======================================
| [ 13.935980][ C2] #4: ffff8880050b3358 (&br->multicast_lock){+.-.}-{3:3}, at: br_multicast_port_query_expired (./include/trace/events/../../../net/bridge/br_private.h:1293 ./include/trace/events/../../../net/bridge/br_private.h:1302 net/bridge/br_multicast.c:1906) bridge 
| [ 13.936494][ C2] #5: ffffffff88b5b5c0 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit (./include/linux/bottom_half.h:20 ./include/linux/rcupdate.h:901 net/core/dev.c:4555) 
| [   13.937027][    C2]
| [   13.937027][    C2] stack backtrace:
[   13.937303][    C2] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   13.937306][    C2] Workqueue: events_unbound linkwatch_event
[   13.937311][    C2] Call Trace:
[   13.937313][    C2]  <IRQ>
[ 13.937316][ C2] dump_stack_lvl (lib/dump_stack.c:123) 
[ 13.937323][ C2] lockdep_rcu_suspicious (kernel/locking/lockdep.c:6848) 
[ 13.937334][ C2] dev_hard_start_xmit (./include/net/net_namespace.h:418 ./include/linux/netdevice.h:2695 net/core/dev.c:2466 net/core/dev.c:3772 net/core/dev.c:3793) 
[ 13.937346][ C2] __dev_queue_xmit (net/core/dev.h:340 net/core/dev.c:4631) 
[ 13.937357][ C2] ? __build_skb_around (./arch/x86/include/asm/atomic.h:28 ./include/linux/atomic/atomic-arch-fallback.h:503 ./include/linux/atomic/atomic-instrumented.h:68 net/core/skbuff.c:381 net/core/skbuff.c:439) 
[ 13.937366][ C2] ? __pfx___dev_queue_xmit (net/core/dev.c:4538) 
[ 13.937369][ C2] ? __pfx___alloc_skb (net/core/skbuff.c:642) 
[ 13.937375][ C2] ? stack_trace_save (kernel/stacktrace.c:114) 
[ 13.937380][ C2] ? __pfx_stack_trace_save (kernel/stacktrace.c:114) 
[ 13.937388][ C2] ? __pfx___br_multicast_query_handle_vlan (net/bridge/br_multicast.c:909) bridge 
[ 13.937443][ C2] br_dev_queue_push_xmit (net/bridge/br_forward.c:34) bridge 
[ 13.937476][ C2] ? __pfx_br_dev_queue_push_xmit (net/bridge/br_forward.c:34) bridge 
[ 13.937512][ C2] ? br_multicast_count (./arch/x86/include/asm/bitops.h:206 ./arch/x86/include/asm/bitops.h:238 ./include/asm-generic/bitops/instrumented-non-atomic.h:142 ./include/trace/events/../../../net/bridge/br_private.h:764 net/bridge/br_multicast.c:5052) bridge 
[ 13.937552][ C2] __br_multicast_send_query (net/bridge/br_multicast.c:1813) bridge 
[ 13.937597][ C2] ? __pfx___br_multicast_send_query (net/bridge/br_multicast.c:1789) bridge 
[ 13.937638][ C2] ? __lock_acquire (kernel/locking/lockdep.c:5228) 
[ 13.937649][ C2] ? br_multicast_send_query (net/bridge/br_multicast.c:1891) bridge 
[ 13.937683][ C2] br_multicast_send_query (net/bridge/br_multicast.c:1891) bridge 
[ 13.937722][ C2] ? __pfx_br_multicast_send_query (net/bridge/br_multicast.c:1852) bridge 
[ 13.937755][ C2] ? br_multicast_port_query_expired (./include/trace/events/../../../net/bridge/br_private.h:1293 ./include/trace/events/../../../net/bridge/br_private.h:1302 net/bridge/br_multicast.c:1906) bridge 
