======================================
| [  803.695305][ T3942]  #2: ff110000122ca100 (&dev->mutex){....}-{4:4}, at: nfc_dev_down (net/nfc/core.c:145)
| [  803.695483][ T3942]  #3: ff11000012df4350 (&ndev->req_lock){+.+.}-{4:4}, at: nci_close_device.isra.0 (./include/linux/instrumented.h:112 ./include/asm-generic/bitops/instrumented-atomic.h:85 net/nfc/nci/core.c:563)
| [  803.695681][ T3942]
| [  803.695681][ T3942] stack backtrace:
[  803.695811][ T3942] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  803.695813][ T3942] Call Trace:
[  803.695814][ T3942]  <TASK>
[  803.695816][ T3942]  dump_stack_lvl (lib/dump_stack.c:122)
[  803.695820][ T3942]  print_circular_bug.cold (kernel/locking/lockdep.c:2046)
[  803.695823][ T3942]  check_noncircular (kernel/locking/lockdep.c:2175)
[  803.695826][ T3942]  check_prev_add (kernel/locking/lockdep.c:3166 (discriminator 4))
[  803.695828][ T3942]  ? find_held_lock (kernel/locking/lockdep.c:5350 (discriminator 1))
[  803.695830][ T3942]  validate_chain (kernel/locking/lockdep.c:3285 kernel/locking/lockdep.c:3908)
[  803.695832][ T3942]  ? rcu_read_lock_any_held (kernel/rcu/update.c:386 (discriminator 1) kernel/rcu/update.c:380 (discriminator 1))
[  803.695835][ T3942]  __lock_acquire (kernel/locking/lockdep.c:5237 (discriminator 1))
[  803.695837][ T3942]  lock_acquire.part.0 (kernel/locking/lockdep.c:470 kernel/locking/lockdep.c:5870)
[  803.695839][ T3942]  ? touch_wq_lockdep_map (kernel/workqueue.c:3990 (discriminator 1))
[  803.695841][ T3942]  ? rcu_is_watching (./include/linux/context_tracking.h:128 (discriminator 1) kernel/rcu/tree.c:752 (discriminator 1))
[  803.695843][ T3942]  ? lock_acquire.part.0 (kernel/locking/lockdep.c:470 kernel/locking/lockdep.c:5870)
[  803.695845][ T3942]  ? lock_acquire (./include/trace/events/lock.h:24 (discriminator 33) kernel/locking/lockdep.c:5831 (discriminator 33))
[  803.695847][ T3942]  ? touch_wq_lockdep_map (kernel/workqueue.c:3990 (discriminator 1))
[  803.695849][ T3942]  touch_wq_lockdep_map (kernel/workqueue.c:3991 (discriminator 1))
[  803.695851][ T3942]  ? touch_wq_lockdep_map (kernel/workqueue.c:3990 (discriminator 1))
[  803.695853][ T3942]  __flush_workqueue (kernel/workqueue.c:4034)
[  803.695855][ T3942]  ? __mutex_lock (kernel/locking/mutex.c:624 (discriminator 3) kernel/locking/mutex.c:776 (discriminator 3))
[  803.695857][ T3942]  ? lockdep_hardirqs_on (kernel/locking/lockdep.c:4473)
[  803.695860][ T3942]  ? __mutex_lock (kernel/locking/mutex.c:624 (discriminator 3) kernel/locking/mutex.c:776 (discriminator 3))
[  803.695861][ T3942]  ? nci_close_device.isra.0 (./include/linux/instrumented.h:112 ./include/asm-generic/bitops/instrumented-atomic.h:85 net/nfc/nci/core.c:563)
[  803.695864][ T3942]  ? idle_cull_fn (kernel/workqueue.c:4021)
[  803.695868][ T3942]  nci_close_device.isra.0 (net/nfc/nci/core.c:584)
[  803.695870][ T3942]  nci_dev_down (net/nfc/nci/core.c:649)
[  803.695872][ T3942]  nfc_dev_down (net/nfc/core.c:163)
