======================================
| [ 1215.793445][   T11] br0: port 1(vxlan0) entered disabled state
| [ 1215.838362][   T11] ------------[ cut here ]------------
| [ 1215.839302][ T11] WARNING: CPU: 3 PID: 11 at net/core/dev.c:11120 unregister_netdevice_many_notify (net/core/dev.c:11120 (discriminator 1)) 
| [ 1215.839996][   T11] Modules linked in: vxlan act_mirred act_tunnel_key bareudp mpls_iptunnel mpls_router xt_conntrack nf_conntrack nf_defrag_ipv4 nft_compat nf_tables nf_defrag_ipv6 xfrm_interface sha1_generic xfrm_user sctp_diag sctp ip6_udp_tunnel udp_tunnel libcrc32c drop_monitor act_gact cls_flower sch_ingress netdevsim psample
[ 1215.842149][   T11] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[ 1215.842854][   T11] Workqueue: netns cleanup_net
[ 1215.843108][ T11] RIP: 0010:unregister_netdevice_many_notify (net/core/dev.c:11120 (discriminator 1)) 
[ 1215.843479][ T11] Code: 05 64 56 61 02 01 90 ba 32 1b 00 00 48 c7 c6 a0 9a 33 9c 48 c7 c7 00 9c 33 9c e8 bf 59 08 fe 90 0f 0b 90 90 e9 8a fb ff ff 90 <0f> 0b 90 e9 aa fb ff ff e8 c7 5c 27 fe e9 37 fc ff ff 90 0f 0b 0f
All code
========
   0:	05 64 56 61 02       	add    $0x2615664,%eax
   5:	01 90 ba 32 1b 00    	add    %edx,0x1b32ba(%rax)
   b:	00 48 c7             	add    %cl,-0x39(%rax)
   e:	c6                   	(bad)
   f:	a0 9a 33 9c 48 c7 c7 	movabs 0x9c00c7c7489c339a,%al
  16:	00 9c 
  18:	33 9c e8 bf 59 08 fe 	xor    -0x1f7a641(%rax,%rbp,8),%ebx
  1f:	90                   	nop
  20:	0f 0b                	ud2
  22:	90                   	nop
  23:	90                   	nop
  24:	e9 8a fb ff ff       	jmp    0xfffffffffffffbb3
  29:	90                   	nop
  2a:*	0f 0b                	ud2		<-- trapping instruction
  2c:	90                   	nop
  2d:	e9 aa fb ff ff       	jmp    0xfffffffffffffbdc
  32:	e8 c7 5c 27 fe       	call   0xfffffffffe275cfe
  37:	e9 37 fc ff ff       	jmp    0xfffffffffffffc73
  3c:	90                   	nop
  3d:	0f 0b                	ud2
  3f:	0f                   	.byte 0xf

Code starting with the faulting instruction
===========================================
   0:	0f 0b                	ud2
   2:	90                   	nop
   3:	e9 aa fb ff ff       	jmp    0xfffffffffffffbb2
   8:	e8 c7 5c 27 fe       	call   0xfffffffffe275cd4
   d:	e9 37 fc ff ff       	jmp    0xfffffffffffffc49
  12:	90                   	nop
  13:	0f 0b                	ud2
  15:	0f                   	.byte 0xf
[ 1215.844530][   T11] RSP: 0018:ffffc900000bfb28 EFLAGS: 00010212
[ 1215.844937][   T11] RAX: ffff8880023ea418 RBX: ffff888010700000 RCX: ffffffff992c7967
[ 1215.845342][   T11] RDX: 1ffffffff3aaff44 RSI: 0000000000000008 RDI: ffffffff9d57fa20
[ 1215.845822][   T11] RBP: ffff8880107001c0 R08: 0000000000000000 R09: fffffbfff3aaff44
[ 1215.846232][   T11] R10: ffffffff9d57fa27 R11: ffffc900000bf621 R12: ffff88800677c2c0
[ 1215.846700][   T11] R13: ffffc900000bfc00 R14: dffffc0000000000 R15: ffff88800677c2c0
[ 1215.847157][   T11] FS:  0000000000000000(0000) GS:ffff888035e00000(0000) knlGS:0000000000000000
[ 1215.847691][   T11] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 1215.848044][   T11] CR2: 000055f8e20e3dec CR3: 000000000cd34002 CR4: 0000000000770ef0
[ 1215.848476][   T11] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 1215.848991][   T11] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 1215.849412][   T11] PKRU: 55555554
[ 1215.849639][   T11] Call Trace:
[ 1215.849813][   T11]  <TASK>
[ 1215.850016][ T11] ? __warn (kernel/panic.c:677) 
[ 1215.850239][ T11] ? unregister_netdevice_many_notify (net/core/dev.c:11120 (discriminator 1)) 
[ 1215.850625][ T11] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[ 1215.850875][ T11] ? handle_bug (arch/x86/kernel/traps.c:238) 
[ 1215.851123][ T11] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[ 1215.851410][ T11] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[ 1215.851734][ T11] ? mutex_is_locked (./arch/x86/include/asm/atomic64_64.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2569 ./include/linux/atomic/atomic-long.h:38 ./include/linux/atomic/atomic-instrumented.h:3161 kernel/locking/mutex.c:81 kernel/locking/mutex.c:91) 
[ 1215.852000][ T11] ? unregister_netdevice_many_notify (net/core/dev.c:11120 (discriminator 1)) 
[ 1215.852360][ T11] ? unregister_netdevice_many_notify (net/core/dev.c:6962 net/core/dev.c:11120) 
[ 1215.852766][ T11] ? __pfx_unregister_netdevice_many_notify (net/core/dev.c:11035) 
[ 1215.853156][ T11] ? mutex_is_locked (./arch/x86/include/asm/atomic64_64.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2569 ./include/linux/atomic/atomic-long.h:38 ./include/linux/atomic/atomic-instrumented.h:3161 kernel/locking/mutex.c:81 kernel/locking/mutex.c:91) 
[ 1215.853418][ T11] ? nexthop_net_exit_batch_rtnl (net/ipv4/nexthop.c:569 net/ipv4/nexthop.c:1918 net/ipv4/nexthop.c:2426 net/ipv4/nexthop.c:3754) 
[ 1215.853780][ T11] cleanup_net (net/core/net_namespace.c:633) 
[ 1215.854054][ T11] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5719) 
[ 1215.854385][ T11] ? __pfx_cleanup_net (net/core/net_namespace.c:581) 
[ 1215.854676][ T11] ? lock_acquire (./include/trace/events/lock.h:24 kernel/locking/lockdep.c:5725) 
[ 1215.854965][ T11] ? process_one_work (kernel/workqueue.c:2609) 
[ 1215.855282][ T11] process_one_work (kernel/workqueue.c:2633) 
[ 1215.855562][ T11] ? 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) 
[ 1215.855816][ T11] ? __pfx_process_one_work (kernel/workqueue.c:2542) 
[ 1215.856131][ T11] ? assign_work (kernel/workqueue.c:1101) 
[ 1215.856405][ T11] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[ 1215.856710][ T11] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[ 1215.857029][ T11] kthread (kernel/kthread.c:388) 
[ 1215.857270][ T11] ? __pfx_kthread (kernel/kthread.c:341) 
[ 1215.857516][ T11] ret_from_fork (arch/x86/kernel/process.c:147) 
[ 1215.857786][ T11] ? __pfx_kthread (kernel/kthread.c:341) 


Finger prints:
unregister_netdevice_many_notify:cleanup_net:process_one_work:worker_thread