======================================
| xx__-> echo $?
| 0
| xx__-> [   28.474229][   T50] BUG: spinlock bad magic on CPU#2, kworker/2:1/50
| [ 28.474471][ T50] lock: noop_qdisc+0x240/0x300, .magic: 00000000, .owner: kworker/2:1/50, .owner_cpu: 2 
[   28.474951][   T50] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[   28.475251][   T50] Workqueue: mld mld_ifc_work
[   28.475400][   T50] Call Trace:
[   28.475504][   T50]  <TASK>
[ 28.475570][ T50] dump_stack_lvl (lib/dump_stack.c:122) 
[ 28.475703][ T50] do_raw_spin_unlock (kernel/locking/spinlock_debug.c:100 kernel/locking/spinlock_debug.c:141) 
[ 28.475834][ T50] _raw_spin_unlock (./arch/x86/include/asm/preempt.h:94 ./include/linux/spinlock_api_smp.h:143 kernel/locking/spinlock.c:186) 
[ 28.475965][ T50] __dev_xmit_skb (./include/net/sch_generic.h:226 ./include/net/sch_generic.h:217 net/core/dev.c:3879) 
[ 28.476091][ T50] ? __pfx___dev_xmit_skb (net/core/dev.c:3784) 
[ 28.476218][ T50] ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:4291 kernel/locking/lockdep.c:4358) 
[ 28.476399][ T50] __dev_queue_xmit (net/core/dev.c:4389) 
[ 28.476528][ T50] ? __lock_release (kernel/locking/lockdep.c:5435) 
[ 28.476656][ T50] ? ip6_finish_output2 (./include/net/neighbour.h:542 net/ipv6/ip6_output.c:137) 
[ 28.476806][ T50] ? __pfx___lock_release (kernel/locking/lockdep.c:5411) 
[ 28.476943][ T50] ? __pfx___dev_queue_xmit (net/core/dev.c:4332) 
[ 28.477071][ T50] ? mark_held_locks (kernel/locking/lockdep.c:4273) 
[ 28.477212][ T50] ? eth_header (net/ethernet/eth.c:100) 
[ 28.477341][ T50] ? neigh_resolve_output (./include/linux/netdevice.h:3159 net/core/neighbour.c:1560 net/core/neighbour.c:1545) 
[ 28.477468][ T50] ip6_finish_output2 (./include/net/neighbour.h:542 net/ipv6/ip6_output.c:137) 
[ 28.477601][ T50] ip6_finish_output (net/ipv6/ip6_output.c:211 net/ipv6/ip6_output.c:222) 
[ 28.477728][ T50] ip6_output (./include/linux/netfilter.h:303 net/ipv6/ip6_output.c:243) 
[ 28.477862][ T50] ? __pfx_ip6_output (net/ipv6/ip6_output.c:230) 
[ 28.477989][ T50] ? lock_acquire.part.0 (kernel/locking/lockdep.c:466 kernel/locking/lockdep.c:5761) 
[ 28.478133][ T50] ? find_held_lock (kernel/locking/lockdep.c:5249) 
[ 28.478264][ T50] ? __lock_release (kernel/locking/lockdep.c:5435) 
[ 28.478411][ T50] ? icmp6_dst_alloc (net/ipv6/route.c:3295) 
[ 28.478556][ T50] NF_HOOK.constprop.0 (./include/linux/rcupdate.h:326 ./include/linux/rcupdate.h:838 ./include/linux/netfilter.h:238 ./include/linux/netfilter.h:312) 
[ 28.478686][ T50] ? __pfx_NF_HOOK.constprop.0 (./include/linux/netfilter.h:308) 
[ 28.478825][ T50] ? __pfx_xfrm_lookup_with_ifid (net/xfrm/xfrm_policy.c:3140) 
[ 28.479000][ T50] ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:4299 kernel/locking/lockdep.c:4358) 
[ 28.479191][ T50] ? icmp6_dst_alloc (net/ipv6/route.c:3295) 
[ 28.479315][ T50] ? __local_bh_enable_ip (./arch/x86/include/asm/irqflags.h:42 ./arch/x86/include/asm/irqflags.h:97 kernel/softirq.c:387) 
[ 28.479460][ T50] mld_sendpack (net/ipv6/mcast.c:1822) 
[ 28.479590][ T50] ? __pfx_mld_sendpack (net/ipv6/mcast.c:1779) 
[ 28.479734][ T50] ? mld_send_cr (net/ipv6/mcast.c:2096 (discriminator 11)) 
[ 28.479860][ T50] mld_ifc_work (net/ipv6/mcast.c:2652) 
[ 28.479986][ T50] process_one_work (kernel/workqueue.c:3231) 
[ 28.480146][ T50] ? __pfx___lock_release (kernel/locking/lockdep.c:5411) 
[ 28.480269][ T50] ? __pfx_process_one_work (kernel/workqueue.c:3133) 
[ 28.480409][ T50] ? assign_work (kernel/workqueue.c:1202) 
[ 28.480549][ T50] worker_thread (kernel/workqueue.c:3306 kernel/workqueue.c:3390) 
[ 28.480673][ T50] ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:4299 kernel/locking/lockdep.c:4358) 
[ 28.480843][ T50] ? __pfx_worker_thread (kernel/workqueue.c:3339) 
[ 28.480967][ T50] ? __pfx_worker_thread (kernel/workqueue.c:3339) 
[ 28.481106][ T50] kthread (kernel/kthread.c:389) 
[ 28.481202][ T50] ? __pfx_kthread (kernel/kthread.c:342) 
[ 28.481345][ T50] ret_from_fork (arch/x86/kernel/process.c:147) 
[ 28.481470][ T50] ? __pfx_kthread (kernel/kthread.c:342) 


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