======================================
| [    6.899131] #PF: supervisor write access in kernel mode
| [    6.899188] #PF: error_code(0x0002) - not-present page
| [    6.899238] PGD 0 P4D 0
| [    6.899267] Oops: Oops: 0002 [#1] SMP
[    6.899392] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[    6.899456] Workqueue: netns cleanup_net
[    6.899498] RIP: 0010:work_grab_pending (./arch/x86/include/asm/bitops.h:136 ./include/asm-generic/bitops/instrumented-atomic.h:72 kernel/workqueue.c:2072 kernel/workqueue.c:2160)
[    6.899551] Code: 83 e6 01 41 57 41 56 4c 8d 77 20 41 55 41 54 41 89 f4 55 48 89 d5 53 48 89 fb 9c 58 fa 48 89 45 00 45 85 e4 0f 85 8a 00 00 00 <f0> 48 0f ba 2b 00 41 0f 92 c5 72 0e 5b 44 89 e8 5d 41 5c 41 5d 41
All code
========
   0:	83 e6 01             	and    $0x1,%esi
   3:	41 57                	push   %r15
   5:	41 56                	push   %r14
   7:	4c 8d 77 20          	lea    0x20(%rdi),%r14
   b:	41 55                	push   %r13
   d:	41 54                	push   %r12
   f:	41 89 f4             	mov    %esi,%r12d
  12:	55                   	push   %rbp
  13:	48 89 d5             	mov    %rdx,%rbp
  16:	53                   	push   %rbx
  17:	48 89 fb             	mov    %rdi,%rbx
  1a:	9c                   	pushf
  1b:	58                   	pop    %rax
  1c:	fa                   	cli
  1d:	48 89 45 00          	mov    %rax,0x0(%rbp)
  21:	45 85 e4             	test   %r12d,%r12d
  24:	0f 85 8a 00 00 00    	jne    0xb4
  2a:*	f0 48 0f ba 2b 00    	lock btsq $0x0,(%rbx)		<-- trapping instruction
  30:	41 0f 92 c5          	setb   %r13b
  34:	72 0e                	jb     0x44
  36:	5b                   	pop    %rbx
  37:	44 89 e8             	mov    %r13d,%eax
  3a:	5d                   	pop    %rbp
  3b:	41 5c                	pop    %r12
  3d:	41 5d                	pop    %r13
  3f:	41                   	rex.B

Code starting with the faulting instruction
===========================================
   0:	f0 48 0f ba 2b 00    	lock btsq $0x0,(%rbx)
   6:	41 0f 92 c5          	setb   %r13b
   a:	72 0e                	jb     0x1a
   c:	5b                   	pop    %rbx
   d:	44 89 e8             	mov    %r13d,%eax
  10:	5d                   	pop    %rbp
  11:	41 5c                	pop    %r12
  13:	41 5d                	pop    %r13
  15:	41                   	rex.B
[    6.899721] RSP: 0018:ffffbfb14025fbb8 EFLAGS: 00010046
[    6.899778] RAX: 0000000000000246 RBX: 0000000000000000 RCX: 00000000ffffffff
[    6.899851] RDX: ffffbfb14025fbf0 RSI: 0000000000000000 RDI: 0000000000000000
[    6.899926] RBP: ffffbfb14025fbf0 R08: ffffffffbae6d160 R09: 0000000000000101
[    6.900000] R10: ffffffffbb6080d8 R11: ffffbfb140003ff8 R12: 0000000000000000
[    6.900071] R13: ffffbfb14025fce8 R14: 0000000000000020 R15: ffffbfb14025fdf0
[    6.900146] FS:  0000000000000000(0000) GS:ffff9d77c2dd8000(0000) knlGS:0000000000000000
[    6.900224] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    6.900292] CR2: 0000000000000000 CR3: 0000000003bbc001 CR4: 0000000000772ef0
[    6.900367] PKRU: 55555554
[    6.900397] Call Trace:
[    6.900423]  <TASK>
[    6.900454]  __cancel_work (kernel/workqueue.c:4366)
[    6.900494]  ? dev_deactivate_many (net/sched/sch_generic.c:1324 net/sched/sch_generic.c:1382)
[    6.900551]  __cancel_work_sync (kernel/workqueue.c:4381)
[    6.900587]  __dev_close_many (net/core/dev.c:1879 (discriminator 2) net/core/dev.c:1932 (discriminator 2))
[    6.900629]  netif_close_many (net/core/dev.c:1959)
[    6.900667]  unregister_netdevice_many_notify (net/core/dev.c:12545)
[    6.900723]  default_device_exit_batch (net/core/dev.c:13229)
[    6.900776]  ops_undo_list (net/core/net_namespace.c:251)
[    6.900817]  cleanup_net (net/core/net_namespace.c:698)
[    6.900852]  process_one_work (kernel/workqueue.c:3268)
[    6.900888]  worker_thread (kernel/workqueue.c:3340 kernel/workqueue.c:3427)
[    6.900925]  ? rescuer_thread (kernel/workqueue.c:3373)
[    6.900963]  kthread (kernel/kthread.c:463)
[    6.900999]  ? kthreads_online_cpu (kernel/kthread.c:412)
[    6.901053]  ? kthreads_online_cpu (kernel/kthread.c:412)
[    6.901102]  ret_from_fork (arch/x86/kernel/process.c:164)
[    6.901146]  ? kthreads_online_cpu (kernel/kthread.c:412)


Finger prints:
work_grab_pending:__cancel_work:__cancel_work_sync:__dev_close_many:netif_close_many