FS-Cache: N-cookie c=000000000f6d2185 [p=00000000502e15e3 fl=2 nc=0 na=1]
FS-Cache: N-cookie d=0000000070654a6d n=00000000301bc34d
FS-Cache: N-key=[10] '0200020000807f000008'
------------[ cut here ]------------
ODEBUG: free active (active state 0) object type: timer_list hint: xprt_init_autodisconnect+0x0/0x230 net/sunrpc/xprt.c:109
WARNING: CPU: 0 PID: 0 at lib/debugobjects.c:328 debug_print_object+0x16a/0x210 lib/debugobjects.c:325
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.20.0-rc7+ #375
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x244/0x39d lib/dump_stack.c:113
 panic+0x2ad/0x55c kernel/panic.c:188
 __warn.cold.8+0x20/0x45 kernel/panic.c:540
 report_bug+0x254/0x2d0 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:178 [inline]
 do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271
 do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:290
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973
RIP: 0010:debug_print_object+0x16a/0x210 lib/debugobjects.c:325
Code: 60 88 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 92 00 00 00 48 8b 14 dd 60 e0 60 88 4c 89 fe 48 c7 c7 00 d6 60 88 e8 36 a1 b5 fd <0f> 0b 83 05 81 30 83 06 01 48 83 c4 18 5b 41 5c 41 5d 41 5e 41 5f
RSP: 0018:ffff8881dae07578 EFLAGS: 00010082
kobject: 'loop1' (000000003b9f69d4): kobject_uevent_env
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000000000
RDX: 0000000000000100 RSI: ffffffff8165e495 RDI: 0000000000000005
RBP: ffff8881dae075b8 R08: ffffffff89476ec0 R09: ffffed103b5c3ef8
R10: ffffed103b5c3ef8 R11: ffff8881dae1f7c7 R12: 0000000000000001
R13: ffffffff895a5980 R14: ffffffff816c2760 R15: ffffffff8860daa0
kobject: 'loop1' (000000003b9f69d4): fill_kobj_path: path = '/devices/virtual/block/loop1'
 __debug_check_no_obj_freed lib/debugobjects.c:785 [inline]
 debug_check_no_obj_freed+0x3ae/0x58d lib/debugobjects.c:817
 kfree+0xbd/0x230 mm/slab.c:3816
 __rcu_reclaim kernel/rcu/rcu.h:233 [inline]
 rcu_do_batch kernel/rcu/tree.c:2437 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2716 [inline]
 rcu_process_callbacks+0x1140/0x1ac0 kernel/rcu/tree.c:2697
 __do_softirq+0x308/0xb7e kernel/softirq.c:292
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0x17f/0x1c0 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:536 [inline]
 smp_apic_timer_interrupt+0x1cb/0x760 arch/x86/kernel/apic/apic.c:1061
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:807
 </IRQ>
RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:58
Code: e9 2c ff ff ff 48 89 c7 48 89 45 d8 e8 33 c1 e7 f9 48 8b 45 d8 e9 ca fe ff ff 48 89 df e8 22 c1 e7 f9 eb 82 55 48 89 e5 fb f4 <5d> c3 0f 1f 84 00 00 00 00 00 55 48 89 e5 f4 5d c3 90 90 90 90 90
RSP: 0018:ffffffff89407c10 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
RAX: dffffc0000000000 RBX: 1ffffffff1280f86 RCX: 0000000000000000
RDX: 1ffffffff12a4021 RSI: 0000000000000001 RDI: ffffffff89520108
RBP: ffffffff89407c10 R08: ffffffff89476ec0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff89407cd0
R13: ffffffff8a1641a0 R14: 0000000000000000 R15: 0000000000000000
 arch_safe_halt arch/x86/include/asm/paravirt.h:151 [inline]
 default_idle+0xbf/0x490 arch/x86/kernel/process.c:561
 arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:552
 default_idle_call+0x6d/0x90 kernel/sched/idle.c:93
 cpuidle_idle_call kernel/sched/idle.c:153 [inline]
 do_idle+0x49b/0x5c0 kernel/sched/idle.c:262
 cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:353
 rest_init+0x243/0x372 init/main.c:443
 arch_call_rest_init+0xe/0x1b
 start_kernel+0x9f5/0xa30 init/main.c:745
 x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:470
 x86_64_start_kernel+0x76/0x79 arch/x86/kernel/head64.c:451
 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

