======================================
| [ 38.906762][ C3] ret_from_fork_asm (arch/x86/entry/entry_64.S:256) 
| [   38.906997][    C3]
| [   38.907105][    C3]
| [   38.907105][    C3] stack backtrace:
[   38.907714][    C3] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[   38.908238][    C3] Workqueue: mld mld_ifc_work
[   38.908518][    C3] Call Trace:
[   38.908695][    C3]  <IRQ>
[ 38.908843][ C3] dump_stack_lvl (lib/dump_stack.c:117) 
[ 38.909136][ C3] print_irq_inversion_bug.part.0 (kernel/locking/lockdep.c:4024) 
[ 38.909447][ C3] ? ret_from_fork_asm (arch/x86/entry/entry_64.S:256) 
[ 38.909715][ C3] ? __pfx_print_irq_inversion_bug.part.0 (kernel/locking/lockdep.c:4024) 
[ 38.910041][ C3] ? __pfx_usage_skip (kernel/locking/lockdep.c:2264) 
[ 38.910329][ C3] ? __pfx_usage_match (kernel/locking/lockdep.c:2256) 
[ 38.910611][ C3] ? arch_stack_walk (arch/x86/kernel/stacktrace.c:24) 
[ 38.910899][ C3] mark_lock_irq (kernel/locking/lockdep.c:4244) 
[ 38.911206][ C3] ? __pfx_mark_lock_irq (kernel/locking/lockdep.c:4207) 
[ 38.911502][ C3] ? stack_trace_save (kernel/stacktrace.c:123) 
[ 38.911792][ C3] ? save_trace (kernel/locking/lockdep.c:586) 
[ 38.912075][ C3] mark_lock (kernel/locking/lockdep.c:4678) 
[ 38.912283][ C3] mark_usage (kernel/locking/lockdep.c:4567) 
[ 38.912492][ C3] __lock_acquire (kernel/locking/lockdep.c:5091) 
[ 38.912777][ C3] lock_acquire.part.0 (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:5756) 
[ 38.913063][ C3] ? ipv6_get_lladdr (net/ipv6/addrconf.c:1911 net/ipv6/addrconf.c:1934) 
[ 38.913344][ C3] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5719) 
[ 38.913625][ C3] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 52)) 
[ 38.913949][ C3] ? ipv6_get_lladdr (net/ipv6/addrconf.c:1911 net/ipv6/addrconf.c:1934) 
[ 38.914222][ C3] ? lock_acquire (kernel/locking/lockdep.c:5727) 
[ 38.914496][ C3] ? ipv6_get_lladdr (net/ipv6/addrconf.c:1911 net/ipv6/addrconf.c:1934) 
[ 38.914775][ C3] _raw_read_lock_bh (./include/linux/rwlock_api_smp.h:177 kernel/locking/spinlock.c:252) 
[ 38.915047][ C3] ? ipv6_get_lladdr (net/ipv6/addrconf.c:1911 net/ipv6/addrconf.c:1934) 
[ 38.915323][ C3] ipv6_get_lladdr (net/ipv6/addrconf.c:1911 net/ipv6/addrconf.c:1934) 
[ 38.915598][ C3] ndisc_send_ns (net/ipv6/ndisc.c:658) 
[ 38.915852][ C3] ? __pfx_ndisc_send_ns (net/ipv6/ndisc.c:653) 
[ 38.916157][ C3] ? __ipv6_chk_addr_and_flags (net/ipv6/addrconf.c:2009) 
[ 38.916459][ C3] ndisc_solicit (net/ipv6/ndisc.c:736) 
[ 38.916647][ C3] ? __pfx_ndisc_solicit (net/ipv6/ndisc.c:736) 
[ 38.916885][ C3] ? neigh_probe (net/core/neighbour.c:1074) 
[ 38.917072][ C3] neigh_probe (net/core/neighbour.c:1075) 
[ 38.917526][ C3] __neigh_event_send (net/core/neighbour.c:1242) 
