======================================
| xx__-> echo $?
| 0
| xx__-> [   31.397113][   T51] BUG: spinlock bad magic on CPU#2, kworker/2:1/51
| [ 31.397322][ T51] lock: noop_qdisc+0x240/0x300, .magic: 00000000, .owner: kworker/2:1/51, .owner_cpu: 2 
[   31.397789][   T51] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[   31.398091][   T51] Workqueue: mld mld_ifc_work
[   31.398235][   T51] Call Trace:
[   31.398340][   T51]  <TASK>
[ 31.398410][ T51] dump_stack_lvl (lib/dump_stack.c:122) 
[ 31.398553][ T51] do_raw_spin_unlock (kernel/locking/spinlock_debug.c:100 kernel/locking/spinlock_debug.c:141) 
[ 31.398692][ T51] _raw_spin_unlock (./arch/x86/include/asm/preempt.h:94 ./include/linux/spinlock_api_smp.h:143 kernel/locking/spinlock.c:186) 
[ 31.398829][ T51] __dev_xmit_skb (./include/net/sch_generic.h:226 ./include/net/sch_generic.h:217 net/core/dev.c:3879) 
[ 31.399000][ T51] ? __pfx___dev_xmit_skb (net/core/dev.c:3784) 
[ 31.399139][ T51] ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:4291 kernel/locking/lockdep.c:4358) 
[ 31.399311][ T51] __dev_queue_xmit (net/core/dev.c:4389) 
[ 31.399447][ T51] ? __lock_release (kernel/locking/lockdep.c:5435) 
[ 31.399580][ T51] ? ip6_finish_output2 (./include/net/neighbour.h:542 net/ipv6/ip6_output.c:137) 
[ 31.399717][ T51] ? __pfx___lock_release (kernel/locking/lockdep.c:5411) 
[ 31.399853][ T51] ? __pfx___dev_queue_xmit (net/core/dev.c:4332) 
[ 31.399992][ T51] ? mark_held_locks (kernel/locking/lockdep.c:4273) 
[ 31.400127][ T51] ? eth_header (net/ethernet/eth.c:100) 
[ 31.400266][ T51] ? neigh_resolve_output (./include/linux/netdevice.h:3159 net/core/neighbour.c:1560 net/core/neighbour.c:1545) 
[ 31.400406][ T51] ip6_finish_output2 (./include/net/neighbour.h:542 net/ipv6/ip6_output.c:137) 
[ 31.400541][ T51] ip6_finish_output (net/ipv6/ip6_output.c:211 net/ipv6/ip6_output.c:222) 
[ 31.400677][ T51] ip6_output (./include/linux/netfilter.h:303 net/ipv6/ip6_output.c:243) 
[ 31.400780][ T51] ? __pfx_ip6_output (net/ipv6/ip6_output.c:230) 
[ 31.400915][ T51] ? lock_acquire.part.0 (kernel/locking/lockdep.c:466 kernel/locking/lockdep.c:5761) 
[ 31.401047][ T51] ? find_held_lock (kernel/locking/lockdep.c:5249) 
[ 31.401186][ T51] ? __lock_release (kernel/locking/lockdep.c:5435) 
[ 31.401324][ T51] ? icmp6_dst_alloc (net/ipv6/route.c:3295) 
[ 31.401535][ T51] NF_HOOK.constprop.0 (./include/linux/rcupdate.h:326 ./include/linux/rcupdate.h:838 ./include/linux/netfilter.h:238 ./include/linux/netfilter.h:312) 
[ 31.401659][ T51] ? __pfx_NF_HOOK.constprop.0 (./include/linux/netfilter.h:308) 
[ 31.401840][ T51] ? __pfx_xfrm_lookup_with_ifid (net/xfrm/xfrm_policy.c:3140) 
[ 31.402020][ T51] ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:4299 kernel/locking/lockdep.c:4358) 
[ 31.402173][ T51] ? icmp6_dst_alloc (net/ipv6/route.c:3295) 
[ 31.402310][ T51] ? __local_bh_enable_ip (./arch/x86/include/asm/irqflags.h:42 ./arch/x86/include/asm/irqflags.h:97 kernel/softirq.c:387) 
[ 31.402437][ T51] mld_sendpack (net/ipv6/mcast.c:1822) 
[ 31.402561][ T51] ? __pfx_mld_sendpack (net/ipv6/mcast.c:1779) 
[ 31.402689][ T51] ? mld_send_cr (net/ipv6/mcast.c:2096 (discriminator 11)) 
[ 31.402822][ T51] mld_ifc_work (net/ipv6/mcast.c:2652) 
[ 31.402943][ T51] process_one_work (kernel/workqueue.c:3231) 
[ 31.403069][ T51] ? __pfx___lock_release (kernel/locking/lockdep.c:5411) 
[ 31.403196][ T51] ? __pfx_process_one_work (kernel/workqueue.c:3133) 
[ 31.403320][ T51] ? assign_work (kernel/workqueue.c:1202) 
[ 31.403441][ T51] worker_thread (kernel/workqueue.c:3306 kernel/workqueue.c:3390) 
[ 31.403567][ T51] ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:4299 kernel/locking/lockdep.c:4358) 
[ 31.403719][ T51] ? __pfx_worker_thread (kernel/workqueue.c:3339) 
[ 31.403840][ T51] ? __pfx_worker_thread (kernel/workqueue.c:3339) 
[ 31.403963][ T51] kthread (kernel/kthread.c:389) 
[ 31.404074][ T51] ? __pfx_kthread (kernel/kthread.c:342) 
[ 31.404203][ T51] ret_from_fork (arch/x86/kernel/process.c:147) 
[ 31.404331][ T51] ? __pfx_kthread (kernel/kthread.c:342) 


Finger prints:
do_raw_spin_unlock:_raw_spin_unlock:__dev_xmit_skb:__dev_queue_xmit:ip6_finish_output2