======================================
| [ 155.106173][ T66] #3: ffffffffb2807e88 (rtnl_mutex){+.+.}-{4:4}, at: cleanup_net (net/core/net_namespace.c:639)
| [ 155.106422][ T66] #4: ffffffffb27f6a70 ((netdev_chain).rwsem){++++}-{4:4}, at: blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
| [  155.106703][   T66]
| [  155.106703][   T66] stack backtrace:
[  155.107121][   T66] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  155.107297][   T66] Workqueue: netns cleanup_net
[  155.107442][   T66] Call Trace:
[  155.107552][   T66]  <TASK>
[ 155.107631][ T66] dump_stack_lvl (lib/dump_stack.c:123)
[ 155.107781][ T66] print_deadlock_bug (kernel/locking/lockdep.c:3040)
[ 155.107926][ T66] validate_chain (kernel/locking/lockdep.c:3894)
[ 155.108069][ T66] ? __pfx_validate_chain (kernel/locking/lockdep.c:3860)
[ 155.108211][ T66] ? 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)
[ 155.108348][ T66] ? mark_lock (kernel/locking/lockdep.c:4727 (discriminator 3))
[ 155.108458][ T66] __lock_acquire (kernel/locking/lockdep.c:5226)
[ 155.108602][ T66] lock_acquire.part.0 (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:5851)
[ 155.108738][ T66] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 155.108910][ T66] ? __lock_acquire (kernel/locking/lockdep.c:5226)
[ 155.109044][ T66] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5814)
[ 155.109182][ T66] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 37))
[ 155.109321][ T66] ? lock_acquire (kernel/locking/lockdep.c:5822)
[ 155.109456][ T66] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 155.109630][ T66] down_read (./arch/x86/include/asm/preempt.h:79 kernel/locking/rwsem.c:1246 kernel/locking/rwsem.c:1261 kernel/locking/rwsem.c:1526)
[ 155.109736][ T66] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 155.109907][ T66] ? __pfx_down_read (kernel/locking/rwsem.c:1522)
[ 155.110044][ T66] ? __lock_release (kernel/locking/lockdep.c:5525)
[ 155.110184][ T66] blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 155.110321][ T66] __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))
[ 155.110460][ T66] ? mark_held_locks (kernel/locking/lockdep.c:4321)
[ 155.110602][ T66] ? __pfx___netdev_upper_dev_unlink (net/core/dev.c:8151)
[ 155.110773][ T66] ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:4347 kernel/locking/lockdep.c:4406)
[ 155.110942][ T66] ? __try_to_del_timer_sync (kernel/time/timer.c:1498)
[ 155.111083][ T66] ? __pfx___try_to_del_timer_sync (kernel/time/timer.c:1498)
[ 155.111253][ T66] ? mark_held_locks (kernel/locking/lockdep.c:4321)
[ 155.111394][ T66] netdev_upper_dev_unlink (net/core/dev.c:8190)
[ 155.111532][ T66] ? __pfx_netdev_upper_dev_unlink (net/core/dev.c:8190)
[ 155.111704][ T66] ? 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)
[ 155.111841][ T66] ? rtnl_is_locked (net/core/rtnetlink.c:163)
[ 155.111980][ T66] ? netdev_master_upper_dev_get (net/core/dev.c:7230)
[ 155.112151][ T66] vrf_device_event (drivers/net/vrf.c:1110 drivers/net/vrf.c:1119 drivers/net/vrf.c:1804)
[ 155.112289][ T66] notifier_call_chain (kernel/notifier.c:85 (discriminator 2))
[ 155.112428][ T66] blocking_notifier_call_chain (kernel/notifier.c:381 kernel/notifier.c:368)
[ 155.112564][ T66] unregister_netdevice_many_notify (net/core/dev.c:11575)
[ 155.112738][ T66] ? mark_held_locks (kernel/locking/lockdep.c:4321)
[ 155.112874][ T66] ? __pfx_unregister_netdevice_many_notify (net/core/dev.c:11516)
[ 155.113042][ T66] ? 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)
[ 155.113179][ T66] ? rtnl_is_locked (net/core/rtnetlink.c:163)
[ 155.113318][ T66] ? 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)
[ 155.113453][ T66] ? 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)
[ 155.113632][ T66] cleanup_net (net/core/net_namespace.c:644)
[ 155.113772][ T66] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5814)
[ 155.113910][ T66] ? __pfx_cleanup_net (net/core/net_namespace.c:592)
[ 155.114046][ T66] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 37))
[ 155.114183][ T66] ? lock_acquire (kernel/locking/lockdep.c:5822)
[ 155.114319][ T66] ? process_one_work (kernel/workqueue.c:3205)
[ 155.114457][ T66] process_one_work (kernel/workqueue.c:3229)
[ 155.114597][ T66] ? __pfx___lock_release (kernel/locking/lockdep.c:5501)
[ 155.114736][ T66] ? __pfx_process_one_work (kernel/workqueue.c:3131)
[ 155.114877][ T66] ? assign_work (kernel/workqueue.c:1200)
[ 155.115016][ T66] worker_thread (kernel/workqueue.c:3304 kernel/workqueue.c:3391)
[ 155.115157][ T66] ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:4347 kernel/locking/lockdep.c:4406)
[ 155.115330][ T66] ? __pfx_worker_thread (kernel/workqueue.c:3337)
[ 155.115470][ T66] ? __pfx_worker_thread (kernel/workqueue.c:3337)
[ 155.115607][ T66] kthread (kernel/kthread.c:389)
[ 155.115717][ T66] ? __pfx_kthread (kernel/kthread.c:342)
[ 155.115858][ T66] ret_from_fork (arch/x86/kernel/process.c:147)
[ 155.116000][ T66] ? __pfx_kthread (kernel/kthread.c:342)


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