[ 38.917732][ C3] neigh_resolve_output (net/core/neighbour.c:1547) 
[ 38.917962][ C3] ? __local_bh_enable_ip (./arch/x86/include/asm/irqflags.h:42 ./arch/x86/include/asm/irqflags.h:77 kernel/softirq.c:387) 
[ 38.918256][ C3] ? ___neigh_create (net/core/neighbour.c:722 (discriminator 9)) 
[ 38.918485][ C3] ip6_finish_output2 (./include/net/neighbour.h:542 net/ipv6/ip6_output.c:137) 
[ 38.918701][ C3] ip6_finish_output (net/ipv6/ip6_output.c:211 net/ipv6/ip6_output.c:222) 
[ 38.918983][ C3] ip6_output (./include/linux/netfilter.h:303 net/ipv6/ip6_output.c:243) 
[ 38.919132][ C3] ? __pfx_ip6_output (net/ipv6/ip6_output.c:230) 
[ 38.919429][ C3] ? pskb_expand_head (./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:2267) 
[ 38.919742][ C3] ? ip6_mtu (./include/linux/rcupdate.h:339 ./include/linux/rcupdate.h:814 ./include/net/ip6_route.h:336 net/ipv6/route.c:3217) 
[ 38.919948][ C3] ? ip6_local_out (net/ipv6/output_core.c:154) 
[ 38.920201][ C3] udp_tunnel6_xmit_skb (./include/net/ip6_tunnel.h:163 net/ipv6/ip6_udp_tunnel.c:111) ip6_udp_tunnel
[ 38.920564][ C3] vxlan_xmit_one (drivers/net/vxlan/vxlan_core.c:2551) vxlan
[ 38.921080][ C3] ? stack_access_ok (arch/x86/kernel/unwind_orc.c:396) 
[ 38.921363][ C3] ? ip6_fraglist_init (./include/linux/skbuff.h:2711 net/ipv6/ip6_output.c:715) 
[ 38.921666][ C3] ? __pfx_vxlan_xmit_one (drivers/net/vxlan/vxlan_core.c:2313) vxlan
[ 38.922112][ C3] ? __lock_acquire (kernel/locking/lockdep.c:5137) 
[ 38.922633][ C3] ? orc_sort_cmp (arch/x86/kernel/unwind_orc.c:80 arch/x86/kernel/unwind_orc.c:271) 
[ 38.922912][ C3] ? __dev_queue_xmit (./include/linux/bottom_half.h:20 ./include/linux/rcupdate.h:833 net/core/dev.c:4297) 
[ 38.923374][ C3] ? lock_acquire.part.0 (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:5756) 
[ 38.923579][ C3] ? vxlan_xmit (drivers/net/vxlan/vxlan_core.c:2766) vxlan
[ 38.923776][ C3] vxlan_xmit (drivers/net/vxlan/vxlan_core.c:2766) vxlan
[ 38.924000][ C3] dev_hard_start_xmit (./include/linux/netdevice.h:4875 ./include/linux/netdevice.h:4889 net/core/dev.c:3563 net/core/dev.c:3579) 
[ 38.924479][ C3] ? validate_xmit_skb.constprop.0 (net/core/dev.c:3634) 
[ 38.924718][ C3] __dev_queue_xmit (net/core/dev.h:167 net/core/dev.c:4373) 
[ 38.924916][ C3] ? find_held_lock (kernel/locking/lockdep.c:5244) 
[ 38.925107][ C3] ? __pfx___dev_queue_xmit (net/core/dev.c:4281) 
[ 38.925298][ C3] ? __lock_release (kernel/locking/lockdep.c:5430) 
[ 38.925518][ C3] ? __pfx___lock_release (kernel/locking/lockdep.c:5406) 
[ 38.925833][ C3] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5719) 
[ 38.926030][ C3] br_dev_queue_push_xmit (net/bridge/br_forward.c:34) bridge
[ 38.926334][ C3] ? __pfx_br_dev_queue_push_xmit (net/bridge/br_forward.c:34) bridge