[ 13.937792][ C2] ? __pfx_br_ip4_multicast_port_query_expired (net/bridge/br_multicast.c:1920) bridge 
[ 13.937827][ C2] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5816) 
[ 13.937833][ C2] ? do_raw_spin_lock (./arch/x86/include/asm/atomic.h:107 ./include/linux/atomic/atomic-arch-fallback.h:2170 ./include/linux/atomic/atomic-instrumented.h:1302 ./include/asm-generic/qspinlock.h:111 kernel/locking/spinlock_debug.c:116) 
[ 13.937838][ C2] ? __pfx_do_raw_spin_lock (kernel/locking/spinlock_debug.c:114) 
[ 13.937841][ C2] ? lock_acquire (kernel/locking/lockdep.c:5824) 
[ 13.937844][ C2] ? br_multicast_port_query_expired (./include/trace/events/../../../net/bridge/br_private.h:1293 ./include/trace/events/../../../net/bridge/br_private.h:1302 net/bridge/br_multicast.c:1906) bridge 
[ 13.937885][ C2] ? br_multicast_port_query_expired (net/bridge/br_multicast.c:1917) bridge 
[ 13.937919][ C2] br_multicast_port_query_expired (net/bridge/br_multicast.c:1917) bridge 
[ 13.937955][ C2] ? __pfx_br_ip4_multicast_port_query_expired (net/bridge/br_multicast.c:1920) bridge 
[ 13.937989][ C2] call_timer_fn (kernel/time/timer.c:1789) 
[ 13.937993][ C2] ? call_timer_fn (./include/linux/lockdep.h:31 kernel/time/timer.c:1779) 
[ 13.937996][ C2] ? call_timer_fn (./include/linux/lockdep.h:31 kernel/time/timer.c:1779) 
[ 13.938000][ C2] ? __pfx_call_timer_fn (kernel/time/timer.c:1766) 
[ 13.938004][ C2] ? 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:230) 
[ 13.938013][ C2] ? mark_held_locks (kernel/locking/lockdep.c:4323) 
[ 13.938025][ C2] __run_timers (kernel/time/timer.c:1841 kernel/time/timer.c:2414) 
[ 13.938028][ C2] ? __pfx_br_ip4_multicast_port_query_expired (net/bridge/br_multicast.c:1920) bridge 
[ 13.938071][ C2] ? __pfx___run_timers (kernel/time/timer.c:2385) 
[ 13.938073][ C2] ? clockevents_program_event (kernel/time/clockevents.c:326) 
[ 13.938083][ C2] ? do_raw_spin_lock (./arch/x86/include/asm/atomic.h:107 ./include/linux/atomic/atomic-arch-fallback.h:2170 ./include/linux/atomic/atomic-instrumented.h:1302 ./include/asm-generic/qspinlock.h:111 kernel/locking/spinlock_debug.c:116) 
[ 13.938087][ C2] ? __pfx_do_raw_spin_lock (kernel/locking/spinlock_debug.c:114) 
[ 13.938091][ C2] ? lock_acquire (kernel/locking/lockdep.c:5824) 
[ 13.938094][ C2] ? run_timer_softirq (kernel/time/timer.c:2426 kernel/time/timer.c:2418 kernel/time/timer.c:2435 kernel/time/timer.c:2445) 
[ 13.938105][ C2] run_timer_softirq (kernel/time/timer.c:2427 kernel/time/timer.c:2418 kernel/time/timer.c:2435 kernel/time/timer.c:2445) 
[ 13.938110][ C2] handle_softirqs (kernel/softirq.c:561) 
[ 13.938123][ C2] __irq_exit_rcu (kernel/softirq.c:596 kernel/softirq.c:435 kernel/softirq.c:662) 
[ 13.938126][ C2] irq_exit_rcu (kernel/softirq.c:680) 
[ 13.938129][ C2] sysvec_apic_timer_interrupt (arch/x86/kernel/apic/apic.c:1049 arch/x86/kernel/apic/apic.c:1049) 
[   13.938133][    C2]  </IRQ>
