[  622.580106]
[  622.581632] =========================================================
[  622.588063] [ INFO: possible irq lock inversion dependency detected ]
[  622.594498] 3.19.0-rc1-ARCH+ #1 Not tainted
[  622.598681] ---------------------------------------------------------
[  622.605112] kworker/0:1/162 just changed the state of lock:
[  622.610674]  (&(&blkcg->lock)->rlock){+.+...}, at: [<c03a8f80>] blkcg_css_offline+0x48/0x60
[  622.619135] but this lock was taken by another, SOFTIRQ-safe lock in the past:
[  622.626345]  (&(&q->__queue_lock)->rlock){+.-...}

and interrupts could create inverse lock ordering between them.

[  622.637078]
[  622.637078] other info that might help us debug this:
[  622.643601]  Possible interrupt unsafe locking scenario:
[  622.643601]
[  622.650381]        CPU0                    CPU1
[  622.654909]        ----                    ----
[  622.659435]   lock(&(&blkcg->lock)->rlock);
[  622.663663]                                local_irq_disable();
[  622.669570]                                lock(&(&q->__queue_lock)->rlock);
[  622.676639]                                lock(&(&blkcg->lock)->rlock);
[  622.683369]   <Interrupt>
[  622.685994]     lock(&(&q->__queue_lock)->rlock);
[  622.690739]
[  622.690739]  *** DEADLOCK ***
[  622.690739]
[  622.696664] 5 locks held by kworker/0:1/162:
[  622.700935]  #0:  ("cgroup_destroy"){.+.+..}, at: [<c0031578>] process_one_work+0x198/0x55c
[  622.709377]  #1:  ((&css->destroy_work)#3){+.+...}, at: [<c0031578>] process_one_work+0x198/0x55c
[  622.718345]  #2:  (cgroup_mutex){+.+.+.}, at: [<c007f05c>] css_killed_work_fn+0x18/0x1b4
[  622.726519]  #3:  (&(&blkcg->lock)->rlock){+.+...}, at: [<c03a8f80>] blkcg_css_offline+0x48/0x60
[  622.735392]  #4:  (&(&q->__queue_lock)->rlock){+.-...}, at: [<c03a8f54>] blkcg_css_offline+0x1c/0x60
[  622.744621]
[  622.744621] the shortest dependencies between 2nd lock and 1st lock:
[  622.752482]  -> (&(&q->__queue_lock)->rlock){+.-...} ops: 16731 {
[  622.758669]     HARDIRQ-ON-W at:
[  622.761917]                       [<c03ae480>] cfqg_stats_merge+0x3c/0x2a0
[  622.768821]                       [<c03b0334>] cfq_pd_offline+0xa4/0xe8
[  622.775465]                       [<c03a8d6c>] blkg_destroy+0x108/0x238
[  622.782109]                       [<c03a8f64>] blkcg_css_offline+0x2c/0x60
[  622.789012]                       [<c007f0a0>] css_killed_work_fn+0x5c/0x1b4
[  622.796080]                       [<c0031684>] process_one_work+0x2a4/0x55c
[  622.803069]                       [<c0031c10>] worker_thread+0x2a8/0x42c
[  622.809791]                       [<c003573c>] kthread+0xc0/0xd4
[  622.815822]                       [<c00094a0>] ret_from_fork+0x14/0x34
[  622.822373]     IN-SOFTIRQ-W at:
[  622.825620]                       [<c06f09a4>] _raw_spin_lock_irqsave+0x44/0x58
[  622.832946]                       [<c046dc30>] scsi_end_request+0x114/0x15c
[  622.839927]                       [<c046f280>] scsi_io_completion+0x1c0/0x50c
[  622.847073]                       [<c03981e8>] blk_done_softirq+0x78/0x8c
[  622.853890]                       [<c001f0f8>] __do_softirq+0x1a8/0x448
[  622.860533]                       [<c001f3c4>] run_ksoftirqd+0x2c/0x60