[ 38.926635][ C3] ? __br_forward (./include/linux/netfilter.h:314 ./include/linux/netfilter.h:308 net/bridge/br_forward.c:115) bridge
[ 38.927007][ C3] deliver_clone (net/bridge/br_forward.c:132) bridge
[ 38.927239][ C3] br_handle_frame_finish (net/bridge/br_input.c:215) bridge
[ 38.927532][ C3] ? __pfx_br_handle_frame_finish (net/bridge/br_input.c:75) bridge
[ 38.927836][ C3] ? find_held_lock (kernel/locking/lockdep.c:5244) 
[ 38.928180][ C3] br_handle_frame (net/bridge/br_input.c:417) bridge
[ 38.928461][ C3] ? __pfx_br_handle_frame (net/bridge/br_input.c:321) bridge
[ 38.928756][ C3] __netif_receive_skb_core.constprop.0 (net/core/dev.c:5498) 
[ 38.929059][ C3] ? mark_lock (kernel/locking/lockdep.c:4656 (discriminator 3)) 
[ 38.929355][ C3] ? __lock_acquire (kernel/locking/lockdep.c:5137) 
[ 38.929564][ C3] ? __pfx___netif_receive_skb_core.constprop.0 (net/core/dev.c:5391) 
[ 38.929848][ C3] ? lock_acquire.part.0 (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:5756) 
[ 38.930056][ C3] ? process_backlog (./include/linux/rcupdate.h:329 ./include/linux/rcupdate.h:781 net/core/dev.c:6046) 
[ 38.930410][ C3] __netif_receive_skb_one_core (net/core/dev.c:5603) 
[ 38.930736][ C3] ? __pfx___netif_receive_skb_one_core (net/core/dev.c:5597) 
[ 38.931027][ C3] ? process_backlog (./include/linux/rcupdate.h:329 ./include/linux/rcupdate.h:781 net/core/dev.c:6046) 
[ 38.931223][ C3] ? lock_acquire (kernel/locking/lockdep.c:5727) 
[ 38.931416][ C3] ? process_backlog (./include/linux/rcupdate.h:329 ./include/linux/rcupdate.h:781 net/core/dev.c:6046) 
[ 38.931608][ C3] process_backlog (./include/linux/rcupdate.h:810 net/core/dev.c:6048) 
[ 38.931816][ C3] ? find_held_lock (kernel/locking/lockdep.c:5244) 
[ 38.932011][ C3] __napi_poll.constprop.0 (net/core/dev.c:6701) 
[ 38.932221][ C3] net_rx_action (net/core/dev.c:6770 net/core/dev.c:6886) 
[ 38.932416][ C3] ? __pfx_net_rx_action (net/core/dev.c:6850) 
[ 38.932616][ C3] ? usage_skip (kernel/locking/lockdep.c:2295 kernel/locking/lockdep.c:2263) 
[ 38.932806][ C3] ? mark_held_locks (kernel/locking/lockdep.c:4274) 
[ 38.933154][ C3] __do_softirq (kernel/softirq.c:554) 
[ 38.933353][ C3] ? __dev_queue_xmit (./include/linux/rcupdate.h:339 ./include/linux/rcupdate.h:849 net/core/dev.c:4399) 
[ 38.933545][ C3] do_softirq (kernel/softirq.c:455 kernel/softirq.c:442) 
[   38.933693][    C3]  </IRQ>
[   38.933791][    C3]  <TASK>
[ 38.933888][ C3] __local_bh_enable_ip (kernel/softirq.c:382) 
[ 38.934198][ C3] ? __dev_queue_xmit (./include/linux/rcupdate.h:339 ./include/linux/rcupdate.h:849 net/core/dev.c:4399) 
[ 38.934386][ C3] __dev_queue_xmit (net/core/dev.c:4400) 
[ 38.934579][ C3] ? mark_lock (kernel/locking/lockdep.c:4656 (discriminator 3)) 
