======================================
| [ 36.327108][ C2] ret_from_fork_asm (arch/x86/entry/entry_64.S:256) 
| [   36.327287][    C2]
| [   36.327377][    C2]
| [   36.327377][    C2] stack backtrace:
[   36.327871][    C2] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[   36.328281][    C2] Workqueue: ipv6_addrconf addrconf_dad_work
[   36.328515][    C2] Call Trace:
[   36.328652][    C2]  <IRQ>
[ 36.328746][ C2] dump_stack_lvl (lib/dump_stack.c:117) 
[ 36.328933][ C2] print_irq_inversion_bug.part.0 (kernel/locking/lockdep.c:4024) 
[ 36.329166][ C2] ? ret_from_fork_asm (arch/x86/entry/entry_64.S:256) 
[ 36.329347][ C2] ? __pfx_print_irq_inversion_bug.part.0 (kernel/locking/lockdep.c:4024) 
[ 36.329568][ C2] ? __pfx_usage_skip (kernel/locking/lockdep.c:2264) 
[ 36.329752][ C2] ? __pfx_usage_match (kernel/locking/lockdep.c:2256) 
[ 36.329931][ C2] ? arch_stack_walk (arch/x86/kernel/stacktrace.c:24) 
[ 36.330116][ C2] mark_lock_irq (kernel/locking/lockdep.c:4244) 
[ 36.330300][ C2] ? __pfx_mark_lock_irq (kernel/locking/lockdep.c:4207) 
[ 36.330481][ C2] ? stack_trace_save (kernel/stacktrace.c:123) 
[ 36.330666][ C2] ? save_trace (kernel/locking/lockdep.c:586) 
[ 36.330852][ C2] mark_lock (kernel/locking/lockdep.c:4678) 
[ 36.330988][ C2] mark_usage (kernel/locking/lockdep.c:4567) 
[ 36.331124][ C2] __lock_acquire (kernel/locking/lockdep.c:5091) 
[ 36.331311][ C2] lock_acquire.part.0 (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:5756) 
[ 36.331494][ C2] ? ipv6_get_lladdr (net/ipv6/addrconf.c:1911 net/ipv6/addrconf.c:1934) 
[ 36.331686][ C2] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5719) 
[ 36.331865][ C2] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 52)) 
[ 36.332045][ C2] ? ipv6_get_lladdr (net/ipv6/addrconf.c:1911 net/ipv6/addrconf.c:1934) 
[ 36.332222][ C2] ? lock_acquire (kernel/locking/lockdep.c:5727) 
[ 36.332402][ C2] ? ipv6_get_lladdr (net/ipv6/addrconf.c:1911 net/ipv6/addrconf.c:1934) 
[ 36.332582][ C2] _raw_read_lock_bh (./include/linux/rwlock_api_smp.h:177 kernel/locking/spinlock.c:252) 
[ 36.332766][ C2] ? ipv6_get_lladdr (net/ipv6/addrconf.c:1911 net/ipv6/addrconf.c:1934) 
[ 36.332946][ C2] ipv6_get_lladdr (net/ipv6/addrconf.c:1911 net/ipv6/addrconf.c:1934) 
[ 36.333125][ C2] ndisc_send_ns (net/ipv6/ndisc.c:658) 
[ 36.333303][ C2] ? __pfx_ndisc_send_ns (net/ipv6/ndisc.c:653) 
[ 36.333482][ C2] ? __ipv6_chk_addr_and_flags (net/ipv6/addrconf.c:2009) 
[ 36.333711][ C2] ndisc_solicit (net/ipv6/ndisc.c:736) 
[ 36.333891][ C2] ? __pfx_ndisc_solicit (net/ipv6/ndisc.c:736) 
[ 36.334070][ C2] ? neigh_probe (net/core/neighbour.c:1074) 
[ 36.334250][ C2] neigh_probe (net/core/neighbour.c:1075) 
[ 36.334390][ C2] __neigh_event_send (net/core/neighbour.c:1242) 
[ 36.334572][ C2] neigh_resolve_output (net/core/neighbour.c:1547) 
