======================================
| xx__-> echo $?
| 0
| xx__-> [   31.050665][    T9] BUG: spinlock bad magic on CPU#0, kworker/0:1/9
| [ 31.050966][ T9] lock: noop_qdisc+0x240/0x300, .magic: 00000000, .owner: kworker/0:1/9, .owner_cpu: 0 
[   31.051636][    T9] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[   31.052135][    T9] Workqueue: mld mld_ifc_work
[   31.052364][    T9] Call Trace:
[   31.052523][    T9]  <TASK>
[ 31.052651][ T9] dump_stack_lvl (lib/dump_stack.c:122) 
[ 31.052866][ T9] do_raw_spin_unlock (kernel/locking/spinlock_debug.c:100 kernel/locking/spinlock_debug.c:141) 
[ 31.053090][ T9] _raw_spin_unlock (./arch/x86/include/asm/preempt.h:94 ./include/linux/spinlock_api_smp.h:143 kernel/locking/spinlock.c:186) 
[ 31.053305][ T9] __dev_xmit_skb (./include/net/sch_generic.h:226 ./include/net/sch_generic.h:217 net/core/dev.c:3879) 
[ 31.053528][ T9] ? __pfx___dev_xmit_skb (net/core/dev.c:3784) 
[ 31.053711][ T9] ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:4291 kernel/locking/lockdep.c:4358) 
[ 31.053936][ T9] ? __dev_queue_xmit (./include/linux/bottom_half.h:20 ./include/linux/rcupdate.h:890 net/core/dev.c:4348) 
[ 31.054117][ T9] __dev_queue_xmit (net/core/dev.c:4389) 
[ 31.054301][ T9] ? __lock_release (kernel/locking/lockdep.c:5435) 
[ 31.054489][ T9] ? ip6_finish_output2 (./include/net/neighbour.h:542 net/ipv6/ip6_output.c:137) 
[ 31.054676][ T9] ? __pfx___lock_release (kernel/locking/lockdep.c:5411) 
[ 31.054888][ T9] ? __pfx___dev_queue_xmit (net/core/dev.c:4332) 
[ 31.055099][ T9] ? mark_held_locks (kernel/locking/lockdep.c:4273) 
[ 31.055316][ T9] ? eth_header (net/ethernet/eth.c:100) 
[ 31.055514][ T9] ? neigh_resolve_output (./include/linux/netdevice.h:3159 net/core/neighbour.c:1560 net/core/neighbour.c:1545) 
[ 31.055705][ T9] ip6_finish_output2 (./include/net/neighbour.h:542 net/ipv6/ip6_output.c:137) 
[ 31.055887][ T9] ip6_finish_output.constprop.0 (net/ipv6/ip6_output.c:211 net/ipv6/ip6_output.c:222) 
[ 31.056113][ T9] mld_sendpack (net/ipv6/mcast.c:1822) 
[ 31.056311][ T9] ? __pfx_mld_sendpack (net/ipv6/mcast.c:1779) 
[ 31.056504][ T9] ? mld_send_cr (net/ipv6/mcast.c:2096 (discriminator 11)) 
[ 31.056702][ T9] mld_ifc_work (net/ipv6/mcast.c:2652) 
[ 31.056898][ T9] process_one_work (kernel/workqueue.c:3231) 
[ 31.057098][ T9] ? __pfx___lock_release (kernel/locking/lockdep.c:5411) 
[ 31.057282][ T9] ? __pfx_process_one_work (kernel/workqueue.c:3133) 
[ 31.057475][ T9] ? assign_work (kernel/workqueue.c:1202) 
[ 31.057659][ T9] worker_thread (kernel/workqueue.c:3306 kernel/workqueue.c:3390) 
[ 31.057844][ T9] ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:4299 kernel/locking/lockdep.c:4358) 
[ 31.058089][ T9] ? __pfx_worker_thread (kernel/workqueue.c:3339) 
[ 31.058277][ T9] ? __pfx_worker_thread (kernel/workqueue.c:3339) 
[ 31.058473][ T9] kthread (kernel/kthread.c:389) 
[ 31.058610][ T9] ? __pfx_kthread (kernel/kthread.c:342) 
[ 31.058799][ T9] ret_from_fork (arch/x86/kernel/process.c:147) 
[ 31.058974][ T9] ? __pfx_kthread (kernel/kthread.c:342) 


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