[  803.695874][ T3942]  nfc_genl_dev_down (net/nfc/nfc.h:103 net/nfc/netlink.c:798)
[  803.695876][ T3942]  genl_family_rcv_msg_doit (net/netlink/genetlink.c:1116)
[  803.695878][ T3942]  ? genl_family_rcv_msg_attrs_parse.isra.0 (net/netlink/genetlink.c:1087)
[  803.695880][ T3942]  ? lock_acquire (./include/trace/events/lock.h:24 (discriminator 33) kernel/locking/lockdep.c:5831 (discriminator 33))
[  803.695883][ T3942]  ? rcu_is_watching (./include/linux/context_tracking.h:128 (discriminator 1) kernel/rcu/tree.c:752 (discriminator 1))
[  803.695885][ T3942]  ? cap_capable (./include/trace/events/capability.h:26 (discriminator 33) security/commoncap.c:130 (discriminator 33))
[  803.695889][ T3942]  genl_family_rcv_msg (net/netlink/genetlink.c:1194)
[  803.695891][ T3942]  ? genl_family_rcv_msg_dumpit (net/netlink/genetlink.c:1159)
[  803.695893][ T3942]  ? nfc_genl_start_poll (net/nfc/netlink.c:782)
[  803.695895][ T3942]  ? __lock_acquire (kernel/locking/lockdep.c:5237 (discriminator 1))
[  803.695898][ T3942]  genl_rcv_msg (net/netlink/genetlink.c:65 net/netlink/genetlink.c:1210)
[  803.695900][ T3942]  netlink_rcv_skb (net/netlink/af_netlink.c:2550)
[  803.695901][ T3942]  ? genl_family_rcv_msg (net/netlink/genetlink.c:1200)
[  803.695903][ T3942]  ? netlink_ack (net/netlink/af_netlink.c:2527)
[  803.695906][ T3942]  ? netlink_deliver_tap (./include/linux/rcupdate.h:322 (discriminator 1) ./include/linux/rcupdate.h:881 (discriminator 1) ./include/net/netns/generic.h:48 (discriminator 1) net/netlink/af_netlink.c:333 (discriminator 1))
[  803.695908][ T3942]  ? netlink_deliver_tap (./include/linux/rcupdate.h:322 (discriminator 1) ./include/linux/rcupdate.h:881 (discriminator 1) net/netlink/af_netlink.c:340 (discriminator 1))
[  803.695910][ T3942]  genl_rcv (net/netlink/genetlink.c:1219)
[  803.695912][ T3942]  netlink_unicast (net/netlink/af_netlink.c:1319 net/netlink/af_netlink.c:1344)
[  803.695914][ T3942]  ? netlink_attachskb (net/netlink/af_netlink.c:1329)
[  803.695916][ T3942]  ? __alloc_skb (./include/linux/bottom_half.h:20 (discriminator 1) net/core/skbuff.c:695 (discriminator 1))
[  803.695919][ T3942]  ? napi_skb_cache_get (net/core/skbuff.c:674)
[  803.695922][ T3942]  ? __lock_acquire (kernel/locking/lockdep.c:5237 (discriminator 1))
[  803.695925][ T3942]  netlink_sendmsg (net/netlink/af_netlink.c:1894)
[  803.695928][ T3942]  ? netlink_unicast (net/netlink/af_netlink.c:1813)
[  803.695930][ T3942]  ? __might_fault (mm/memory.c:7217 (discriminator 4))
[  803.695934][ T3942]  ? __might_fault (mm/memory.c:7217 (discriminator 4))
[  803.695936][ T3942]  __sys_sendto (net/socket.c:730 (discriminator 1) net/socket.c:742 (discriminator 1) net/socket.c:2205 (discriminator 1))
[  803.695938][ T3942]  ? __ia32_sys_getpeername (net/socket.c:2172)
[  803.695941][ T3942]  ? __lock_release.isra.0 (kernel/locking/lockdep.c:5536)
[  803.695943][ T3942]  ? __rwlock_init (kernel/locking/spinlock_debug.c:114)
