======================================
| xx__-> [   24.928106][  T244] gre: GRE over IPv4 demultiplexor driver
| [   27.011800][  T268] ip_gre: GRE over IPv4 tunneling driver
| [   29.440607][    C0] BUG: spinlock bad magic on CPU#0, kworker/u16:0/11
| [ 29.440804][ C0] lock: noop_qdisc+0x240/0x300, .magic: 00000000, .owner: kworker/u16:0/11, .owner_cpu: 0 
[   29.441257][    C0] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[   29.441534][    C0] Workqueue: netns cleanup_net
[   29.441666][    C0] Call Trace:
[   29.441779][    C0]  <IRQ>
[ 29.441855][ C0] dump_stack_lvl (lib/dump_stack.c:122) 
[ 29.441997][ C0] do_raw_spin_unlock (kernel/locking/spinlock_debug.c:100 kernel/locking/spinlock_debug.c:141) 
[ 29.442138][ C0] _raw_spin_unlock (./arch/x86/include/asm/preempt.h:94 ./include/linux/spinlock_api_smp.h:143 kernel/locking/spinlock.c:186) 
[ 29.442274][ C0] 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) 
[ 29.442407][ C0] handle_softirqs (kernel/softirq.c:554) 
[ 29.442571][ C0] ? 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) 
[ 29.442705][ C0] do_softirq (kernel/softirq.c:455 kernel/softirq.c:442) 
[   29.442816][    C0]  </IRQ>
[   29.442881][    C0]  <TASK>
[ 29.442955][ C0] __local_bh_enable_ip (kernel/softirq.c:382) 
[ 29.443082][ C0] dev_deactivate_many (net/sched/sch_generic.c:1356) 
[ 29.443224][ C0] __dev_close_many (net/core/dev.c:1547) 
[ 29.443358][ C0] ? __pfx___dev_close_many (net/core/dev.c:1522) 
[ 29.443509][ C0] ? __pfx_validate_chain (kernel/locking/lockdep.c:3824) 
[ 29.443637][ C0] ? __pfx_validate_chain (kernel/locking/lockdep.c:3824) 
[ 29.443763][ C0] dev_close_many (net/core/dev.c:1585) 
[ 29.443907][ C0] ? __pfx_dev_close_many (net/core/dev.c:1575) 
[ 29.444038][ C0] unregister_netdevice_many_notify (net/core/dev.c:11321) 
[ 29.444208][ C0] ? __lock_release (kernel/locking/lockdep.c:5435) 
[ 29.444341][ C0] ? net_generic (./include/linux/rcupdate.h:336 ./include/linux/rcupdate.h:869 ./include/net/netns/generic.h:48) 
[ 29.444496][ C0] ? __pfx_unregister_netdevice_many_notify (net/core/dev.c:11288) 
[ 29.444655][ C0] ? rtnl_is_locked (net/core/rtnetlink.c:164) 
[ 29.444780][ C0] ? unregister_netdevice_queue (net/core/dev.c:11273) 
[ 29.444933][ C0] ? __pfx_unregister_netdevice_queue (net/core/dev.c:11272) 
[ 29.445094][ C0] ? net_generic (./include/linux/rcupdate.h:336 ./include/linux/rcupdate.h:869 ./include/net/netns/generic.h:48) 
[ 29.445217][ C0] ? mutex_is_locked (./arch/x86/include/asm/atomic64_64.h:15 ./include/linux/atomic/atomic-arch-fallback.h:2583 ./include/linux/atomic/atomic-long.h:38 ./include/linux/atomic/atomic-instrumented.h:3189 kernel/locking/mutex.c:81 kernel/locking/mutex.c:91) 
[ 29.445345][ C0] ? nexthop_net_exit_batch_rtnl (net/ipv4/nexthop.c:585 net/ipv4/nexthop.c:2146 net/ipv4/nexthop.c:2654 net/ipv4/nexthop.c:4004) 
[ 29.445510][ C0] cleanup_net (net/core/net_namespace.c:622) 
[ 29.445637][ C0] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5724) 
[ 29.445761][ C0] ? __pfx_cleanup_net (net/core/net_namespace.c:570) 
[ 29.445890][ C0] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 52)) 
[ 29.446014][ C0] ? process_one_work (kernel/workqueue.c:3207) 
[ 29.446138][ C0] ? lock_acquire (kernel/locking/lockdep.c:5732) 
[ 29.446263][ C0] ? process_one_work (kernel/workqueue.c:3207) 
[ 29.446400][ C0] process_one_work (kernel/workqueue.c:3231) 
[ 29.446535][ C0] ? __pfx___lock_release (kernel/locking/lockdep.c:5411) 
[ 29.446662][ C0] ? __pfx_process_one_work (kernel/workqueue.c:3133) 
[ 29.446799][ C0] ? assign_work (kernel/workqueue.c:1202) 
[ 29.446925][ C0] worker_thread (kernel/workqueue.c:3306 kernel/workqueue.c:3390) 
[ 29.447061][ C0] ? __pfx_worker_thread (kernel/workqueue.c:3339) 
[ 29.447188][ C0] kthread (kernel/kthread.c:389) 
[ 29.447290][ C0] ? __pfx_kthread (kernel/kthread.c:342) 
[ 29.447427][ C0] ret_from_fork (arch/x86/kernel/process.c:147) 
[ 29.447584][ C0] ? __pfx_kthread (kernel/kthread.c:342) 


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