[ 38.934724][ C3] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 52)) 
[ 38.935160][ C3] ? mark_held_locks (kernel/locking/lockdep.c:4274) 
[ 38.935349][ C3] ? eth_header (net/ethernet/eth.c:100) 
[ 38.935565][ C3] ? __pfx___dev_queue_xmit (net/core/dev.c:4281) 
[ 38.935764][ C3] ip6_finish_output2 (./include/net/neighbour.h:542 net/ipv6/ip6_output.c:137) 
[ 38.936080][ C3] ip6_finish_output (net/ipv6/ip6_output.c:211 net/ipv6/ip6_output.c:222) 
[ 38.936309][ C3] ip6_output (./include/linux/netfilter.h:303 net/ipv6/ip6_output.c:243) 
[ 38.936467][ C3] ? __pfx_ip6_output (net/ipv6/ip6_output.c:230) 
[ 38.936658][ C3] ? lock_acquire.part.0 (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:5756) 
[ 38.936868][ C3] ? find_held_lock (kernel/locking/lockdep.c:5244) 
[ 38.937202][ C3] ? __lock_release (kernel/locking/lockdep.c:5430) 
[ 38.937396][ C3] ? icmp6_dst_alloc (net/ipv6/route.c:3293) 
[ 38.937594][ C3] NF_HOOK.constprop.0 (./include/linux/rcupdate.h:329 ./include/linux/rcupdate.h:781 ./include/linux/netfilter.h:238 ./include/linux/netfilter.h:312) 
[ 38.937802][ C3] ? __pfx_NF_HOOK.constprop.0 (./include/linux/netfilter.h:308) 
[ 38.938113][ C3] ? __pfx_xfrm_lookup_with_ifid (net/xfrm/xfrm_policy.c:3136) 
[ 38.938351][ C3] ? lockdep_hardirqs_on_prepare.part.0 (kernel/locking/lockdep.c:4300 kernel/locking/lockdep.c:4359) 
[ 38.938617][ C3] ? icmp6_dst_alloc (net/ipv6/route.c:3293) 
[ 38.938809][ C3] ? __local_bh_enable_ip (./arch/x86/include/asm/irqflags.h:42 ./arch/x86/include/asm/irqflags.h:77 kernel/softirq.c:387) 
[ 38.939130][ C3] mld_sendpack (net/ipv6/mcast.c:1822) 
[ 38.939326][ C3] ? __pfx_mld_sendpack (net/ipv6/mcast.c:1779) 
[ 38.939538][ C3] ? __pfx___mutex_lock (kernel/locking/mutex.c:751) 
[ 38.939748][ C3] ? mld_send_cr (net/ipv6/mcast.c:2096 (discriminator 11)) 
[ 38.940070][ C3] mld_ifc_work (net/ipv6/mcast.c:2652) 
[ 38.940250][ C3] process_one_work (kernel/workqueue.c:3254) 
[ 38.940437][ C3] ? __pfx___lock_release (kernel/locking/lockdep.c:5406) 
[ 38.940651][ C3] ? __pfx_process_one_work (kernel/workqueue.c:3156) 
[ 38.940979][ C3] ? assign_work (kernel/workqueue.c:1209) 
[ 38.941160][ C3] worker_thread (kernel/workqueue.c:3329 kernel/workqueue.c:3416) 
[ 38.941341][ C3] ? lockdep_hardirqs_on_prepare.part.0 (kernel/locking/lockdep.c:4300 kernel/locking/lockdep.c:4359) 
[ 38.941604][ C3] ? __pfx_worker_thread (kernel/workqueue.c:3362) 
[ 38.941928][ C3] ? __pfx_worker_thread (kernel/workqueue.c:3362) 
[ 38.942119][ C3] kthread (kernel/kthread.c:388) 
[ 38.942323][ C3] ? __pfx_kthread (kernel/kthread.c:341) 
[ 38.942516][ C3] ret_from_fork (arch/x86/kernel/process.c:147) 
[ 38.942718][ C3] ? __pfx_kthread (kernel/kthread.c:341) 


Finger prints:
ret_from_fork_asm:dump_stack_lvl:mark_lock_irq:mark_lock