Recompiled kernel with lockdep enabled gives me this:

=3D=3D=3D
[  368.655051] Showing all locks held in the system:
[  368.656387] 1 lock held by khungtaskd/37:
[  368.657171]  #0:  (tasklist_lock){.+.+..}, at: [<ffffffffa90c801d>]=20
debug_show_all_locks+0x3d/0x1a0
[  368.658725] 1 lock held by md0_raid10/458:
[  368.659455]  #0:  (&mddev->reconfig_mutex){+.+.+.}, at:=20
[<ffffffffc036790f>] md_check_recovery+0xaf/0x4d0 [md_mod]
[  368.661403] 3 locks held by btrfs-transacti/550:
[  368.662754]  #0:  (&fs_info->transaction_kthread_mutex){+.+...}, at:=20
[<ffffffffc03eeb79>] transaction_kthread+0x69/0x1c0 [btrfs]
[  368.664797]  #1:  (&fs_info->reloc_mutex){+.+...}, at: [<ffffffffc03f457=
1>]=20
btrfs_commit_transaction+0x2e1/0x9b0 [btrfs]
[  368.666669]  #2:  (&fs_info->tree_log_mutex){+.+...}, at:=20
[<ffffffffc03f45e1>] btrfs_commit_transaction+0x351/0x9b0 [btrfs]
[  368.668644] 4 locks held by kworker/0:2/888:
[  368.669384]  #0:  ("events"){.+.+.+}, at: [<ffffffffa90abd0b>]=20
process_one_work+0x1fb/0x6e0
[  368.670916]  #1:  ((shepherd).work){+.+...}, at: [<ffffffffa90abd0b>]=20
process_one_work+0x1fb/0x6e0
[  368.672592]  #2:  (cpu_hotplug.dep_map){++++++}, at: [<ffffffffa908c245>=
]=20
get_online_cpus.part.14+0x5/0x50
[  368.674742]  #3:  (cpu_hotplug.lock){+.+.+.}, at: [<ffffffffa908c27a>]=20
get_online_cpus.part.14+0x3a/0x50
[  368.677494] 10 locks held by systemd-sleep/889:
[  368.678650]  #0:  (sb_writers#5){.+.+.+}, at: [<ffffffffa924779b>]=20
vfs_write+0x17b/0x1a0
[  368.680483]  #1:  (&of->mutex){+.+.+.}, at: [<ffffffffa92db703>]=20
kernfs_fop_write+0x123/0x1e0
[  368.682412]  #2:  (s_active#257){.+.+.+}, at: [<ffffffffa92db70c>]=20
kernfs_fop_write+0x12c/0x1e0
[  368.684440]  #3:  (autosleep_lock){+.+.+.}, at: [<ffffffffa90da3b7>]=20
pm_autosleep_lock+0x17/0x20
[  368.686707]  #4:  (pm_mutex){+.+.+.}, at: [<ffffffffa90d28f8>] pm_suspend
+0x88/0x490
[  368.688086]  #5:  (acpi_scan_lock){+.+.+.}, at: [<ffffffffa941c907>]=20
acpi_scan_lock_acquire+0x17/0x20
[  368.690213]  #6:  (cpu_add_remove_lock){+.+.+.}, at: [<ffffffffa908e160>=
]=20
freeze_secondary_cpus+0x30/0x3c0
[  368.692016]  #7:  (cpu_hotplug.dep_map){++++++}, at: [<ffffffffa908da75>=
]=20
cpu_hotplug_begin+0x5/0xe0
[  368.694347]  #8:  (cpu_hotplug.lock){+.+.+.}, at: [<ffffffffa908daf3>]=20
cpu_hotplug_begin+0x83/0xe0
[  368.696010]  #9:  (all_q_mutex){+.+...}, at: [<ffffffffa933e05a>]=20
blk_mq_queue_reinit_work+0x1a/0x110
[  368.698624]=20
[  368.698990] =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
[  368.698990]
=3D=3D=3D

Deadlock with CPU hotplug?

On sobota 29. =C4=8Dervence 2017 17:27:41 CEST Oleksandr Natalenko wrote:

Hello Jens, Christoph.
=20
Unfortunately, even with "block: disable runtime-pm for blk-mq" patch
applied blk-mq breaks suspend to RAM for me. It is reproducible on my
laptop as well as in a VM.
=20
I use complex disk layout involving MD, LUKS and LVM, and managed to get
these warnings from VM via serial console when suspend fails:
=20
=3D=3D=3D
[  245.516573] INFO: task kworker/0:1:49 blocked for more than 120 second=

s.