======================================================
WARNING: possible circular locking dependency detected
4.20.0-rc7+ #375 Not tainted
------------------------------------------------------
swapper/0/0 is trying to acquire lock:
0000000090397a1f ((console_sem).lock){-.-.}, at: down_trylock+0x13/0x70 kernel/locking/semaphore.c:136

but task is already holding lock:
0000000097f9f6ec (&obj_hash[i].lock){-.-.}, at: __debug_check_no_obj_freed lib/debugobjects.c:776 [inline]
0000000097f9f6ec (&obj_hash[i].lock){-.-.}, at: debug_check_no_obj_freed+0x17a/0x58d lib/debugobjects.c:817

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&obj_hash[i].lock){-.-.}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152
       __debug_object_init+0x127/0x1290 lib/debugobjects.c:383
       debug_object_init+0x16/0x20 lib/debugobjects.c:431
       debug_hrtimer_init kernel/time/hrtimer.c:410 [inline]
       debug_init kernel/time/hrtimer.c:458 [inline]
       hrtimer_init+0x97/0x490 kernel/time/hrtimer.c:1308
       init_dl_task_timer+0x1b/0x50 kernel/sched/deadline.c:1057
       __sched_fork+0x2ae/0x590 kernel/sched/core.c:2166
       init_idle+0x75/0x740 kernel/sched/core.c:5374
       sched_init+0xb33/0xc07 kernel/sched/core.c:6063
       start_kernel+0x4c1/0xa30 init/main.c:608
       x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:470
       x86_64_start_kernel+0x76/0x79 arch/x86/kernel/head64.c:451
       secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

-> #2 (&rq->lock){-.-.}:
       __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
       _raw_spin_lock+0x2d/0x40 kernel/locking/spinlock.c:144
       rq_lock kernel/sched/sched.h:1124 [inline]
       task_fork_fair+0xb0/0x6d0 kernel/sched/fair.c:9802
       sched_fork+0x443/0xba0 kernel/sched/core.c:2359
       copy_process+0x25b8/0x87a0 kernel/fork.c:1887
       _do_fork+0x1cb/0x11d0 kernel/fork.c:2216
       kernel_thread+0x34/0x40 kernel/fork.c:2275
       rest_init+0x28/0x372 init/main.c:409
       arch_call_rest_init+0xe/0x1b
       start_kernel+0x9f5/0xa30 init/main.c:745
       x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:470
       x86_64_start_kernel+0x76/0x79 arch/x86/kernel/head64.c:451
       secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

