan 25 12:05:58 merkaba kernel: [10113.318282] CPU: 2 PID: 3795 Comm: Xorg Tainted: G           O    4.10.0-rc5-tp520+ #78
Jan 25 12:05:58 merkaba kernel: [10113.318287] Hardware name: LENOVO 42433WG/42433WG, BIOS 8AET63WW (1.43 ) 05/08/2013
Jan 25 12:05:58 merkaba kernel: [10113.318292] Call Trace:
Jan 25 12:05:58 merkaba kernel: [10113.318307]  dump_stack+0x4d/0x63
Jan 25 12:05:58 merkaba kernel: [10113.318316]  __warn+0xcb/0xf0
Jan 25 12:05:58 merkaba kernel: [10113.318324]  warn_slowpath_fmt+0x4f/0x60
Jan 25 12:05:58 merkaba kernel: [10113.318334]  __i915_vma_do_pin+0x38b/0x450
Jan 25 12:05:58 merkaba kernel: [10113.318343]  ? ttwu_do_wakeup+0x19/0xf0
Jan 25 12:05:58 merkaba kernel: [10113.318351]  ? ttwu_do_activate+0x6f/0x80
Jan 25 12:05:58 merkaba kernel: [10113.318361]  i915_gem_execbuffer_reserve_vma.isra.31+0x144/0x1b0
Jan 25 12:05:58 merkaba kernel: [10113.318371]  i915_gem_execbuffer_reserve.isra.32+0x30a/0x3a0
Jan 25 12:05:58 merkaba kernel: [10113.318392]  i915_gem_do_execbuffer.isra.38+0x60d/0x1790
Jan 25 12:05:58 merkaba kernel: [10113.318403]  ? __wake_up_sync_key+0x50/0x60
Jan 25 12:05:58 merkaba kernel: [10113.318415]  ? sock_def_readable+0x72/0x80
Jan 25 12:05:58 merkaba kernel: [10113.318425]  i915_gem_execbuffer2+0xc5/0x240
Jan 25 12:05:58 merkaba kernel: [10113.318434]  drm_ioctl+0x20c/0x490
Jan 25 12:05:58 merkaba kernel: [10113.318442]  ? i915_gem_execbuffer+0x2e0/0x2e0
Jan 25 12:05:58 merkaba kernel: [10113.318456]  do_vfs_ioctl+0x94/0x5d0
Jan 25 12:05:58 merkaba kernel: [10113.318464]  ? __fget+0x77/0xb0
Jan 25 12:05:58 merkaba kernel: [10113.318469]  ? __fget+0x77/0xb0
Jan 25 12:05:58 merkaba kernel: [10113.318475]  SyS_ioctl+0x79/0x90
Jan 25 12:05:58 merkaba kernel: [10113.318483]  entry_SYSCALL_64_fastpath+0x13/0x94
Jan 25 12:05:58 merkaba kernel: [10113.318488] RIP: 0033:0x7f38fb08dca7
Jan 25 12:05:58 merkaba kernel: [10113.318492] RSP: 002b:00007ffe44c4e708 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
Jan 25 12:05:58 merkaba kernel: [10113.318498] RAX: ffffffffffffffda RBX: 0000562b7ff51990 RCX: 00007f38fb08dca7
Jan 25 12:05:58 merkaba kernel: [10113.318501] RDX: 00007ffe44c4e750 RSI: 0000000040406469 RDI: 0000000000000019
Jan 25 12:05:58 merkaba kernel: [10113.318505] RBP: 0000562b7f0f1060 R08: 0000000000000000 R09: 0000000000000000
Jan 25 12:05:58 merkaba kernel: [10113.318508] R10: 0000000000000000 R11: 0000000000000246 R12: 0000562b7f9c44a0
Jan 25 12:05:58 merkaba kernel: [10113.318511] R13: 0000000000000000 R14: 0000562b80017490 R15: 0000000000000000
Jan 25 12:05:58 merkaba kernel: [10113.318517] ---[ end trace 9761d36f6e68dba7 ]---
Jan 25 12:05:58 merkaba at-spi2-registr[8758]: Could not open X display
Jan 25 12:05:58 merkaba kernel: [10113.919097] ------------[ cut here ]------------
Jan 25 12:05:58 merkaba kernel: [10113.919109] WARNING: CPU: 0 PID: 8474 at drivers/gpu/drm/i915/i915_vma.c:525 i915_vma_close+0xa3/0xb0
Jan 25 12:05:58 merkaba kernel: [10113.919112] WARN_ON(i915_vma_unbind(vma))