[   13.938134][    C2]  <TASK>
[ 13.938137][ C2] asm_sysvec_apic_timer_interrupt (./arch/x86/include/asm/idtentry.h:702) 
[ 13.938141][ C2] RIP: 0010:_raw_spin_unlock_irqrestore (./include/linux/spinlock_api_smp.h:152 kernel/locking/spinlock.c:194) 
[ 13.938145][ C2] Code: 10 e8 b1 3d 87 fd 48 89 ef e8 f9 ad 87 fd 81 e3 00 02 00 00 75 1d 9c 58 f6 c4 02 75 29 48 85 db 74 01 fb 65 ff 0d b5 0d 4f 78 <74> 0e 5b 5d c3 cc cc cc cc e8 2f df ac fd eb dc 0f 1f 44 00 00 5b
All code
========
   0:	10 e8                	adc    %ch,%al
   2:	b1 3d                	mov    $0x3d,%cl
   4:	87 fd                	xchg   %edi,%ebp
   6:	48 89 ef             	mov    %rbp,%rdi
   9:	e8 f9 ad 87 fd       	call   0xfffffffffd87ae07
   e:	81 e3 00 02 00 00    	and    $0x200,%ebx
  14:	75 1d                	jne    0x33
  16:	9c                   	pushf
  17:	58                   	pop    %rax
  18:	f6 c4 02             	test   $0x2,%ah
  1b:	75 29                	jne    0x46
  1d:	48 85 db             	test   %rbx,%rbx
  20:	74 01                	je     0x23
  22:	fb                   	sti
  23:	65 ff 0d b5 0d 4f 78 	decl   %gs:0x784f0db5(%rip)        # 0x784f0ddf
  2a:*	74 0e                	je     0x3a		<-- trapping instruction
  2c:	5b                   	pop    %rbx
  2d:	5d                   	pop    %rbp
  2e:	c3                   	ret
  2f:	cc                   	int3
  30:	cc                   	int3
  31:	cc                   	int3
  32:	cc                   	int3
  33:	e8 2f df ac fd       	call   0xfffffffffdacdf67
  38:	eb dc                	jmp    0x16
  3a:	0f 1f 44 00 00       	nopl   0x0(%rax,%rax,1)
  3f:	5b                   	pop    %rbx

Code starting with the faulting instruction
===========================================
   0:	74 0e                	je     0x10
   2:	5b                   	pop    %rbx
   3:	5d                   	pop    %rbp
   4:	c3                   	ret
   5:	cc                   	int3
   6:	cc                   	int3
   7:	cc                   	int3
   8:	cc                   	int3
   9:	e8 2f df ac fd       	call   0xfffffffffdacdf3d
   e:	eb dc                	jmp    0xffffffffffffffec
  10:	0f 1f 44 00 00       	nopl   0x0(%rax,%rax,1)
  15:	5b                   	pop    %rbx
[   13.938148][    C2] RSP: 0018:ffffc900002bf7c0 EFLAGS: 00000202
[   13.938151][    C2] RAX: 0000000000000006 RBX: 0000000000000200 RCX: 1ffffffff15866b1
[   13.938153][    C2] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff87b4b761
[   13.938154][    C2] RBP: ffff888002190180 R08: 0000000000000001 R09: fffffbfff1585be1
[   13.938156][    C2] R10: ffffffff8ac2df0f R11: ffff888001d845c0 R12: ffff888002190180
[   13.938158][    C2] R13: ffffea000016c000 R14: ffff8880019759c0 R15: ffff888005b003c0
[ 13.938170][ C2] ? _raw_spin_unlock_irqrestore (./include/linux/spinlock_api_smp.h:151 kernel/locking/spinlock.c:194) 
[ 13.938179][ C2] get_partial_node.part.0 (mm/slub.c:2870) 
