======================================
| [ 17.968881][ T11] #3: ffffffff8cc07e88 (rtnl_mutex){+.+.}-{4:4}, at: default_device_exit_batch (net/core/dev.c:12109)
| [ 17.969176][ T11] #4: ffffffff8cbf6a70 ((netdev_chain).rwsem){++++}-{4:4}, at: blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
| [   17.969473][   T11]
| [   17.969473][   T11] stack backtrace:
[   17.969903][   T11] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   17.970093][   T11] Workqueue: netns cleanup_net
[   17.970254][   T11] Call Trace:
[   17.970365][   T11]  <TASK>
[ 17.970443][ T11] dump_stack_lvl (lib/dump_stack.c:123)
[ 17.970607][ T11] print_deadlock_bug (kernel/locking/lockdep.c:3040)
[ 17.970763][ T11] validate_chain (kernel/locking/lockdep.c:3894)
[ 17.970916][ T11] ? __pfx_validate_chain (kernel/locking/lockdep.c:3860)
[ 17.971072][ 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)
[ 17.971220][ T11] ? mark_lock (kernel/locking/lockdep.c:4727 (discriminator 3))
[ 17.971334][ T11] __lock_acquire (kernel/locking/lockdep.c:5226)
[ 17.971485][ T11] lock_acquire.part.0 (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:5851)
[ 17.971631][ T11] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 17.971812][ T11] ? __lock_acquire (kernel/locking/lockdep.c:5226)
[ 17.971962][ T11] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5814)
[ 17.972111][ T11] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 37))
[ 17.972261][ T11] ? lock_acquire (kernel/locking/lockdep.c:5822)
[ 17.972407][ T11] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 17.972591][ 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)
[ 17.972706][ T11] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 17.972892][ T11] ? __pfx_down_read (kernel/locking/rwsem.c:1522)
[ 17.973040][ T11] ? __lock_release (kernel/locking/lockdep.c:5525)
[ 17.973189][ T11] blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 17.973336][ 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))
[ 17.973484][ T11] ? mark_held_locks (kernel/locking/lockdep.c:4321)
[ 17.973635][ T11] ? __pfx___netdev_upper_dev_unlink (net/core/dev.c:8151)
[ 17.973820][ T11] ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:4347 kernel/locking/lockdep.c:4406)
[ 17.974005][ T11] ? __try_to_del_timer_sync (kernel/time/timer.c:1498)
[ 17.974155][ T11] ? __pfx___try_to_del_timer_sync (kernel/time/timer.c:1498)
[ 17.974338][ T11] ? mark_held_locks (kernel/locking/lockdep.c:4321)
[ 17.974489][ T11] netdev_upper_dev_unlink (net/core/dev.c:8190)
[ 17.974634][ T11] ? __pfx_netdev_upper_dev_unlink (net/core/dev.c:8190)
[ 17.974819][ 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)
[ 17.974966][ T11] ? rtnl_is_locked (net/core/rtnetlink.c:163)
[ 17.975119][ T11] ? netdev_master_upper_dev_get (net/core/dev.c:7230)
[ 17.975302][ T11] vrf_device_event (drivers/net/vrf.c:1110 drivers/net/vrf.c:1119 drivers/net/vrf.c:1804)
[ 17.975451][ T11] notifier_call_chain (kernel/notifier.c:85 (discriminator 2))
[ 17.975604][ T11] blocking_notifier_call_chain (kernel/notifier.c:381 kernel/notifier.c:368)
[ 17.975756][ T11] unregister_netdevice_many_notify (net/core/dev.c:11575)
[ 17.975944][ T11] ? __pfx_unregister_netdevice_many_notify (net/core/dev.c:11516)
[ 17.976128][ T11] ? default_device_exit_batch (net/core/dev.c:12109)
[ 17.976280][ T11] ? rtnl_is_locked (net/core/rtnetlink.c:163)
[ 17.976427][ T11] ? unregister_netdevice_queue (net/core/dev.c:11501)
[ 17.976618][ T11] ? __pfx_unregister_netdevice_queue (net/core/dev.c:11500)
[ 17.976808][ T11] ? __pfx_unregister_netdevice_queue (net/core/dev.c:11500)
[ 17.976999][ T11] default_device_exit_batch (net/core/dev.c:12123)
[ 17.977150][ T11] ? __pfx_default_device_exit_batch (net/core/dev.c:12098)
[ 17.977339][ T11] ? ops_exit_list (net/core/net_namespace.c:171 (discriminator 3))
[ 17.977490][ T11] cleanup_net (net/core/net_namespace.c:647 (discriminator 3))
[ 17.977638][ T11] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5814)
[ 17.977791][ T11] ? __pfx_cleanup_net (net/core/net_namespace.c:592)
[ 17.977935][ T11] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 37))
[ 17.978084][ T11] ? lock_acquire (kernel/locking/lockdep.c:5822)
[ 17.978234][ T11] ? process_one_work (kernel/workqueue.c:3205)
[ 17.978381][ T11] process_one_work (kernel/workqueue.c:3229)
[ 17.978533][ T11] ? __pfx___lock_release (kernel/locking/lockdep.c:5501)
[ 17.978682][ T11] ? __pfx_process_one_work (kernel/workqueue.c:3131)
[ 17.978841][ T11] ? assign_work (kernel/workqueue.c:1200)
[ 17.978993][ T11] worker_thread (kernel/workqueue.c:3304 kernel/workqueue.c:3391)
[ 17.979149][ T11] ? __pfx_worker_thread (kernel/workqueue.c:3337)
[ 17.979299][ T11] kthread (kernel/kthread.c:389)
[ 17.979416][ T11] ? __pfx_kthread (kernel/kthread.c:342)
[ 17.979566][ T11] ret_from_fork (arch/x86/kernel/process.c:147)
[ 17.979720][ T11] ? __pfx_kthread (kernel/kthread.c:342)


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