======================================
| [ 1381.166304][ C3] #4: ffff88800a69b358 (&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 
| [ 1381.166775][ C3] #5: ffffffff9e95b5c0 (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) 
| [ 1381.167116][    C3]
| [ 1381.167116][    C3] stack backtrace:
[ 1381.167365][    C3] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[ 1381.167368][    C3] Workqueue: events_unbound linkwatch_event
[ 1381.167372][    C3] Call Trace:
[ 1381.167375][    C3]  <IRQ>
[ 1381.167378][ C3] dump_stack_lvl (lib/dump_stack.c:123) 
[ 1381.167385][ C3] lockdep_rcu_suspicious (kernel/locking/lockdep.c:6848) 
[ 1381.167395][ C3] 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) 
[ 1381.167406][ C3] __dev_queue_xmit (net/core/dev.h:340 net/core/dev.c:4631) 
[ 1381.167417][ C3] ? __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) 
[ 1381.167427][ C3] ? __pfx___dev_queue_xmit (net/core/dev.c:4538) 
[ 1381.167430][ C3] ? __pfx___alloc_skb (net/core/skbuff.c:642) 
[ 1381.167433][ C3] ? __pfx___lock_release (kernel/locking/lockdep.c:5503) 
[ 1381.167442][ C3] ? __pfx_do_raw_spin_lock (kernel/locking/spinlock_debug.c:114) 
[ 1381.167449][ C3] ? __pfx___br_multicast_query_handle_vlan (net/bridge/br_multicast.c:909) bridge 
[ 1381.167501][ C3] br_dev_queue_push_xmit (net/bridge/br_forward.c:34) bridge 
[ 1381.167531][ C3] ? hlock_class (kernel/locking/lockdep.c:225) 
[ 1381.167536][ C3] ? __pfx_br_dev_queue_push_xmit (net/bridge/br_forward.c:34) bridge 
[ 1381.167568][ C3] ? 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 
[ 1381.167608][ C3] __br_multicast_send_query (net/bridge/br_multicast.c:1813) bridge 
[ 1381.167653][ C3] ? __pfx___br_multicast_send_query (net/bridge/br_multicast.c:1789) bridge 
[ 1381.167694][ C3] ? __lock_acquire (kernel/locking/lockdep.c:5228) 
[ 1381.167704][ C3] ? br_multicast_send_query (net/bridge/br_multicast.c:1891) bridge 
[ 1381.167739][ C3] br_multicast_send_query (net/bridge/br_multicast.c:1891) bridge 
[ 1381.167778][ C3] ? __pfx_br_multicast_send_query (net/bridge/br_multicast.c:1852) bridge 
[ 1381.167812][ C3] ? 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 
[ 1381.167849][ C3] ? __pfx_br_ip4_multicast_port_query_expired (net/bridge/br_multicast.c:1920) bridge 
[ 1381.167884][ C3] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5816) 
[ 1381.167891][ C3] ? 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) 
[ 1381.167896][ C3] ? __pfx_do_raw_spin_lock (kernel/locking/spinlock_debug.c:114) 
[ 1381.167899][ C3] ? lock_acquire (kernel/locking/lockdep.c:5824) 
[ 1381.167902][ C3] ? 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 
[ 1381.167942][ C3] ? br_multicast_port_query_expired (net/bridge/br_multicast.c:1917) bridge 
[ 1381.167975][ C3] ? __pfx_br_ip4_multicast_port_query_expired (net/bridge/br_multicast.c:1920) bridge 
[ 1381.168009][ C3] br_multicast_port_query_expired (net/bridge/br_multicast.c:1917) bridge 
[ 1381.168046][ C3] ? __pfx_br_ip4_multicast_port_query_expired (net/bridge/br_multicast.c:1920) bridge 
[ 1381.168081][ C3] call_timer_fn (kernel/time/timer.c:1789) 