-> #1 (&p->pi_lock){-.-.}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152
       try_to_wake_up+0xdc/0x1440 kernel/sched/core.c:1965
       wake_up_process+0x10/0x20 kernel/sched/core.c:2129
       __up.isra.1+0x1c0/0x2a0 kernel/locking/semaphore.c:262
       up+0x13c/0x1c0 kernel/locking/semaphore.c:187
       __up_console_sem+0xbe/0x1b0 kernel/printk/printk.c:236
       console_unlock+0x811/0x1190 kernel/printk/printk.c:2432
       vprintk_emit+0x391/0x990 kernel/printk/printk.c:1922
       vprintk_default+0x28/0x30 kernel/printk/printk.c:1964
       vprintk_func+0x7e/0x181 kernel/printk/printk_safe.c:398
       printk+0xa7/0xcf kernel/printk/printk.c:1997
       fill_kobj_path lib/kobject.c:151 [inline]
       kobject_get_path.cold.8+0x38/0x47 lib/kobject.c:174
       kobject_uevent_env+0x314/0x101e lib/kobject_uevent.c:519
       call_crda net/wireless/reg.c:556 [inline]
       reg_query_database+0x283/0x400 net/wireless/reg.c:1104
       reg_process_hint_core net/wireless/reg.c:2339 [inline]
       reg_process_hint+0x189/0xec0 net/wireless/reg.c:2677
       reg_process_pending_hints net/wireless/reg.c:2767 [inline]
       reg_todo+0x49a/0xc20 net/wireless/reg.c:2844
       process_one_work+0xc90/0x1c40 kernel/workqueue.c:2153
       worker_thread+0x17f/0x1390 kernel/workqueue.c:2296
       kthread+0x35a/0x440 kernel/kthread.c:246
       ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

-> #0 ((console_sem).lock){-.-.}:
       lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152
       down_trylock+0x13/0x70 kernel/locking/semaphore.c:136
       __down_trylock_console_sem+0xae/0x1f0 kernel/printk/printk.c:219
       console_trylock+0x15/0xa0 kernel/printk/printk.c:2247
       console_trylock_spinning kernel/printk/printk.c:1653 [inline]
       vprintk_emit+0x372/0x990 kernel/printk/printk.c:1921
       vprintk_default+0x28/0x30 kernel/printk/printk.c:1964
       vprintk_func+0x7e/0x181 kernel/printk/printk_safe.c:398
       printk+0xa7/0xcf kernel/printk/printk.c:1997
       __warn_printk+0x8c/0xe0 kernel/panic.c:594
       debug_print_object+0x16a/0x210 lib/debugobjects.c:325
       __debug_check_no_obj_freed lib/debugobjects.c:785 [inline]
       debug_check_no_obj_freed+0x3ae/0x58d lib/debugobjects.c:817
       kfree+0xbd/0x230 mm/slab.c:3816
       __rcu_reclaim kernel/rcu/rcu.h:233 [inline]
       rcu_do_batch kernel/rcu/tree.c:2437 [inline]
       invoke_rcu_callbacks kernel/rcu/tree.c:2716 [inline]
       rcu_process_callbacks+0x1140/0x1ac0 kernel/rcu/tree.c:2697
       __do_softirq+0x308/0xb7e kernel/softirq.c:292
       invoke_softirq kernel/softirq.c:373 [inline]
       irq_exit+0x17f/0x1c0 kernel/softirq.c:413
       exiting_irq arch/x86/include/asm/apic.h:536 [inline]
       smp_apic_timer_interrupt+0x1cb/0x760 arch/x86/kernel/apic/apic.c:1061
       apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:807
       native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:57
       arch_safe_halt arch/x86/include/asm/paravirt.h:151 [inline]
       default_idle+0xbf/0x490 arch/x86/kernel/process.c:561
       arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:552
       default_idle_call+0x6d/0x90 kernel/sched/idle.c:93
       cpuidle_idle_call kernel/sched/idle.c:153 [inline]
       do_idle+0x49b/0x5c0 kernel/sched/idle.c:262
       cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:353
       rest_init+0x243/0x372 init/main.c:443
       arch_call_rest_init+0xe/0x1b
       start_kernel+0x9f5/0xa30 init/main.c:745
       x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:470
       x86_64_start_kernel+0x76/0x79 arch/x86/kernel/head64.c:451
       secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

other info that might help us debug this:

Chain exists of:
  (console_sem).lock --> &rq->lock --> &obj_hash[i].lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&obj_hash[i].lock);
                               lock(&rq->lock);
                               lock(&obj_hash[i].lock);
  lock((console_sem).lock);