[  622.867074]                       [<c0038e8c>] smpboot_thread_fn+0x284/0x298
[  622.874150]                       [<c003573c>] kthread+0xc0/0xd4
[  622.880172]                       [<c00094a0>] ret_from_fork+0x14/0x34
[  622.886715]     INITIAL USE at:
[  622.889875]                      [<c06f0a00>] _raw_spin_lock_irq+0x48/0x58
[  622.896769]                      [<c0390130>] blk_queue_bypass_start+0x10/0xa8
[  622.904027]                      [<c03a9fc0>] blkcg_activate_policy+0x4c/0x2f4
[  622.911267]                      [<c03ad508>] blk_throtl_init+0xa8/0xec
[  622.917894]                      [<c038fdb0>] blk_alloc_queue_node+0x1ac/0x220
[  622.925135]                      [<c04610b0>] loop_add+0x84/0x1ec
[  622.931261]                      [<c09f6a90>] loop_init+0xcc/0x124
[  622.937473]                      [<c00088a0>] do_one_initcall+0xf8/0x1d0
[  622.944186]                      [<c09c8e7c>] kernel_init_freeable+0x1d4/0x2a4
[  622.951436]                      [<c06e4534>] kernel_init+0x8/0xe4
[  622.957656]                      [<c00094a0>] ret_from_fork+0x14/0x34
[  622.964119]   }
[  622.965880]   ... key      at: [<c1275418>] __key.36420+0x0/0x8
[  622.971827]   ... acquired at:
[  622.974882]    [<c0390130>] blk_queue_bypass_start+0x10/0xa8
[  622.980578]    [<c03a9fc0>] blkcg_activate_policy+0x4c/0x2f4
[  622.986262]    [<c03ad508>] blk_throtl_init+0xa8/0xec
[  622.991334]    [<c038fdb0>] blk_alloc_queue_node+0x1ac/0x220
[  622.997019]    [<c04610b0>] loop_add+0x84/0x1ec
[  623.001572]    [<c09f6a90>] loop_init+0xcc/0x124
[  623.006212]    [<c00088a0>] do_one_initcall+0xf8/0x1d0
[  623.011370]    [<c09c8e7c>] kernel_init_freeable+0x1d4/0x2a4
[  623.017047]    [<c06e4534>] kernel_init+0x8/0xe4
[  623.021704]    [<c00094a0>] ret_from_fork+0x14/0x34
[  623.026602]
[  623.028106] -> (&(&blkcg->lock)->rlock){+.+...} ops: 42 {
[  623.033594]    HARDIRQ-ON-W at:
[  623.036755]                     [<c03ae480>] cfqg_stats_merge+0x3c/0x2a0
[  623.043470]                     [<c03b0334>] cfq_pd_offline+0xa4/0xe8
[  623.049932]                     [<c03a8d6c>] blkg_destroy+0x108/0x238
[  623.056403]                     [<c03a8f64>] blkcg_css_offline+0x2c/0x60
[  623.063133]                     [<c007f0a0>] css_killed_work_fn+0x5c/0x1b4
[  623.070036]                     [<c0031684>] process_one_work+0x2a4/0x55c
[  623.076844]                     [<c0031c10>] worker_thread+0x2a8/0x42c
[  623.083386]                     [<c003573c>] kthread+0xc0/0xd4
[  623.089242]                     [<c00094a0>] ret_from_fork+0x14/0x34
[  623.095612]    SOFTIRQ-ON-W at:
[  623.098773]                     [<c03ae480>] cfqg_stats_merge+0x3c/0x2a0
[  623.105487]                     [<c03b0334>] cfq_pd_offline+0xa4/0xe8
[  623.111940]                     [<c03a8d6c>] blkg_destroy+0x108/0x238
[  623.118403]                     [<c03a8f64>] blkcg_css_offline+0x2c/0x60
[  623.125134]                     [<c007f0a0>] css_killed_work_fn+0x5c/0x1b4
[  623.132028]                     [<c0031684>] process_one_work+0x2a4/0x55c
[  623.138837]                     [<c0031c10>] worker_thread+0x2a8/0x42c
[  623.145386]                     [<c003573c>] kthread+0xc0/0xd4
[  623.151235]                     [<c00094a0>] ret_from_fork+0x14/0x34
[  623.157604]    INITIAL USE at:
[  623.160679]                    [<c06f08c0>] _raw_spin_lock+0x38/0x48
[  623.167055]                    [<c03a9cd0>] blkg_create+0x274/0x518
[  623.173345]                    [<c03aa030>] blkcg_activate_policy+0xbc/0x2f4
[  623.180421]                    [<c03ad508>] blk_throtl_init+0xa8/0xec
[  623.186875]                    [<c038fdb0>] blk_alloc_queue_node+0x1ac/0x220
[  623.193952]                    [<c04610b0>] loop_add+0x84/0x1ec
[  623.199905]                    [<c09f6a90>] loop_init+0xcc/0x124
[  623.205943]                    [<c00088a0>] do_one_initcall+0xf8/0x1d0
[  623.212484]                    [<c09c8e7c>] kernel_init_freeable+0x1d4/0x2a4
[  623.219543]                    [<c06e4534>] kernel_init+0x8/0xe4
[  623.225583]                    [<c00094a0>] ret_from_fork+0x14/0x34
[  623.231873]  }
[  623.233548]  ... key      at: [<c12759ec>] __key.30063+0x0/0x8
[  623.239407]  ... acquired at:
[  623.242376]    [<c004eb28>] mark_held_locks+0x64/0x84
[  623.247467]    [<c004ec94>] trace_hardirqs_on_caller+0x14c/0x1e8
[  623.253498]    [<c03ae480>] cfqg_stats_merge+0x3c/0x2a0
[  623.258742]    [<c03b0334>] cfq_pd_offline+0xa4/0xe8
[  623.263727]    [<c03a8d6c>] blkg_destroy+0x108/0x238
[  623.268721]    [<c03a8f64>] blkcg_css_offline+0x2c/0x60
[  623.273974]    [<c007f0a0>] css_killed_work_fn+0x5c/0x1b4
[  623.279400]    [<c0031684>] process_one_work+0x2a4/0x55c
[  623.284740]    [<c0031c10>] worker_thread+0x2a8/0x42c
[  623.289811]    [<c003573c>] kthread+0xc0/0xd4
[  623.294192]    [<c00094a0>] ret_from_fork+0x14/0x34
[  623.299091]
[  623.300594]
[  623.300594] stack backtrace:
[  623.304970] CPU: 0 PID: 162 Comm: kworker/0:1 Not tainted 3.19.0-rc1-ARCH+ #1
[  623.312097] Hardware name: Marvell Orion5x (Flattened Device Tree)
[  623.318281] Workqueue: cgroup_destroy css_killed_work_fn
[  623.323645] [<c000e068>] (unwind_backtrace) from [<c000bd84>] (show_stack+0x10/0x14)
[  623.331413] [<c000bd84>] (show_stack) from [<c06e63a4>] (print_irq_inversion_bug.part.24+0x170/0x1a8)
[  623.340654] [<c06e63a4>] (print_irq_inversion_bug.part.24) from [<c004b564>] (check_usage_backwards+0x10c/0x148)
[  623.350837] [<c004b564>] (check_usage_backwards) from [<c004c3dc>] (mark_lock+0x600/0x660)
[  623.359120] [<c004c3dc>] (mark_lock) from [<c004eb28>] (mark_held_locks+0x64/0x84)
[  623.366709] [<c004eb28>] (mark_held_locks) from [<c004ec94>] (trace_hardirqs_on_caller+0x14c/0x1e8)
[  623.375771] [<c004ec94>] (trace_hardirqs_on_caller) from [<c03ae480>] (cfqg_stats_merge+0x3c/0x2a0)
[  623.384820] [<c03ae480>] (cfqg_stats_merge) from [<c03b0334>] (cfq_pd_offline+0xa4/0xe8)
[  623.392928] [<c03b0334>] (cfq_pd_offline) from [<c03a8d6c>] (blkg_destroy+0x108/0x238)
[  623.400863] [<c03a8d6c>] (blkg_destroy) from [<c03a8f64>] (blkcg_css_offline+0x2c/0x60)
[  623.408891] [<c03a8f64>] (blkcg_css_offline) from [<c007f0a0>] (css_killed_work_fn+0x5c/0x1b4)
[  623.417516] [<c007f0a0>] (css_killed_work_fn) from [<c0031684>] (process_one_work+0x2a4/0x55c)
[  623.426140] [<c0031684>] (process_one_work) from [<c0031c10>] (worker_thread+0x2a8/0x42c)
[  623.434327] [<c0031c10>] (worker_thread) from [<c003573c>] (kthread+0xc0/0xd4)
[  623.441564] [<c003573c>] (kthread) from [<c00094a0>] (ret_from_fork+0x14/0x34)