[  245.520025]       Not tainted 4.12.0-pf4 #1
[  245.521836] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables
this message.
[  245.525612] kworker/0:1     D    0    49      2 0x00000000
[  245.527515] Workqueue: events vmstat_shepherd
[  245.528685] Call Trace:
[  245.529296]  __schedule+0x459/0xe40
[  245.530115]  ? kvm_clock_read+0x25/0x40
[  245.531003]  ? ktime_get+0x40/0xa0
[  245.531819]  schedule+0x3d/0xb0
[  245.532542]  ? schedule+0x3d/0xb0
[  245.533299]  schedule_preempt_disabled+0x15/0x20
[  245.534367]  __mutex_lock.isra.5+0x295/0x530
[  245.535351]  __mutex_lock_slowpath+0x13/0x20
[  245.536362]  ? __mutex_lock_slowpath+0x13/0x20
[  245.537334]  mutex_lock+0x25/0x30
[  245.538118]  get_online_cpus.part.14+0x15/0x30
[  245.539588]  get_online_cpus+0x20/0x30
[  245.540560]  vmstat_shepherd+0x21/0xc0
[  245.541538]  process_one_work+0x1de/0x430
[  245.542364]  worker_thread+0x47/0x3f0
[  245.543042]  kthread+0x125/0x140
[  245.543649]  ? process_one_work+0x430/0x430
[  245.544417]  ? kthread_create_on_node+0x70/0x70
[  245.545737]  ret_from_fork+0x25/0x30
[  245.546490] INFO: task md0_raid10:459 blocked for more than 120 second=

s.