 *** DEADLOCK ***

2 locks held by swapper/0/0:
 #0: 0000000096b6ffb2 (rcu_callback){....}, at: __rcu_reclaim kernel/rcu/rcu.h:228 [inline]
 #0: 0000000096b6ffb2 (rcu_callback){....}, at: rcu_do_batch kernel/rcu/tree.c:2437 [inline]
 #0: 0000000096b6ffb2 (rcu_callback){....}, at: invoke_rcu_callbacks kernel/rcu/tree.c:2716 [inline]
 #0: 0000000096b6ffb2 (rcu_callback){....}, at: rcu_process_callbacks+0x1103/0x1ac0 kernel/rcu/tree.c:2697
 #1: 0000000097f9f6ec (&obj_hash[i].lock){-.-.}, at: __debug_check_no_obj_freed lib/debugobjects.c:776 [inline]
 #1: 0000000097f9f6ec (&obj_hash[i].lock){-.-.}, at: debug_check_no_obj_freed+0x17a/0x58d lib/debugobjects.c:817

stack backtrace:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.20.0-rc7+ #375
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x244/0x39d lib/dump_stack.c:113
 print_circular_bug.isra.35.cold.54+0x1bd/0x27d kernel/locking/lockdep.c:1221
 check_prev_add kernel/locking/lockdep.c:1863 [inline]
 check_prevs_add kernel/locking/lockdep.c:1976 [inline]
 validate_chain kernel/locking/lockdep.c:2347 [inline]
 __lock_acquire+0x3399/0x4c20 kernel/locking/lockdep.c:3341
 lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152
 down_trylock+0x13/0x70 kernel/locking/semaphore.c:136
 __down_trylock_console_sem+0xae/0x1f0 kernel/printk/printk.c:219
 console_trylock+0x15/0xa0 kernel/printk/printk.c:2247
 console_trylock_spinning kernel/printk/printk.c:1653 [inline]
 vprintk_emit+0x372/0x990 kernel/printk/printk.c:1921
 vprintk_default+0x28/0x30 kernel/printk/printk.c:1964
 vprintk_func+0x7e/0x181 kernel/printk/printk_safe.c:398
 printk+0xa7/0xcf kernel/printk/printk.c:1997
 __warn_printk+0x8c/0xe0 kernel/panic.c:594
 debug_print_object+0x16a/0x210 lib/debugobjects.c:325
 __debug_check_no_obj_freed lib/debugobjects.c:785 [inline]
 debug_check_no_obj_freed+0x3ae/0x58d lib/debugobjects.c:817
 kfree+0xbd/0x230 mm/slab.c:3816
 __rcu_reclaim kernel/rcu/rcu.h:233 [inline]
 rcu_do_batch kernel/rcu/tree.c:2437 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2716 [inline]
 rcu_process_callbacks+0x1140/0x1ac0 kernel/rcu/tree.c:2697
 __do_softirq+0x308/0xb7e kernel/softirq.c:292
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0x17f/0x1c0 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:536 [inline]
 smp_apic_timer_interrupt+0x1cb/0x760 arch/x86/kernel/apic/apic.c:1061
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:807
 </IRQ>
RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:58
Code: e9 2c ff ff ff 48 89 c7 48 89 45 d8 e8 33 c1 e7 f9 48 8b 45 d8 e9 ca fe ff ff 48 89 df e8 22 c1 e7 f9 eb 82 55 48 89 e5 fb f4 <5d> c3 0f 1f 84 00 00 00 00 00 55 48 89 e5 f4 5d c3 90 90 90 90 90
RSP: 0018:ffffffff89407c10 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
RAX: dffffc0000000000 RBX: 1ffffffff1280f86 RCX: 0000000000000000
RDX: 1ffffffff12a4021 RSI: 0000000000000001 RDI: ffffffff89520108
RBP: ffffffff89407c10 R08: ffffffff89476ec0 R09: 000
Lost 30 message(s)!
Kernel Offset: disabled
Rebooting in 86400 seconds..