[  803.695946][ T3942]  ? set_compat_user_sigmask (kernel/signal.c:3316)
[  803.695949][ T3942]  __x64_sys_sendto (net/socket.c:2212 (discriminator 1) net/socket.c:2208 (discriminator 1) net/socket.c:2208 (discriminator 1))
[  803.695951][ T3942]  ? trace_irq_enable.constprop.0 (./include/trace/events/preemptirq.h:40 (discriminator 33))
[  803.695954][ T3942]  ? lockdep_hardirqs_on (kernel/locking/lockdep.c:4473)
[  803.695956][ T3942]  ? do_syscall_64 (./arch/x86/include/asm/irqflags.h:42 ./arch/x86/include/asm/irqflags.h:119 ./include/linux/entry-common.h:186 arch/x86/entry/syscall_64.c:90)
[  803.695958][ T3942]  do_syscall_64 (arch/x86/entry/syscall_64.c:63 (discriminator 1) arch/x86/entry/syscall_64.c:94 (discriminator 1))
[  803.695959][ T3942]  ? exc_page_fault (arch/x86/mm/fault.c:1480 (discriminator 3) arch/x86/mm/fault.c:1527 (discriminator 3))
[  803.695961][ T3942]  entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
[  803.695963][ T3942] RIP: 0033:0x7fc2ceab19a2
[  803.695966][ T3942] Code: 08 0f 85 01 42 ff ff 49 89 fb 48 89 f0 48 89 d7 48 89 ce 4c 89 c2 4d 89 ca 4c 8b 44 24 08 4c 8b 4c 24 10 4c 89 5c 24 08 0f 05 <c3> 66 2e 0f 1f 84 00 00 00 00 00 66 2e 0f 1f 84 00 00 00 00 00 66
All code
========
   0:	08 0f                	or     %cl,(%rdi)
   2:	85 01                	test   %eax,(%rcx)
   4:	42 ff                	rex.X (bad)
   6:	ff 49 89             	decl   -0x77(%rcx)
   9:	fb                   	sti
   a:	48 89 f0             	mov    %rsi,%rax
   d:	48 89 d7             	mov    %rdx,%rdi
  10:	48 89 ce             	mov    %rcx,%rsi
  13:	4c 89 c2             	mov    %r8,%rdx
  16:	4d 89 ca             	mov    %r9,%r10
  19:	4c 8b 44 24 08       	mov    0x8(%rsp),%r8
  1e:	4c 8b 4c 24 10       	mov    0x10(%rsp),%r9
  23:	4c 89 5c 24 08       	mov    %r11,0x8(%rsp)
  28:	0f 05                	syscall
  2a:*	c3                   	ret		<-- trapping instruction
  2b:	66 2e 0f 1f 84 00 00 	cs nopw 0x0(%rax,%rax,1)
  32:	00 00 00 
  35:	66 2e 0f 1f 84 00 00 	cs nopw 0x0(%rax,%rax,1)
  3c:	00 00 00 
  3f:	66                   	data16

Code starting with the faulting instruction
===========================================
   0:	c3                   	ret
   1:	66 2e 0f 1f 84 00 00 	cs nopw 0x0(%rax,%rax,1)
   8:	00 00 00 
   b:	66 2e 0f 1f 84 00 00 	cs nopw 0x0(%rax,%rax,1)
  12:	00 00 00 
  15:	66                   	data16
[  803.695968][ T3942] RSP: 002b:00007ffc3c520098 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
[  803.695971][ T3942] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fc2ceab19a2
[  803.695972][ T3942] RDX: 000000000000001c RSI: 00007ffc3c520130 RDI: 0000000000000006
[  803.695973][ T3942] RBP: 00007ffc3c5200c0 R08: 00007ffc3c52054c R09: 000000000000000c
[  803.695974][ T3942] R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffc3c520d48


Finger prints:
check_prev_add:validate_chain:__lock_acquire:touch_wq_lockdep_map:__flush_workqueue