[ 36.334762][ C2] ? __local_bh_enable_ip (./arch/x86/include/asm/irqflags.h:42 ./arch/x86/include/asm/irqflags.h:77 kernel/softirq.c:387) 
[ 36.334943][ C2] ? ___neigh_create (net/core/neighbour.c:722 (discriminator 9)) 
[ 36.335127][ C2] ip6_finish_output2 (./include/net/neighbour.h:542 net/ipv6/ip6_output.c:137) 
[ 36.335309][ C2] ip6_finish_output (net/ipv6/ip6_output.c:211 net/ipv6/ip6_output.c:222) 
[ 36.335488][ C2] ip6_output (./include/linux/netfilter.h:303 net/ipv6/ip6_output.c:243) 
[ 36.335623][ C2] ? __pfx_ip6_output (net/ipv6/ip6_output.c:230) 
[ 36.335800][ C2] ? 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) 
[ 36.335986][ C2] ? ip6_mtu (./include/linux/rcupdate.h:339 ./include/linux/rcupdate.h:814 ./include/net/ip6_route.h:336 net/ipv6/route.c:3217) 
[ 36.336122][ C2] ? ip6_local_out (net/ipv6/output_core.c:154) 
[ 36.336305][ C2] udp_tunnel6_xmit_skb (./include/net/ip6_tunnel.h:163 net/ipv6/ip6_udp_tunnel.c:111) ip6_udp_tunnel
[ 36.336531][ C2] vxlan_xmit_one (drivers/net/vxlan/vxlan_core.c:2551) vxlan
[ 36.336726][ C2] ? find_held_lock (kernel/locking/lockdep.c:5244) 
[ 36.336904][ C2] ? migrate_device_coherent_page (./include/linux/pagemap.h:1069 mm/migrate_device.c:952) 
[ 36.337137][ C2] ? __pfx_vxlan_xmit_one (drivers/net/vxlan/vxlan_core.c:2313) vxlan
[ 36.337376][ C2] ? mark_held_locks (kernel/locking/lockdep.c:4274) 
[ 36.337556][ C2] ? lockdep_hardirqs_on_prepare.part.0 (kernel/locking/lockdep.c:4292 kernel/locking/lockdep.c:4359) 
[ 36.337782][ C2] ? kmem_cache_alloc (mm/slub.c:3858) 
[ 36.337962][ C2] ? __copy_skb_header (./include/net/dst.h:290 net/core/skbuff.c:1501) 
[ 36.338150][ C2] ? vxlan_xmit (drivers/net/vxlan/vxlan_core.c:2763) vxlan
[ 36.338345][ C2] vxlan_xmit (drivers/net/vxlan/vxlan_core.c:2763) vxlan
[ 36.338540][ C2] dev_hard_start_xmit (./include/linux/netdevice.h:4875 ./include/linux/netdevice.h:4889 net/core/dev.c:3563 net/core/dev.c:3579) 
[ 36.338721][ C2] ? validate_xmit_skb.constprop.0 (net/core/dev.c:3634) 
[ 36.338946][ C2] __dev_queue_xmit (net/core/dev.h:167 net/core/dev.c:4373) 
[ 36.339134][ C2] ? find_held_lock (kernel/locking/lockdep.c:5244) 
[ 36.339314][ C2] ? __pfx___dev_queue_xmit (net/core/dev.c:4281) 
[ 36.339495][ C2] ? __lock_release (kernel/locking/lockdep.c:5430) 
[ 36.339675][ C2] ? __pfx___lock_release (kernel/locking/lockdep.c:5406) 
[ 36.339854][ C2] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5719) 
[ 36.340038][ C2] br_dev_queue_push_xmit (net/bridge/br_forward.c:34) bridge
[ 36.340297][ C2] ? __pfx_br_dev_queue_push_xmit (net/bridge/br_forward.c:34) bridge
[ 36.340557][ C2] ? __br_forward (./include/linux/netfilter.h:314 ./include/linux/netfilter.h:308 net/bridge/br_forward.c:115) bridge
[ 36.340771][ C2] deliver_clone (net/bridge/br_forward.c:132) bridge
