======================================
| [ 50.242532][ T11] #3: ffffffffb9de7a48 (rtnl_mutex){+.+.}-{4:4}, at: cleanup_net (net/core/net_namespace.c:639)
| [ 50.242821][ T11] #4: ffffffffb9dd6630 ((netdev_chain).rwsem){++++}-{4:4}, at: blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
| [   50.243147][   T11]
| [   50.243147][   T11] stack backtrace:
[   50.243686][   T11] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   50.243870][   T11] Workqueue: netns cleanup_net
[   50.244050][   T11] Call Trace:
[   50.244169][   T11]  <TASK>
[ 50.244285][ T11] dump_stack_lvl (lib/dump_stack.c:123)
[ 50.244442][ T11] print_deadlock_bug (kernel/locking/lockdep.c:3040)
[ 50.244639][ T11] validate_chain (kernel/locking/lockdep.c:3894)
[ 50.244831][ T11] ? __pfx_validate_chain (kernel/locking/lockdep.c:3860)
[ 50.244978][ T11] ? hlock_class (./arch/x86/include/asm/bitops.h:227 ./arch/x86/include/asm/bitops.h:239 ./include/asm-generic/bitops/instrumented-non-atomic.h:142 kernel/locking/lockdep.c:228)
[ 50.245154][ T11] ? mark_lock (kernel/locking/lockdep.c:4727 (discriminator 3))
[ 50.245277][ T11] __lock_acquire (kernel/locking/lockdep.c:5226)
[ 50.245462][ T11] ? spin_bug (kernel/locking/spinlock_debug.c:57 kernel/locking/spinlock_debug.c:78)
[ 50.245574][ T11] ? debug_object_assert_init (./include/linux/err.h:81 lib/debugobjects.c:1010)
[ 50.245756][ T11] lock_acquire.part.0 (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:5851)
[ 50.245901][ T11] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 50.246129][ T11] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5814)
[ 50.246300][ T11] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 37))
[ 50.246456][ T11] ? lock_acquire (kernel/locking/lockdep.c:5822)
[ 50.246635][ T11] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 50.246817][ T11] down_read (./arch/x86/include/asm/preempt.h:79 kernel/locking/rwsem.c:1246 kernel/locking/rwsem.c:1261 kernel/locking/rwsem.c:1526)
[ 50.246960][ T11] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 50.247165][ T11] ? __pfx_down_read (kernel/locking/rwsem.c:1522)
[ 50.247339][ T11] blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 50.247519][ T11] __dev_close_many (net/core/dev.c:1537 (discriminator 3))
[ 50.247680][ T11] ? __pfx___dev_close_many (net/core/dev.c:1525)
[ 50.247826][ T11] dev_close_many (net/core/dev.c:1588)
[ 50.247976][ T11] ? __lock_release (kernel/locking/lockdep.c:5525)
[ 50.248123][ T11] ? __pfx_dev_close_many (net/core/dev.c:1578)
[ 50.248272][ T11] ? __pfx___lock_release (kernel/locking/lockdep.c:5501)
[ 50.248433][ T11] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5814)
[ 50.248597][ T11] vlan_device_event (net/8021q/vlan.c:451) 8021q
[ 50.248785][ T11] ? net_generic (./include/net/netns/generic.h:51) vxlan
[ 50.248946][ T11] ? __pfx_vlan_device_event (net/8021q/vlan.c:362) 8021q
[ 50.249123][ T11] ? __pfx_vxlan_netdevice_event (drivers/net/vxlan/vxlan_core.c:4737) vxlan
[ 50.249321][ T11] ? packet_notifier (net/packet/af_packet.c:4282)
[ 50.249472][ T11] notifier_call_chain (kernel/notifier.c:85 (discriminator 2))
[ 50.249615][ T11] blocking_notifier_call_chain (kernel/notifier.c:381 kernel/notifier.c:368)
[ 50.249771][ T11] dev_close_many (net/core/dev.c:1591)
[ 50.249919][ T11] ? __lock_release (kernel/locking/lockdep.c:5525)
[ 50.250057][ T11] ? __virt_addr_valid (./include/linux/rcupdate.h:347 ./include/linux/rcupdate.h:962 ./include/linux/mmzone.h:2058 arch/x86/mm/physaddr.c:65)
[ 50.250205][ T11] ? __pfx_dev_close_many (net/core/dev.c:1578)
[ 50.250364][ T11] unregister_netdevice_many_notify (net/core/dev.c:11549)
[ 50.250552][ T11] ? __pfx_unregister_netdevice_many_notify (net/core/dev.c:11516)
[ 50.250724][ T11] ? mark_held_locks (kernel/locking/lockdep.c:4321)
[ 50.250883][ T11] ? 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.h:47 kernel/locking/mutex.c:66)
[ 50.251026][ T11] ? nexthop_net_exit_batch_rtnl (net/ipv4/nexthop.c:585 net/ipv4/nexthop.c:2158 net/ipv4/nexthop.c:2666 net/ipv4/nexthop.c:4010)
[ 50.251211][ T11] cleanup_net (net/core/net_namespace.c:644)
[ 50.251373][ T11] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5814)
[ 50.251517][ T11] ? __pfx_cleanup_net (net/core/net_namespace.c:592)
[ 50.251657][ T11] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 37))
[ 50.251795][ T11] ? lock_acquire (kernel/locking/lockdep.c:5822)
[ 50.251951][ T11] ? process_one_work (kernel/workqueue.c:3205)
[ 50.252094][ T11] process_one_work (kernel/workqueue.c:3229)
[ 50.252249][ T11] ? __pfx___lock_release (kernel/locking/lockdep.c:5501)
[ 50.252401][ T11] ? __pfx_process_one_work (kernel/workqueue.c:3131)
[ 50.252545][ T11] ? assign_work (kernel/workqueue.c:1200)
[ 50.252695][ T11] worker_thread (kernel/workqueue.c:3304 kernel/workqueue.c:3391)
[ 50.252841][ T11] ? __pfx_worker_thread (kernel/workqueue.c:3337)
[ 50.252990][ T11] kthread (kernel/kthread.c:389)
[ 50.253104][ T11] ? __pfx_kthread (kernel/kthread.c:342)
[ 50.253250][ T11] ret_from_fork (arch/x86/kernel/process.c:147)
[ 50.253404][ T11] ? __pfx_kthread (kernel/kthread.c:342)


Finger prints:
print_deadlock_bug:validate_chain:__lock_acquire:down_read:blocking_notifier_call_chain