======================================
| [ 3635.630702] ------------[ cut here ]------------
| [ 3635.631301] DEBUG_LOCKS_WARN_ON(lock->magic != lock)
| [ 3635.631326] WARNING: CPU: 2 PID: 11 at kernel/locking/mutex.c:587 __mutex_lock (kernel/locking/mutex.c:587 kernel/locking/mutex.c:752) 
| [ 3635.632971] Modules linked in: act_gact xt_HL amt l2tp_ip6 l2tp_eth l2tp_ip l2tp_netlink l2tp_core sch_etf sch_fq act_tunnel_key bareudp mpls_iptunnel mpls_router xfrm_interface sha1_generic xfrm_user act_mirred cls_matchall ip6_gre gre vxlan xt_length act_ct nf_flow_table cls_flower cls_bpf sch_ingress xt_conntrack sctp_diag sctp nft_chain_nat xt_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip6t_REJECT ipt_REJECT nft_compat nf_tables libcrc32c [last unloaded: test_bpf]
[ 3635.638313] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[ 3635.639264] Workqueue: netns cleanup_net
[ 3635.639550] RIP: 0010:__mutex_lock (kernel/locking/mutex.c:587 kernel/locking/mutex.c:752) 
[ 3635.640039] Code: ff 90 e8 a2 e7 70 ff 85 c0 74 23 8b 35 9c 8e db 00 85 f6 75 19 90 48 c7 c6 97 37 aa b7 48 c7 c7 3a ac a9 b7 e8 00 04 26 ff 90 <0f> 0b 90 90 90 e9 03 fd ff ff 4c 8d 6d a0 4c 89 e7 4c 89 ee e8 d6
All code
========
   0:	ff 90 e8 a2 e7 70    	call   *0x70e7a2e8(%rax)
   6:	ff 85 c0 74 23 8b    	incl   -0x74dc8b40(%rbp)
   c:	35 9c 8e db 00       	xor    $0xdb8e9c,%eax
  11:	85 f6                	test   %esi,%esi
  13:	75 19                	jne    0x2e
  15:	90                   	nop
  16:	48 c7 c6 97 37 aa b7 	mov    $0xffffffffb7aa3797,%rsi
  1d:	48 c7 c7 3a ac a9 b7 	mov    $0xffffffffb7a9ac3a,%rdi
  24:	e8 00 04 26 ff       	call   0xffffffffff260429
  29:	90                   	nop
  2a:*	0f 0b                	ud2		<-- trapping instruction
  2c:	90                   	nop
  2d:	90                   	nop
  2e:	90                   	nop
  2f:	e9 03 fd ff ff       	jmp    0xfffffffffffffd37
  34:	4c 8d 6d a0          	lea    -0x60(%rbp),%r13
  38:	4c 89 e7             	mov    %r12,%rdi
  3b:	4c 89 ee             	mov    %r13,%rsi
  3e:	e8                   	.byte 0xe8
  3f:	d6                   	(bad)

Code starting with the faulting instruction
===========================================
   0:	0f 0b                	ud2
   2:	90                   	nop
   3:	90                   	nop
   4:	90                   	nop
   5:	e9 03 fd ff ff       	jmp    0xfffffffffffffd0d
   a:	4c 8d 6d a0          	lea    -0x60(%rbp),%r13
   e:	4c 89 e7             	mov    %r12,%rdi
  11:	4c 89 ee             	mov    %r13,%rsi
  14:	e8                   	.byte 0xe8
  15:	d6                   	(bad)
[ 3635.641523] RSP: 0018:ffffa5ba00063ab0 EFLAGS: 00010286
[ 3635.642038] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00000000ffffdfff
[ 3635.642614] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001
[ 3635.643315] RBP: ffffa5ba00063b30 R08: ffffffffb7f78508 R09: 00000000ffffdfff
[ 3635.643999] R10: ffffffffb7e98520 R11: ffffffffb7f535f0 R12: ffff9687047cf700
[ 3635.644912] R13: 0000000000000000 R14: 0000000000000000 R15: ffff968705b8bc00
[ 3635.645768] FS:  0000000000000000(0000) GS:ffff96873ed00000(0000) knlGS:0000000000000000
[ 3635.646768] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 3635.647479] CR2: 00007f408c41b000 CR3: 0000000011a60006 CR4: 0000000000770ef0
