======================================
| [ 1293.329639][   T71]
| [ 1293.334450][   T71] ------------[ cut here ]------------
| [ 1293.334965][ T71] WARNING: CPU: 0 PID: 71 at lib/ref_tracker.c:179 ref_tracker_dir_exit (lib/ref_tracker.c:179) 
| [ 1293.335699][   T71] Modules linked in: geneve vxlan ip6_udp_tunnel udp_tunnel [last unloaded: netdevsim]
[ 1293.337009][   T71] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[ 1293.337869][   T71] Workqueue: netns cleanup_net
[ 1293.338270][ T71] RIP: 0010:ref_tracker_dir_exit (lib/ref_tracker.c:179) 
[ 1293.338722][ T71] Code: 38 00 0f 85 58 02 00 00 49 8b 04 24 4d 89 e6 4c 39 e5 0f 85 2a ff ff ff 48 8b 1c 24 48 8b 74 24 10 48 89 df e8 a9 11 88 01 90 <0f> 0b 90 48 8d 6b 4c be 04 00 00 00 48 89 ef e8 94 c2 95 ff 48 89
All code
========
   0:	38 00                	cmp    %al,(%rax)
   2:	0f 85 58 02 00 00    	jne    0x260
   8:	49 8b 04 24          	mov    (%r12),%rax
   c:	4d 89 e6             	mov    %r12,%r14
   f:	4c 39 e5             	cmp    %r12,%rbp
  12:	0f 85 2a ff ff ff    	jne    0xffffffffffffff42
  18:	48 8b 1c 24          	mov    (%rsp),%rbx
  1c:	48 8b 74 24 10       	mov    0x10(%rsp),%rsi
  21:	48 89 df             	mov    %rbx,%rdi
  24:	e8 a9 11 88 01       	call   0x18811d2
  29:	90                   	nop
  2a:*	0f 0b                	ud2		<-- trapping instruction
  2c:	90                   	nop
  2d:	48 8d 6b 4c          	lea    0x4c(%rbx),%rbp
  31:	be 04 00 00 00       	mov    $0x4,%esi
  36:	48 89 ef             	mov    %rbp,%rdi
  39:	e8 94 c2 95 ff       	call   0xffffffffff95c2d2
  3e:	48                   	rex.W
  3f:	89                   	.byte 0x89

Code starting with the faulting instruction
===========================================
   0:	0f 0b                	ud2
   2:	90                   	nop
   3:	48 8d 6b 4c          	lea    0x4c(%rbx),%rbp
   7:	be 04 00 00 00       	mov    $0x4,%esi
   c:	48 89 ef             	mov    %rbp,%rdi
   f:	e8 94 c2 95 ff       	call   0xffffffffff95c2a8
  14:	48                   	rex.W
  15:	89                   	.byte 0x89
[ 1293.340061][   T71] RSP: 0018:ffffc9000051fb60 EFLAGS: 00010286
[ 1293.340538][   T71] RAX: 0000000000000002 RBX: ffff888007ea9978 RCX: 1ffffffff2ad157d
[ 1293.341050][   T71] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff92267ef1
[ 1293.341577][   T71] RBP: ffff888007ea99d0 R08: 0000000000000001 R09: fffffbfff2ac9687
[ 1293.342100][   T71] R10: ffffffff9564b43f R11: ffffc9000051f7a1 R12: ffff888007ea99d0
[ 1293.342608][   T71] R13: dead000000000100 R14: ffff888007ea99d0 R15: dffffc0000000000
[ 1293.343088][   T71] FS:  0000000000000000(0000) GS:ffff888035200000(0000) knlGS:0000000000000000
[ 1293.343550][   T71] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 1293.343887][   T71] CR2: 00007f5e0b0a9a30 CR3: 0000000012320004 CR4: 0000000000770ef0
[ 1293.344345][   T71] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 1293.344782][   T71] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 1293.345196][   T71] PKRU: 55555554
[ 1293.345422][   T71] Call Trace:
[ 1293.345633][   T71]  <TASK>
[ 1293.345843][ T71] ? __warn (kernel/panic.c:677) 
[ 1293.346107][ T71] ? ref_tracker_dir_exit (lib/ref_tracker.c:179) 
[ 1293.346405][ T71] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[ 1293.346731][ T71] ? handle_bug (arch/x86/kernel/traps.c:238) 
[ 1293.347032][ T71] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[ 1293.347378][ T71] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[ 1293.347748][ T71] ? _raw_spin_unlock_irqrestore (./include/linux/spinlock_api_smp.h:151 kernel/locking/spinlock.c:194) 
[ 1293.348174][ T71] ? ref_tracker_dir_exit (lib/ref_tracker.c:179) 
[ 1293.348566][ T71] ? __pfx_ref_tracker_dir_exit (lib/ref_tracker.c:158) 
[ 1293.348968][ T71] ? kfree (mm/slub.c:4299 mm/slub.c:4409) 
[ 1293.349273][ T71] net_free (net/core/net_namespace.c:464 net/core/net_namespace.c:456) 
[ 1293.349557][ T71] cleanup_net (net/core/net_namespace.c:651) 
[ 1293.349874][ T71] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5719) 
[ 1293.350287][ T71] ? __pfx_cleanup_net (net/core/net_namespace.c:581) 
[ 1293.350644][ T71] ? lock_acquire (./include/trace/events/lock.h:24 kernel/locking/lockdep.c:5725) 
[ 1293.350968][ T71] ? process_one_work (kernel/workqueue.c:2609) 
[ 1293.351350][ T71] process_one_work (kernel/workqueue.c:2633) 
[ 1293.351775][ T71] ? hlock_class (./arch/x86/include/asm/bitops.h:227 ./arch/x86/include/asm/bitops.h:239 ./include/asm-generic/bitops/instrumented-non-atomic.h:142 kernel/locking/lockdep.c:228) 
[ 1293.352100][ T71] ? __pfx_process_one_work (kernel/workqueue.c:2542) 
[ 1293.352553][ T71] ? assign_work (kernel/workqueue.c:1101) 
[ 1293.352931][ T71] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[ 1293.353321][ T71] ? lockdep_hardirqs_on_prepare.part.0 (kernel/locking/lockdep.c:4300 kernel/locking/lockdep.c:4359) 
[ 1293.353809][ T71] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[ 1293.354230][ T71] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[ 1293.354587][ T71] kthread (kernel/kthread.c:388) 
make: Leaving di[ 1293.354876][ T71] ? __pfx_kthread (kernel/kthread.c:341) 
rectory '/home/v[ 1293.355299][ T71] ret_from_fork (arch/x86/kernel/process.c:147) 
irtme/testing-14[ 1293.355661][ T71] ? __pfx_kthread (kernel/kthread.c:341) 


Finger prints:
ref_tracker_dir_exit:net_free:cleanup_net:process_one_work