======================================
| [ 18.171805][ T11] #3: ffffffff86607e88 (rtnl_mutex){+.+.}-{4:4}, at: default_device_exit_batch (net/core/dev.c:12103)
| [ 18.172087][ T11] #4: ffffffff865f6a70 ((netdev_chain).rwsem){++++}-{4:4}, at: blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
| [   18.172365][   T11]
| [   18.172365][   T11] stack backtrace:
[   18.172783][   T11] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   18.172958][   T11] Workqueue: netns cleanup_net
[   18.173104][   T11] Call Trace:
[   18.173210][   T11]  <TASK>
[ 18.173283][ T11] dump_stack_lvl (lib/dump_stack.c:123)
[ 18.173430][ T11] print_deadlock_bug (kernel/locking/lockdep.c:3040)
[ 18.173570][ T11] validate_chain (kernel/locking/lockdep.c:3894)
[ 18.173711][ T11] ? __pfx_validate_chain (kernel/locking/lockdep.c:3860)
[ 18.173851][ 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)
[ 18.173990][ T11] ? mark_lock (kernel/locking/lockdep.c:4727 (discriminator 3))
[ 18.174095][ T11] __lock_acquire (kernel/locking/lockdep.c:5226)
[ 18.174241][ T11] lock_acquire.part.0 (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:5851)
[ 18.174382][ T11] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 18.174558][ T11] ? __lock_acquire (kernel/locking/lockdep.c:5226)
[ 18.174700][ T11] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5814)
[ 18.174840][ T11] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 37))
[ 18.174983][ T11] ? lock_acquire (kernel/locking/lockdep.c:5822)
[ 18.175125][ T11] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 18.175303][ 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)
[ 18.175410][ T11] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 18.175582][ T11] ? __pfx_down_read (kernel/locking/rwsem.c:1522)
[ 18.175721][ T11] ? __lock_release (kernel/locking/lockdep.c:5525)
[ 18.175858][ T11] blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 18.176009][ T11] __netdev_upper_dev_unlink (net/core/dev.c:8000 (discriminator 11) net/core/dev.c:8017 (discriminator 11) net/core/dev.c:8167 (discriminator 11))
[ 18.176150][ T11] ? mark_held_locks (kernel/locking/lockdep.c:4321)
[ 18.176292][ T11] ? __pfx___netdev_upper_dev_unlink (net/core/dev.c:8151)
[ 18.176470][ T11] ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:4347 kernel/locking/lockdep.c:4406)
[ 18.176705][ T11] ? __try_to_del_timer_sync (kernel/time/timer.c:1498)
[ 18.176849][ T11] ? __pfx___try_to_del_timer_sync (kernel/time/timer.c:1498)
[ 18.177018][ T11] ? mark_held_locks (kernel/locking/lockdep.c:4321)
[ 18.177160][ T11] netdev_upper_dev_unlink (net/core/dev.c:8190)
[ 18.177303][ T11] ? __pfx_netdev_upper_dev_unlink (net/core/dev.c:8190)
[ 18.177478][ 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)
[ 18.177629][ T11] ? rtnl_is_locked (net/core/rtnetlink.c:164)
[ 18.177769][ T11] ? netdev_master_upper_dev_get (net/core/dev.c:7230)
[ 18.177941][ T11] vrf_device_event (drivers/net/vrf.c:1110 drivers/net/vrf.c:1119 drivers/net/vrf.c:1804)
[ 18.178086][ T11] notifier_call_chain (kernel/notifier.c:85 (discriminator 2))
[ 18.178233][ T11] blocking_notifier_call_chain (kernel/notifier.c:381 kernel/notifier.c:368)
[ 18.178372][ T11] unregister_netdevice_many_notify (net/core/dev.c:11571)
[ 18.178548][ T11] ? __pfx_unregister_netdevice_many_notify (net/core/dev.c:11512)
[ 18.178722][ T11] ? default_device_exit_batch (net/core/dev.c:12103)
[ 18.178860][ T11] ? rtnl_is_locked (net/core/rtnetlink.c:164)
[ 18.178997][ T11] ? unregister_netdevice_queue (net/core/dev.c:11497)
[ 18.179169][ T11] ? __pfx_unregister_netdevice_queue (net/core/dev.c:11496)
[ 18.179342][ T11] ? __pfx_unregister_netdevice_queue (net/core/dev.c:11496)
[ 18.179512][ T11] default_device_exit_batch (net/core/dev.c:12117)
[ 18.179652][ T11] ? __pfx_default_device_exit_batch (net/core/dev.c:12092)
[ 18.179825][ T11] ? ops_exit_list (net/core/net_namespace.c:171 (discriminator 3))
[ 18.179965][ T11] cleanup_net (net/core/net_namespace.c:647 (discriminator 3))
[ 18.180102][ T11] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5814)
[ 18.180241][ T11] ? __pfx_cleanup_net (net/core/net_namespace.c:592)
[ 18.180377][ T11] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 37))
[ 18.180517][ T11] ? lock_acquire (kernel/locking/lockdep.c:5822)
[ 18.180653][ T11] ? process_one_work (kernel/workqueue.c:3205)
[ 18.180801][ T11] process_one_work (kernel/workqueue.c:3229)
[ 18.180945][ T11] ? __pfx___lock_release (kernel/locking/lockdep.c:5501)
[ 18.181085][ T11] ? __pfx_process_one_work (kernel/workqueue.c:3131)
[ 18.181221][ T11] ? assign_work (kernel/workqueue.c:1200)
[ 18.181363][ T11] worker_thread (kernel/workqueue.c:3304 kernel/workqueue.c:3391)
[ 18.181508][ T11] ? __pfx_worker_thread (kernel/workqueue.c:3337)
[ 18.181647][ T11] kthread (kernel/kthread.c:389)
[ 18.181759][ T11] ? __pfx_kthread (kernel/kthread.c:342)
[ 18.181907][ T11] ret_from_fork (arch/x86/kernel/process.c:147)
[ 18.182049][ T11] ? __pfx_kthread (kernel/kthread.c:342)


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