[ 3635.648345] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 3635.649216] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 3635.650056] PKRU: 55555554
[ 3635.650361] Call Trace:
[ 3635.650653]  <TASK>
[ 3635.650831] ? __warn (kernel/panic.c:677) 
[ 3635.651128] ? __mutex_lock (kernel/locking/mutex.c:587 kernel/locking/mutex.c:752) 
[ 3635.651340] ? report_bug (lib/bug.c:201 lib/bug.c:219) 
[ 3635.651545] ? handle_bug (arch/x86/kernel/traps.c:238) 
[ 3635.651745] ? exc_invalid_op (arch/x86/kernel/traps.c:259 (discriminator 1)) 
[ 3635.651956] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:568) 
[ 3635.652298] ? __mutex_lock (kernel/locking/mutex.c:587 kernel/locking/mutex.c:752) 
[ 3635.652782] ? refcount_dec_and_mutex_lock (./arch/x86/include/asm/atomic.h:103 ./include/linux/atomic/atomic-arch-fallback.h:949 ./include/linux/atomic/atomic-instrumented.h:401 ./include/linux/refcount.h:261 ./include/linux/refcount.h:304 ./include/linux/refcount.h:322 lib/refcount.c:119 lib/refcount.c:113) 
[ 3635.653127] ? up_read (kernel/locking/rwsem.c:1622) 
[ 3635.653476] ? tc_setup_cb_destroy (net/sched/cls_api.c:3715) 
[ 3635.654042] ? refcount_dec_and_mutex_lock (./arch/x86/include/asm/atomic.h:103 ./include/linux/atomic/atomic-arch-fallback.h:949 ./include/linux/atomic/atomic-instrumented.h:401 ./include/linux/refcount.h:261 ./include/linux/refcount.h:304 ./include/linux/refcount.h:322 lib/refcount.c:119 lib/refcount.c:113) 
[ 3635.654764] refcount_dec_and_mutex_lock (./arch/x86/include/asm/atomic.h:103 ./include/linux/atomic/atomic-arch-fallback.h:949 ./include/linux/atomic/atomic-instrumented.h:401 ./include/linux/refcount.h:261 ./include/linux/refcount.h:304 ./include/linux/refcount.h:322 lib/refcount.c:119 lib/refcount.c:113) 
[ 3635.655380] __tcf_action_put (net/sched/act_api.c:377) 
[ 3635.655936] tcf_action_destroy (net/sched/act_api.c:413 net/sched/act_api.c:393 net/sched/act_api.c:1175) 
[ 3635.656530] tcf_exts_destroy (net/sched/cls_api.c:3312) 
[ 3635.657092] __fl_destroy_filter (./include/net/pkt_cls.h:261 net/sched/cls_flower.c:425) cls_flower
[ 3635.657854] __fl_delete (net/sched/cls_flower.c:574) cls_flower
[ 3635.658562] fl_destroy (net/sched/cls_flower.c:599) cls_flower
[ 3635.659115] tcf_proto_destroy (net/sched/cls_api.c:418) 
[ 3635.659586] tcf_chain_flush (net/sched/cls_api.c:737) 
[ 3635.660083] __tcf_block_put (net/sched/cls_api.c:1070 net/sched/cls_api.c:1141 net/sched/cls_api.c:1305) 
[ 3635.660550] clsact_destroy (net/sched/sch_ingress.c:302) sch_ingress
[ 3635.661132] __qdisc_destroy (net/sched/sch_generic.c:1067) 
[ 3635.661593] dev_shutdown (net/sched/sch_generic.c:1482) 
[ 3635.661979] unregister_netdevice_many_notify (./include/net/tcx.h:168 net/core/dev.c:11084) 
[ 3635.662374] cleanup_net (net/core/net_namespace.c:633) 
[ 3635.662696] ? process_one_work (kernel/workqueue.c:2606) 
[ 3635.663006] process_one_work (kernel/workqueue.c:2633) 
[ 3635.663408] worker_thread (kernel/workqueue.c:2700 kernel/workqueue.c:2787) 
[ 3635.663636] ? __pfx_worker_thread (kernel/workqueue.c:2733) 
[ 3635.663921] kthread (kernel/kthread.c:388) 
[ 3635.664207] ? __pfx_kthread (kernel/kthread.c:341) 
[ 3635.664428] ret_from_fork (arch/x86/kernel/process.c:147) 
[ 3635.664657] ? __pfx_kthread (kernel/kthread.c:341) 


Finger prints:
__mutex_lock:refcount_dec_and_mutex_lock:__tcf_action_put:tcf_action_destroy