Jan 25 12:05:58 merkaba kernel: [10113.919113] Modules linked in: acpi_call(O) pci_stub vboxpci(O) vboxnetadp(O) vboxnetflt(O) vboxdrv(O) xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp tun bridge stp llc snd_usb_audio snd_usbmidi_lib snd_rawmidi snd_seq_device ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter uinput binfmt_misc nls_utf8 nls_cp437 vfat fat ext4 crc16 jbd2 fscrypto mbcache intel_rapl iosf_mbi x86_pkg_temp_thermal intel_powerclamp kvm_intel kvm irqbypass crct10dif_pclmul crc32_pclmul ghash_clmulni_intel pcbc snd_hda_codec_hdmi snd_hda_codec_conexant snd_hda_codec_generic iwldvm mac80211 aesni_intel aes_x86_64 crypto_simd glue_helper cryptd pcspkr serio_raw iwlwifi sg cfg80211
Jan 25 12:05:58 merkaba kernel: [10113.919161]  lpc_ich mfd_core snd_hda_intel snd_hda_codec shpchp snd_hwdep snd_hda_core mei_me thinkpad_acpi mei snd_pcm snd_timer nvram snd soundcore rfkill battery ac tpm_tis tpm_tis_core tpm evdev joydev sbs sbshc coretemp hdaps(O) tp_smapi(O) thinkpad_ec(O) loop firewire_sbp2 ecryptfs cbc hmac encrypted_keys sunrpc ip_tables x_tables autofs4 btrfs raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c crc32c_generic raid1 raid0 multipath linear md_mod dm_mod sr_mod cdrom sd_mod hid_generic usbhid hid crc32c_intel ahci libahci psmouse libata scsi_mod i2c_i801 sdhci_pci sdhci firewire_ohci firewire_core mmc_core crc_itu_t ehci_pci ehci_hcd e1000e ptp usbcore pps_core thermal
Jan 25 12:05:58 merkaba kernel: [10113.919216] CPU: 0 PID: 8474 Comm: kworker/0:2 Tainted: G        W  O    4.10.0-rc5-tp520+ #78
Jan 25 12:05:58 merkaba kernel: [10113.919218] Hardware name: LENOVO 42433WG/42433WG, BIOS 8AET63WW (1.43 ) 05/08/2013
Jan 25 12:05:58 merkaba kernel: [10113.919223] Workqueue: events __i915_gem_free_work
Jan 25 12:05:58 merkaba kernel: [10113.919225] Call Trace:
Jan 25 12:05:58 merkaba kernel: [10113.919233]  dump_stack+0x4d/0x63
Jan 25 12:05:58 merkaba kernel: [10113.919237]  __warn+0xcb/0xf0
Jan 25 12:05:58 merkaba kernel: [10113.919239]  warn_slowpath_fmt+0x4f/0x60
Jan 25 12:05:58 merkaba kernel: [10113.919242]  i915_vma_close+0xa3/0xb0
Jan 25 12:05:58 merkaba kernel: [10113.919246]  __i915_gem_free_objects+0x86/0x350
Jan 25 12:05:58 merkaba kernel: [10113.919249]  __i915_gem_free_work+0x33/0x50
Jan 25 12:05:58 merkaba kernel: [10113.919253]  process_one_work+0x1de/0x4c0
Jan 25 12:05:58 merkaba kernel: [10113.919256]  worker_thread+0x48/0x4e0
Jan 25 12:05:58 merkaba kernel: [10113.919259]  kthread+0x101/0x140
Jan 25 12:05:58 merkaba kernel: [10113.919262]  ? process_one_work+0x4c0/0x4c0
Jan 25 12:05:58 merkaba kernel: [10113.919265]  ? kthread_create_on_node+0x40/0x40
Jan 25 12:05:58 merkaba kernel: [10113.919269]  ret_from_fork+0x29/0x40
Jan 25 12:05:58 merkaba kernel: [10113.919271] ---[ end trace 9761d36f6e68dba8 ]---
Jan 25 12:05:58 merkaba kernel: [10113.919343] ------------[ cut here ]------------
Jan 25 12:05:58 merkaba kernel: [10113.919355] WARNING: CPU: 0 PID: 8474 at drivers/gpu/drm/i915/i915_gem.c:4101 __i915_gem_free_objects+0x303/0x350
Jan 25 12:05:58 merkaba kernel: [10113.919360] WARN_ON(i915_gem_object_has_pinned_pages(obj))
Jan 25 12:05:58 merkaba kernel: [10113.919362] Modules linked in: acpi_call(O) pci_stub vboxpci(O) vboxnetadp(O) vboxnetflt(O) vboxdrv(O) xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp tun bridge stp llc snd_usb_audio snd_usbmidi_lib snd_rawmidi snd_seq_device ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter uinput binfmt_misc nls_utf8 nls_cp437 vfat fat ext4 crc16 jbd2 fscrypto mbcache intel_rapl iosf_mbi x86_pkg_temp_thermal intel_powerclamp kvm_intel kvm irqbypass crct10dif_pclmul crc32_pclmul ghash_clmulni_intel pcbc snd_hda_codec_hdmi snd_hda_codec_conexant snd_hda_codec_generic iwldvm mac80211 aesni_intel aes_x86_64 crypto_simd glue_helper cryptd pcspkr serio_raw iwlwifi sg cfg80211