[ 13.938194][ C2] ___slab_alloc (mm/slub.c:2831 mm/slub.c:2948 mm/slub.c:3806) 
[ 13.938198][ C2] ? __alloc_skb (net/core/skbuff.c:659) 
[ 13.938202][ C2] ? get_any_partial (./include/linux/seqlock.h:72 ./include/linux/cpuset.h:144 mm/slub.c:2909) 
[ 13.938211][ C2] ? __lock_release (kernel/locking/lockdep.c:5527) 
[ 13.938214][ C2] ? __fib6_clean_all (./include/linux/rcupdate.h:347 ./include/linux/rcupdate.h:880 net/ipv6/ip6_fib.c:2273) 
[ 13.938220][ C2] ? __pfx___lock_release (kernel/locking/lockdep.c:5503) 
[ 13.938222][ C2] ? 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:230) 
[ 13.938231][ C2] ? kmem_cache_alloc_node_noprof (mm/slub.c:3916 mm/slub.c:3991 mm/slub.c:4152 mm/slub.c:4216) 
[ 13.938235][ C2] kmem_cache_alloc_node_noprof (mm/slub.c:3916 mm/slub.c:3991 mm/slub.c:4152 mm/slub.c:4216) 
[ 13.938241][ C2] ? __fib6_clean_all (./include/linux/rcupdate.h:347 ./include/linux/rcupdate.h:880 net/ipv6/ip6_fib.c:2273) 
[ 13.938244][ C2] ? __alloc_skb (net/core/skbuff.c:659) 
[ 13.938251][ C2] __alloc_skb (net/core/skbuff.c:659) 
[ 13.938255][ C2] ? __pfx___alloc_skb (net/core/skbuff.c:642) 
[ 13.938263][ C2] ? rt6_sync_up (net/ipv6/route.c:4797) 
[ 13.938267][ C2] ? __pfx_rt6_sync_up (net/ipv6/route.c:4797) 
[ 13.938275][ C2] inet6_ifinfo_notify (./include/linux/skbuff.h:1339 ./include/net/netlink.h:1019 net/ipv6/addrconf.c:6161) 
[ 13.938282][ C2] addrconf_notify (net/ipv6/addrconf.c:3765 (discriminator 2)) 
[ 13.938291][ C2] notifier_call_chain (kernel/notifier.c:85 (discriminator 2)) 
[ 13.938303][ C2] netdev_state_change (net/core/dev.c:1538 net/core/dev.c:1529) 
[ 13.938307][ C2] ? __pfx_netdev_state_change (net/core/dev.c:1530) 
[ 13.938322][ C2] linkwatch_do_dev (net/core/link_watch.c:186) 
[ 13.938327][ C2] __linkwatch_run_queue (./include/linux/spinlock.h:376 net/core/link_watch.c:245) 
[ 13.938334][ C2] ? __pfx___linkwatch_run_queue (net/core/link_watch.c:195) 
[ 13.938341][ C2] ? lock_acquire (kernel/locking/lockdep.c:5824) 
[ 13.938350][ C2] linkwatch_event (net/core/link_watch.c:287) 
[ 13.938353][ C2] process_one_work (kernel/workqueue.c:3238) 
[ 13.938367][ C2] ? __pfx___lock_release (kernel/locking/lockdep.c:5503) 
[ 13.938372][ C2] ? __pfx_process_one_work (kernel/workqueue.c:3140) 
[ 13.938385][ C2] ? assign_work (kernel/workqueue.c:1200) 
[ 13.938395][ C2] worker_thread (kernel/workqueue.c:3313 kernel/workqueue.c:3400) 
[ 13.938409][ C2] ? __pfx_worker_thread (kernel/workqueue.c:3346) 
[ 13.938415][ C2] kthread (kernel/kthread.c:464) 
[ 13.938420][ C2] ? __pfx_kthread (kernel/kthread.c:413) 
[ 13.938428][ C2] ? __pfx_kthread (kernel/kthread.c:413) 
[ 13.938434][ C2] ret_from_fork (arch/x86/kernel/process.c:148) 
[ 13.938438][ C2] ? __pfx_kthread (kernel/kthread.c:413) 


Finger prints:
lockdep_rcu_suspicious:dev_hard_start_xmit:__dev_queue_xmit:br_dev_queue_push_xmit:__br_multicast_send_query