======================================
| xx__-> echo $?
| 0
| xx__-> [   26.618686][    C2] BUG: spinlock bad magic on CPU#2, kworker/2:1/52
| [ 26.618987][ C2] lock: noop_qdisc+0x240/0x300, .magic: 00000000, .owner: kworker/2:1/52, .owner_cpu: 2 
[   26.619686][    C2] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[   26.620125][    C2] Workqueue: events linkwatch_event
[   26.620345][    C2] Call Trace:
[   26.620506][    C2]  <IRQ>
[ 26.620616][ C2] dump_stack_lvl (lib/dump_stack.c:122) 
[ 26.620830][ C2] do_raw_spin_unlock (kernel/locking/spinlock_debug.c:100 kernel/locking/spinlock_debug.c:141) 
[ 26.621028][ C2] _raw_spin_unlock (./arch/x86/include/asm/preempt.h:94 ./include/linux/spinlock_api_smp.h:143 kernel/locking/spinlock.c:186) 
[ 26.621230][ C2] net_tx_action (./include/net/sch_generic.h:226 ./include/net/sch_generic.h:217 ./include/net/pkt_sched.h:128 ./include/net/pkt_sched.h:124 net/core/dev.c:5323) 
[ 26.621413][ C2] handle_softirqs (kernel/softirq.c:554) 
[ 26.621581][ C2] ? dev_deactivate_many (./include/linux/bottom_half.h:33 ./include/linux/netdevice.h:4448 net/sched/sch_generic.c:571 net/sched/sch_generic.c:1363) 
[ 26.621748][ C2] do_softirq (kernel/softirq.c:455 kernel/softirq.c:442) 
[   26.621868][    C2]  </IRQ>
[   26.621950][    C2]  <TASK>
[ 26.622029][ C2] __local_bh_enable_ip (kernel/softirq.c:382) 
[ 26.622197][ C2] dev_deactivate_many (net/sched/sch_generic.c:1356) 
[ 26.622359][ C2] ? __lock_release (kernel/locking/lockdep.c:5435) 
[ 26.622515][ C2] ? __linkwatch_run_queue (net/core/link_watch.c:234) 
[ 26.622678][ C2] dev_deactivate (./include/linux/list.h:111 ./include/linux/list.h:215 ./include/linux/list.h:229 net/sched/sch_generic.c:1398) 
[ 26.622841][ C2] ? __pfx_dev_deactivate (net/sched/sch_generic.c:1393) 
[ 26.622997][ C2] ? mark_held_locks (kernel/locking/lockdep.c:4273) 
[ 26.623159][ C2] linkwatch_do_dev (net/core/link_watch.c:177) 
[ 26.623318][ C2] __linkwatch_run_queue (./include/linux/spinlock.h:376 net/core/link_watch.c:236) 
[ 26.623471][ C2] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 52)) 
[ 26.623630][ C2] ? __pfx___linkwatch_run_queue (net/core/link_watch.c:186) 
[ 26.623831][ C2] ? process_one_work (kernel/workqueue.c:3207) 
[ 26.623988][ C2] ? lock_acquire (kernel/locking/lockdep.c:5732) 
[ 26.624149][ C2] linkwatch_event (net/core/link_watch.c:278) 
[ 26.624306][ C2] process_one_work (kernel/workqueue.c:3231) 
[ 26.624465][ C2] ? __pfx___lock_release (kernel/locking/lockdep.c:5411) 
[ 26.624626][ C2] ? __pfx_process_one_work (kernel/workqueue.c:3133) 
[ 26.624819][ C2] ? assign_work (kernel/workqueue.c:1202) 
[ 26.624995][ C2] worker_thread (kernel/workqueue.c:3306 kernel/workqueue.c:3390) 
[ 26.625167][ C2] ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:4299 kernel/locking/lockdep.c:4358) 
[ 26.625379][ C2] ? __pfx_worker_thread (kernel/workqueue.c:3339) 
[ 26.625550][ C2] ? __pfx_worker_thread (kernel/workqueue.c:3339) 
[ 26.625720][ C2] kthread (kernel/kthread.c:389) 
[ 26.625854][ C2] ? __pfx_kthread (kernel/kthread.c:342) 
[ 26.626023][ C2] ret_from_fork (arch/x86/kernel/process.c:147) 
[ 26.626196][ C2] ? __pfx_kthread (kernel/kthread.c:342) 


Finger prints:
do_raw_spin_unlock:_raw_spin_unlock:net_tx_action:handle_softirqs:do_softirq