Jan 25 12:05:58 merkaba kernel: [10113.919508]  lpc_ich mfd_core snd_hda_intel snd_hda_codec shpchp snd_hwdep snd_hda_core mei_me thinkpad_acpi mei snd_pcm snd_timer nvram snd soundcore rfkill battery ac tpm_tis tpm_tis_core tpm evdev joydev sbs sbshc coretemp hdaps(O) tp_smapi(O) thinkpad_ec(O) loop firewire_sbp2 ecryptfs cbc hmac encrypted_keys sunrpc ip_tables x_tables autofs4 btrfs raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c crc32c_generic raid1 raid0 multipath linear md_mod dm_mod sr_mod cdrom sd_mod hid_generic usbhid hid crc32c_intel ahci libahci psmouse libata scsi_mod i2c_i801 sdhci_pci sdhci firewire_ohci firewire_core mmc_core crc_itu_t ehci_pci ehci_hcd e1000e ptp usbcore pps_core thermal
Jan 25 12:05:58 merkaba kernel: [10113.919630] CPU: 0 PID: 8474 Comm: kworker/0:2 Tainted: G        W  O    4.10.0-rc5-tp520+ #78
Jan 25 12:05:58 merkaba kernel: [10113.919635] Hardware name: LENOVO 42433WG/42433WG, BIOS 8AET63WW (1.43 ) 05/08/2013
Jan 25 12:05:58 merkaba kernel: [10113.919646] Workqueue: events __i915_gem_free_work
Jan 25 12:05:58 merkaba kernel: [10113.919651] Call Trace:
Jan 25 12:05:58 merkaba kernel: [10113.919661]  dump_stack+0x4d/0x63
Jan 25 12:05:58 merkaba kernel: [10113.919669]  __warn+0xcb/0xf0
Jan 25 12:05:58 merkaba kernel: [10113.919679]  ? dma_fence_context_alloc+0x20/0x20
Jan 25 12:05:58 merkaba kernel: [10113.919688]  warn_slowpath_fmt+0x4f/0x60
Jan 25 12:05:58 merkaba kernel: [10113.919698]  __i915_gem_free_objects+0x303/0x350
Jan 25 12:05:58 merkaba kernel: [10113.919706]  __i915_gem_free_work+0x33/0x50
Jan 25 12:05:58 merkaba kernel: [10113.919715]  process_one_work+0x1de/0x4c0
Jan 25 12:05:58 merkaba kernel: [10113.919725]  worker_thread+0x48/0x4e0
Jan 25 12:05:58 merkaba kernel: [10113.919732]  kthread+0x101/0x140
Jan 25 12:05:58 merkaba kernel: [10113.919741]  ? process_one_work+0x4c0/0x4c0
Jan 25 12:05:58 merkaba kernel: [10113.919749]  ? kthread_create_on_node+0x40/0x40
Jan 25 12:05:58 merkaba kernel: [10113.919757]  ret_from_fork+0x29/0x40
Jan 25 12:05:58 merkaba kernel: [10113.919765] ---[ end trace 9761d36f6e68dba9 ]---
Jan 25 12:05:58 merkaba sddm[1898]: Display server stopped.
Jan 25 12:05:58 merkaba sddm[1898]: Running display stop script  "/usr/share/sddm/scripts/Xstop"
Jan 25 12:05:58 merkaba sddm[1898]: Socket server stopping...
Jan 25 12:05:58 merkaba sddm[1898]: Socket server stopped.
Jan 25 12:05:58 merkaba sddm[1898]: Removing display ":1" ...

I wonder about the sddm messages. Maybe the traces just appeared as I typed "reboot" via SSH from another laptop, but not before.

The black screen might be due to the GPU hang in combination with Plasma screen lock handling. When I press Ctrl-Alt-L kwin locks the screen, but there is a certain delay sometimes. When I switch to user session before the lock screen appears, display on original TTY seems to be frozen (maybe due to systemd-logind session handling). When I then switch back I have a black screen for a short moment, but then it displays the lockscreen.

# Expected results
Either lockscreen or content of other session displayed.