[  245.547668]       Not tainted 4.12.0-pf4 #1
[  245.548769] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables
this message.
[  245.550133] md0_raid10      D    0   459      2 0x00000000
[  245.551092] Call Trace:
[  245.551539]  __schedule+0x459/0xe40
[  245.552163]  schedule+0x3d/0xb0
[  245.552728]  ? schedule+0x3d/0xb0
[  245.553344]  md_super_wait+0x6e/0xa0 [md_mod]
[  245.554118]  ? wake_bit_function+0x60/0x60
[  245.554854]  md_update_sb.part.60+0x3df/0x840 [md_mod]
[  245.555771]  md_check_recovery+0x215/0x4b0 [md_mod]
[  245.556732]  raid10d+0x62/0x13c0 [raid10]
[  245.557456]  ? schedule+0x3d/0xb0
[  245.558169]  ? schedule+0x3d/0xb0
[  245.558803]  ? schedule_timeout+0x21f/0x330
[  245.559593]  md_thread+0x120/0x160 [md_mod]
[  245.560380]  ? md_thread+0x120/0x160 [md_mod]
[  245.561202]  ? wake_bit_function+0x60/0x60
[  245.561975]  kthread+0x125/0x140
[  245.562601]  ? find_pers+0x70/0x70 [md_mod]
[  245.563394]  ? kthread_create_on_node+0x70/0x70
[  245.564516]  ret_from_fork+0x25/0x30
[  245.565669] INFO: task dmcrypt_write:487 blocked for more than 120
seconds. [  245.567151]       Not tainted 4.12.0-pf4 #1
[  245.567946] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables
this message.
[  245.569390] dmcrypt_write   D    0   487      2 0x00000000
[  245.570352] Call Trace:
[  245.570801]  __schedule+0x459/0xe40
[  245.571601]  ? preempt_schedule_common+0x1f/0x30
[  245.572421]  ? ___preempt_schedule+0x16/0x18
[  245.573168]  schedule+0x3d/0xb0
[  245.573733]  ? schedule+0x3d/0xb0
[  245.574378]  md_write_start+0xe3/0x270 [md_mod]
[  245.575180]  ? wake_bit_function+0x60/0x60
[  245.575915]  raid10_make_request+0x3f/0x140 [raid10]
[  245.576827]  md_make_request+0xa9/0x2a0 [md_mod]
[  245.577659]  generic_make_request+0x11e/0x2f0
[  245.578464]  dmcrypt_write+0x22d/0x250 [dm_crypt]
[  245.579288]  ? dmcrypt_write+0x22d/0x250 [dm_crypt]
[  245.580183]  ? wake_up_process+0x20/0x20
[  245.580875]  kthread+0x125/0x140
[  245.581455]  ? kthread+0x125/0x140
[  245.582064]  ? crypt_iv_essiv_dtr+0x70/0x70 [dm_crypt]
[  245.582971]  ? kthread_create_on_node+0x70/0x70
[  245.583772]  ret_from_fork+0x25/0x30
[  245.584424] INFO: task btrfs-transacti:553 blocked for more than 120
seconds.
[  245.585830]       Not tainted 4.12.0-pf4 #1
[  245.586596] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables
this message.
[  245.587947] btrfs-transacti D    0   553      2 0x00000000
[  245.588922] Call Trace:
[  245.589377]  __schedule+0x459/0xe40
[  245.590062]  ? btrfs_submit_bio_hook+0x8c/0x180 [btrfs]
[  245.590976]  schedule+0x3d/0xb0
[  245.591538]  ? schedule+0x3d/0xb0
[  245.592175]  io_schedule+0x16/0x40
[  245.592794]  wait_on_page_bit_common+0xe3/0x180
[  245.593589]  ? page_cache_tree_insert+0xc0/0xc0
[  245.594387]  __filemap_fdatawait_range+0x12a/0x1a0
[  245.595229]  filemap_fdatawait_range+0x14/0x30
[  245.596033]  btrfs_wait_ordered_range+0x6b/0x110 [btrfs]
[  245.596998]  ? _raw_spin_unlock+0x10/0x30
[  245.597735]  __btrfs_wait_cache_io+0x45/0x1c0 [btrfs]
[  245.599091]  btrfs_wait_cache_io+0x2c/0x30 [btrfs]
[  245.600789]  btrfs_write_dirty_block_groups+0x206/0x390 [btrfs]
[  245.602068]  commit_cowonly_roots+0x221/0x2c0 [btrfs]
[  245.602981]  btrfs_commit_transaction+0x3c4/0x900 [btrfs]
[  245.603940]  transaction_kthread+0x190/0x1c0 [btrfs]
[  245.604806]  kthread+0x125/0x140
[  245.605398]  ? btrfs_cleanup_transaction+0x500/0x500 [btrfs]
[  245.606414]  ? kthread_create_on_node+0x70/0x70
[  245.607213]  ret_from_fork+0x25/0x30
[  245.607846] INFO: task systemd-sleep:677 blocked for more than 120
seconds. [  245.609061]       Not tainted 4.12.0-pf4 #1
[  245.609858] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables
this message.
[  245.611202] systemd-sleep   D    0   677      1 0x00000000
[  245.612160] Call Trace:
[  245.612604]  __schedule+0x459/0xe40
[  245.613231]  ? blk_mq_queue_reinit_work+0x100/0x100
[  245.614080]  schedule+0x3d/0xb0
[  245.614637]  ? schedule+0x3d/0xb0
[  245.615222]  blk_mq_freeze_queue_wait+0x46/0xb0
[  245.616015]  ? wake_bit_function+0x60/0x60
[  245.616778]  blk_mq_queue_reinit_work+0x6e/0x100
[  245.617592]  blk_mq_queue_reinit_dead+0x3d/0x50
[  245.618420]  ? __flow_cache_shrink+0x170/0x170
[  245.619199]  cpuhp_invoke_callback+0x84/0x430
[  245.619965]  ? cpuhp_invoke_callback+0x84/0x430
[  245.620754]  ? __flow_cache_shrink+0x170/0x170
[  245.621530]  cpuhp_down_callbacks+0x42/0x80
[  245.622267]  _cpu_down+0xc5/0x100
[  245.622856]  freeze_secondary_cpus+0x9e/0x230
[  245.623629]  suspend_devices_and_enter+0x2e6/0x800
[  245.624471]  pm_suspend+0x349/0x3c0
[  245.625090]  state_store+0x49/0xa0
[  245.625699]  kobj_attr_store+0xf/0x20
[  245.626379]  sysfs_kf_write+0x37/0x40
[  245.627038]  kernfs_fop_write+0x11c/0x1a0
[  245.627800]  __vfs_write+0x37/0x140
[  245.628448]  ? handle_mm_fault+0xde/0x220
[  245.629155]  vfs_write+0xb1/0x1a0
[  245.629745]  SyS_write+0x55/0xc0
[  245.630337]  ? trace_do_page_fault+0x37/0xf0
[  245.631088]  entry_SYSCALL_64_fastpath+0x1a/0xa5
[  245.632109] RIP: 0033:0x7f810459dbf0
[  245.632821] RSP: 002b:00007ffec9ba2e58 EFLAGS: 00000246 ORIG_RAX:
0000000000000001
[  245.634127] RAX: ffffffffffffffda RBX: 00000000000000c6 RCX:
00007f810459dbf0
[  245.635353] RDX: 0000000000000004 RSI: 000000b716c73390 RDI:
0000000000000004
[  245.636778] RBP: 000000000000270f R08: 000000b716c73240 R09:
00007f8104a718c0
[  245.638254] R10: 00007f810485ead8 R11: 0000000000000246 R12:
00007f810485ead8
[  245.639500] R13: 0000000000001010 R14: 000000b716c73380 R15:
00007f810485ea80
=3D=3D=3D
=20
With blk-mq disabled everything works okay.
=20
How can I help you in solving this issue?