[ 1381.168085][ C3] ? call_timer_fn (./include/linux/lockdep.h:31 kernel/time/timer.c:1779) 
[ 1381.168088][ C3] ? call_timer_fn (./include/linux/lockdep.h:31 kernel/time/timer.c:1779) 
[ 1381.168092][ C3] ? __pfx_call_timer_fn (kernel/time/timer.c:1766) 
[ 1381.168096][ C3] ? 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) 
[ 1381.168105][ C3] ? mark_held_locks (kernel/locking/lockdep.c:4323) 
[ 1381.168117][ C3] __run_timers (kernel/time/timer.c:1841 kernel/time/timer.c:2414) 
[ 1381.168121][ C3] ? __pfx_br_ip4_multicast_port_query_expired (net/bridge/br_multicast.c:1920) bridge 
[ 1381.168163][ C3] ? __pfx___run_timers (kernel/time/timer.c:2385) 
[ 1381.168172][ C3] ? 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) 
[ 1381.168177][ C3] ? __pfx_do_raw_spin_lock (kernel/locking/spinlock_debug.c:114) 
[ 1381.168181][ C3] ? lock_acquire (kernel/locking/lockdep.c:5824) 
[ 1381.168183][ C3] ? run_timer_softirq (kernel/time/timer.c:2426 kernel/time/timer.c:2418 kernel/time/timer.c:2435 kernel/time/timer.c:2445) 
[ 1381.168194][ C3] run_timer_softirq (kernel/time/timer.c:2427 kernel/time/timer.c:2418 kernel/time/timer.c:2435 kernel/time/timer.c:2445) 
[ 1381.168199][ C3] handle_softirqs (kernel/softirq.c:561) 
[ 1381.168209][ C3] ? br_device_event (net/bridge/br.c:97) bridge 
[ 1381.168240][ C3] do_softirq (kernel/softirq.c:462 kernel/softirq.c:449) 
[ 1381.168243][    C3]  </IRQ>
[ 1381.168244][    C3]  <TASK>
[ 1381.168246][ C3] __local_bh_enable_ip (kernel/softirq.c:389) 
[ 1381.168251][ C3] br_device_event (net/bridge/br.c:97) bridge 
[ 1381.168281][ C3] ? __pfx_br_device_event (net/bridge/br.c:29) bridge 
[ 1381.168313][ C3] ? packet_notifier (net/packet/af_packet.c:4281) 
[ 1381.168324][ C3] notifier_call_chain (kernel/notifier.c:85 (discriminator 2)) 
[ 1381.168336][ C3] netdev_state_change (net/core/dev.c:1538 net/core/dev.c:1529) 
[ 1381.168340][ C3] ? __pfx_netdev_state_change (net/core/dev.c:1530) 
[ 1381.168355][ C3] linkwatch_do_dev (net/core/link_watch.c:186) 
[ 1381.168360][ C3] __linkwatch_run_queue (./include/linux/spinlock.h:376 net/core/link_watch.c:245) 
[ 1381.168367][ C3] ? __pfx___linkwatch_run_queue (net/core/link_watch.c:195) 
[ 1381.168374][ C3] ? lock_acquire (kernel/locking/lockdep.c:5824) 
[ 1381.168384][ C3] linkwatch_event (net/core/link_watch.c:287) 
[ 1381.168386][ C3] process_one_work (kernel/workqueue.c:3238) 
[ 1381.168400][ C3] ? __pfx___lock_release (kernel/locking/lockdep.c:5503) 
[ 1381.168405][ C3] ? __pfx_process_one_work (kernel/workqueue.c:3140) 
[ 1381.168419][ C3] ? assign_work (kernel/workqueue.c:1200) 
[ 1381.168429][ C3] worker_thread (kernel/workqueue.c:3313 kernel/workqueue.c:3400) 
[ 1381.168433][ C3] ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:4349 kernel/locking/lockdep.c:4408) 
[ 1381.168445][ C3] ? __pfx_worker_thread (kernel/workqueue.c:3346) 
[ 1381.168451][ C3] kthread (kernel/kthread.c:464) 
[ 1381.168455][ C3] ? __pfx_kthread (kernel/kthread.c:413) 
[ 1381.168464][ C3] ? __pfx_kthread (kernel/kthread.c:413) 
[ 1381.168470][ C3] ret_from_fork (arch/x86/kernel/process.c:148) 
[ 1381.168474][ C3] ? __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