[ 36.340985][ C2] br_handle_frame_finish (net/bridge/br_input.c:215) bridge
[ 36.341243][ C2] ? __pfx_br_handle_frame_finish (net/bridge/br_input.c:75) bridge
[ 36.341497][ C2] ? usage_skip (kernel/locking/lockdep.c:2295 kernel/locking/lockdep.c:2263) 
[ 36.341684][ C2] ? validate_chain (./include/linux/hash.h:78 kernel/locking/lockdep.c:3759 kernel/locking/lockdep.c:3782 kernel/locking/lockdep.c:3837) 
[ 36.341871][ C2] br_handle_frame (net/bridge/br_input.c:417) bridge
[ 36.342089][ C2] ? __pfx_br_handle_frame (net/bridge/br_input.c:321) bridge
[ 36.342346][ C2] __netif_receive_skb_core.constprop.0 (net/core/dev.c:5498) 
[ 36.342574][ C2] ? mark_lock (kernel/locking/lockdep.c:4656 (discriminator 3)) 
[ 36.342839][ C2] ? __lock_acquire (kernel/locking/lockdep.c:5137) 
[ 36.343023][ C2] ? __pfx___netif_receive_skb_core.constprop.0 (net/core/dev.c:5391) 
[ 36.343249][ C2] ? lock_acquire.part.0 (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:5756) 
[ 36.343428][ C2] ? process_backlog (./include/linux/rcupdate.h:329 ./include/linux/rcupdate.h:781 net/core/dev.c:6046) 
[ 36.343744][ C2] __netif_receive_skb_one_core (net/core/dev.c:5603) 
[ 36.343968][ C2] ? __pfx___netif_receive_skb_one_core (net/core/dev.c:5597) 
[ 36.344190][ C2] ? process_backlog (./include/linux/rcupdate.h:329 ./include/linux/rcupdate.h:781 net/core/dev.c:6046) 
[ 36.344372][ C2] ? lock_acquire (kernel/locking/lockdep.c:5727) 
[ 36.344686][ C2] ? process_backlog (./include/linux/rcupdate.h:329 ./include/linux/rcupdate.h:781 net/core/dev.c:6046) 
[ 36.344868][ C2] process_backlog (./include/linux/rcupdate.h:810 net/core/dev.c:6048) 
[ 36.345047][ C2] ? find_held_lock (kernel/locking/lockdep.c:5244) 
[ 36.345225][ C2] __napi_poll.constprop.0 (net/core/dev.c:6701) 
[ 36.345538][ C2] net_rx_action (net/core/dev.c:6770 net/core/dev.c:6886) 
[ 36.345722][ C2] ? __pfx_net_rx_action (net/core/dev.c:6850) 
[ 36.345908][ C2] ? usage_skip (kernel/locking/lockdep.c:2295 kernel/locking/lockdep.c:2263) 
[ 36.346088][ C2] ? mark_held_locks (kernel/locking/lockdep.c:4274) 
[ 36.346269][ C2] __do_softirq (kernel/softirq.c:554) 
[ 36.346452][ C2] ? __dev_queue_xmit (./include/linux/rcupdate.h:339 ./include/linux/rcupdate.h:849 net/core/dev.c:4399) 
[ 36.346643][ C2] do_softirq (kernel/softirq.c:455 kernel/softirq.c:442) 
[   36.346780][    C2]  </IRQ>
[   36.346872][    C2]  <TASK>
[ 36.346963][ C2] __local_bh_enable_ip (kernel/softirq.c:382) 
[ 36.347276][ C2] ? __dev_queue_xmit (./include/linux/rcupdate.h:339 ./include/linux/rcupdate.h:849 net/core/dev.c:4399) 
[ 36.347468][ C2] __dev_queue_xmit (net/core/dev.c:4400) 
[ 36.347648][ C2] ? mark_lock (kernel/locking/lockdep.c:4656 (discriminator 3)) 
[ 36.347783][ C2] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 52)) 
