======================================
| [ 209.043779][ T11] #3: ffffffffa3607e88 (rtnl_mutex){+.+.}-{4:4}, at: default_device_exit_batch (net/core/dev.c:12103)
| [ 209.044065][ T11] #4: ffffffffa35f6a70 ((netdev_chain).rwsem){++++}-{4:4}, at: blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
| [  209.044339][   T11]
| [  209.044339][   T11] stack backtrace:
[  209.044750][   T11] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  209.044935][   T11] Workqueue: netns cleanup_net
[  209.045079][   T11] Call Trace:
[  209.045188][   T11]  <TASK>
[ 209.045262][ T11] dump_stack_lvl (lib/dump_stack.c:123)
[ 209.045405][ T11] print_deadlock_bug (kernel/locking/lockdep.c:3040)
[ 209.045546][ T11] validate_chain (kernel/locking/lockdep.c:3894)
[ 209.045684][ T11] ? __pfx_validate_chain (kernel/locking/lockdep.c:3860)
[ 209.045821][ 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)
[ 209.045961][ T11] ? mark_lock (kernel/locking/lockdep.c:4727 (discriminator 3))
[ 209.046070][ T11] __lock_acquire (kernel/locking/lockdep.c:5226)
[ 209.046223][ T11] lock_acquire.part.0 (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:5851)
[ 209.046370][ T11] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 209.046555][ T11] ? __lock_acquire (kernel/locking/lockdep.c:5226)
[ 209.046703][ T11] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5814)
[ 209.046855][ T11] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 37))
[ 209.047012][ T11] ? lock_acquire (kernel/locking/lockdep.c:5822)
[ 209.047170][ T11] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 209.047359][ 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)
[ 209.047474][ T11] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 209.047661][ T11] ? __pfx_down_read (kernel/locking/rwsem.c:1522)
[ 209.047811][ T11] ? __lock_release (kernel/locking/lockdep.c:5525)
[ 209.047969][ T11] blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 209.048126][ 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))
[ 209.048285][ T11] ? mark_held_locks (kernel/locking/lockdep.c:4321)
[ 209.048440][ T11] ? __pfx___netdev_upper_dev_unlink (net/core/dev.c:8151)
[ 209.048629][ T11] ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:4347 kernel/locking/lockdep.c:4406)
[ 209.048856][ T11] ? __try_to_del_timer_sync (kernel/time/timer.c:1498)
[ 209.049014][ T11] ? __pfx___try_to_del_timer_sync (kernel/time/timer.c:1498)
[ 209.049214][ T11] ? mark_held_locks (kernel/locking/lockdep.c:4321)
[ 209.049374][ T11] netdev_upper_dev_unlink (net/core/dev.c:8190)
[ 209.049528][ T11] ? __pfx_netdev_upper_dev_unlink (net/core/dev.c:8190)
[ 209.049716][ 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)
[ 209.049869][ T11] ? rtnl_is_locked (net/core/rtnetlink.c:164)
[ 209.050022][ T11] ? netdev_master_upper_dev_get (net/core/dev.c:7230)
[ 209.050215][ T11] vrf_device_event (drivers/net/vrf.c:1110 drivers/net/vrf.c:1119 drivers/net/vrf.c:1804)
[ 209.050369][ T11] notifier_call_chain (kernel/notifier.c:85 (discriminator 2))
[ 209.050524][ T11] blocking_notifier_call_chain (kernel/notifier.c:381 kernel/notifier.c:368)
[ 209.050681][ T11] unregister_netdevice_many_notify (net/core/dev.c:11571)
[ 209.050875][ T11] ? __pfx_unregister_netdevice_many_notify (net/core/dev.c:11512)
[ 209.051064][ T11] ? default_device_exit_batch (net/core/dev.c:12103)
[ 209.051214][ T11] ? rtnl_is_locked (net/core/rtnetlink.c:164)
[ 209.051366][ T11] ? unregister_netdevice_queue (net/core/dev.c:11497)
[ 209.051553][ T11] ? __pfx_unregister_netdevice_queue (net/core/dev.c:11496)
[ 209.051752][ T11] ? __pfx_unregister_netdevice_queue (net/core/dev.c:11496)
[ 209.051939][ T11] default_device_exit_batch (net/core/dev.c:12117)
[ 209.052092][ T11] ? __pfx_default_device_exit_batch (net/core/dev.c:12092)
[ 209.052271][ T11] ? ops_exit_list (net/core/net_namespace.c:171 (discriminator 3))
[ 209.052416][ T11] cleanup_net (net/core/net_namespace.c:647 (discriminator 3))
[ 209.052550][ T11] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5814)
[ 209.052688][ T11] ? __pfx_cleanup_net (net/core/net_namespace.c:592)
[ 209.052830][ T11] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 37))
[ 209.052967][ T11] ? lock_acquire (kernel/locking/lockdep.c:5822)
[ 209.053104][ T11] ? process_one_work (kernel/workqueue.c:3205)
[ 209.053244][ T11] process_one_work (kernel/workqueue.c:3229)
[ 209.053386][ T11] ? __pfx___lock_release (kernel/locking/lockdep.c:5501)
[ 209.053526][ T11] ? __pfx_process_one_work (kernel/workqueue.c:3131)
[ 209.053665][ T11] ? assign_work (kernel/workqueue.c:1200)
[ 209.053809][ T11] worker_thread (kernel/workqueue.c:3304 kernel/workqueue.c:3391)
[ 209.053954][ T11] ? __pfx_worker_thread (kernel/workqueue.c:3337)
[ 209.054093][ T11] kthread (kernel/kthread.c:389)
[ 209.054202][ T11] ? __pfx_kthread (kernel/kthread.c:342)
[ 209.054342][ T11] ret_from_fork (arch/x86/kernel/process.c:147)
[ 209.054486][ T11] ? __pfx_kthread (kernel/kthread.c:342)


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