[ 36.347964][ C2] ? mark_held_locks (kernel/locking/lockdep.c:4274) 
[ 36.348272][ C2] ? eth_header (net/ethernet/eth.c:100) 
[ 36.348454][ C2] ? __pfx___dev_queue_xmit (net/core/dev.c:4281) 
[ 36.348637][ C2] ip6_finish_output2 (./include/net/neighbour.h:542 net/ipv6/ip6_output.c:137) 
[ 36.348824][ C2] ip6_finish_output (net/ipv6/ip6_output.c:211 net/ipv6/ip6_output.c:222) 
[ 36.349127][ 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:228) 
[ 36.349307][ C2] ip6_output (./include/linux/netfilter.h:303 net/ipv6/ip6_output.c:243) 
[ 36.349442][ C2] ? __pfx_ip6_output (net/ipv6/ip6_output.c:230) 
[ 36.349622][ C2] ? lock_acquire.part.0 (kernel/locking/lockdep.c:5719) 
[ 36.349945][ C2] NF_HOOK.constprop.0 (./include/linux/rcupdate.h:329 ./include/linux/rcupdate.h:781 ./include/linux/netfilter.h:238 ./include/linux/netfilter.h:312) 
[ 36.350128][ C2] ? ndisc_send_skb (./include/linux/rcupdate.h:339 ./include/linux/rcupdate.h:814 net/ipv6/ndisc.c:455 net/ipv6/ndisc.c:503) 
[ 36.350306][ C2] ? __pfx_NF_HOOK.constprop.0 (./include/linux/netfilter.h:308) 
[ 36.350493][ C2] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5719) 
[ 36.350676][ C2] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 52)) 
[ 36.350984][ C2] ndisc_send_skb (net/ipv6/ndisc.c:512 (discriminator 60)) 
[ 36.351166][ C2] ? __pfx_ndisc_send_skb (net/ipv6/ndisc.c:473) 
[ 36.351349][ C2] ndisc_send_ns (net/ipv6/ndisc.c:653) 
[ 36.351539][ C2] ? mark_lock (kernel/locking/lockdep.c:4656 (discriminator 3)) 
[ 36.351814][ C2] ? __pfx_ndisc_send_ns (net/ipv6/ndisc.c:653) 
[ 36.351996][ C2] ? mark_held_locks (kernel/locking/lockdep.c:4274) 
[ 36.352177][ C2] ? lockdep_hardirqs_on_prepare.part.0 (kernel/locking/lockdep.c:4300 kernel/locking/lockdep.c:4359) 
[ 36.352401][ C2] addrconf_dad_work (net/ipv6/addrconf.c:4280) 
[ 36.352707][ C2] ? __pfx_addrconf_dad_work (net/ipv6/addrconf.c:4178) 
[ 36.352884][ C2] ? process_one_work (kernel/workqueue.c:3230) 
[ 36.353061][ C2] ? lock_acquire (kernel/locking/lockdep.c:5727) 
[ 36.353237][ C2] ? process_one_work (kernel/workqueue.c:3230) 
[ 36.353415][ C2] process_one_work (kernel/workqueue.c:3254) 
[ 36.353596][ C2] ? __pfx___lock_release (kernel/locking/lockdep.c:5406) 
[ 36.353779][ C2] ? __pfx_process_one_work (kernel/workqueue.c:3156) 
[ 36.353960][ C2] ? assign_work (kernel/workqueue.c:1209) 
[ 36.354140][ C2] worker_thread (kernel/workqueue.c:3329 kernel/workqueue.c:3416) 
[ 36.354443][ C2] ? __pfx_worker_thread (kernel/workqueue.c:3362) 
[ 36.354620][ C2] kthread (kernel/kthread.c:388) 
[ 36.354756][ C2] ? __pfx_kthread (kernel/kthread.c:341) 
[ 36.354937][ C2] ret_from_fork (arch/x86/kernel/process.c:147) 
[ 36.355239][ C2] ? __pfx_kthread (kernel/kthread.c:341) 


Finger prints:
ret_from_fork_asm:dump_stack_lvl:mark_lock_irq:mark_lock