======================================
| [ 953.722410][ T67] #3: ffffffffbbe07e88 (rtnl_mutex){+.+.}-{4:4}, at: default_device_exit_batch (net/core/dev.c:12109)
| [ 953.722793][ T67] #4: ffffffffbbdf6a70 ((netdev_chain).rwsem){++++}-{4:4}, at: blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
| [  953.723123][   T67]
| [  953.723123][   T67] stack backtrace:
[  953.723671][   T67] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  953.723873][   T67] Workqueue: netns cleanup_net
[  953.724043][   T67] Call Trace:
[  953.724169][   T67]  <TASK>
[ 953.724299][ T67] dump_stack_lvl (lib/dump_stack.c:123)
[ 953.724485][ T67] print_deadlock_bug (kernel/locking/lockdep.c:3040)
[ 953.724654][ T67] validate_chain (kernel/locking/lockdep.c:3894)
[ 953.724865][ T67] ? __lock_acquire (kernel/locking/lockdep.c:5226)
[ 953.725032][ T67] ? __pfx_validate_chain (kernel/locking/lockdep.c:3860)
[ 953.725243][ T67] ? 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)
[ 953.725415][ T67] ? mark_lock (kernel/locking/lockdep.c:4727 (discriminator 3))
[ 953.725538][ T67] __lock_acquire (kernel/locking/lockdep.c:5226)
[ 953.725744][ T67] lock_acquire.part.0 (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:5851)
[ 953.725914][ T67] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 953.726136][ T67] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5814)
[ 953.726286][ T67] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 37))
[ 953.726529][ T67] ? lock_acquire (kernel/locking/lockdep.c:5822)
[ 953.726683][ T67] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 953.726889][ T67] down_read (./arch/x86/include/asm/preempt.h:79 kernel/locking/rwsem.c:1246 kernel/locking/rwsem.c:1261 kernel/locking/rwsem.c:1526)
[ 953.727051][ T67] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 953.727246][ T67] ? __pfx_down_read (kernel/locking/rwsem.c:1522)
[ 953.727446][ T67] ? __mutex_unlock_slowpath (./arch/x86/include/asm/atomic64_64.h:101 ./include/linux/atomic/atomic-arch-fallback.h:4329 ./include/linux/atomic/atomic-long.h:1506 ./include/linux/atomic/atomic-instrumented.h:4481 kernel/locking/mutex.c:913)
[ 953.727630][ T67] blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 953.727784][ T67] __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))
[ 953.727939][ T67] ? __pfx___netdev_upper_dev_unlink (net/core/dev.c:8151)
[ 953.728171][ T67] ? synchronize_rcu_expedited (kernel/rcu/tree_exp.h:995 (discriminator 1))
[ 953.728371][ T67] ? __pfx_autoremove_wake_function (kernel/sched/wait.c:383)
[ 953.728615][ T67] ? __pfx___mutex_unlock_slowpath (kernel/locking/mutex.c:890)
[ 953.728809][ T67] netdev_upper_dev_unlink (net/core/dev.c:8190)
[ 953.728990][ T67] ? __pfx_netdev_upper_dev_unlink (net/core/dev.c:8190)
[ 953.729199][ T67] ? 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)
[ 953.729353][ T67] ? rtnl_is_locked (net/core/rtnetlink.c:163)
[ 953.729571][ T67] ? netdev_master_upper_dev_get (net/core/dev.c:7230)
[ 953.729753][ T67] ovs_netdev_detach_dev (net/openvswitch/vport-netdev.c:158 (discriminator 11)) openvswitch
[ 953.729967][ T67] ? ovs_netdev_get_vport (net/openvswitch/vport-netdev.c:196 (discriminator 3)) openvswitch
[ 953.730213][ T67] dp_device_event (net/openvswitch/dp_notify.c:77) openvswitch
[ 953.730437][ T67] ? trace_notifier_run (./include/trace/events/notifier.h:59 (discriminator 37))
[ 953.730593][ T67] notifier_call_chain (kernel/notifier.c:85 (discriminator 2))
[ 953.730748][ T67] blocking_notifier_call_chain (kernel/notifier.c:381 kernel/notifier.c:368)
[ 953.730970][ T67] unregister_netdevice_many_notify (net/core/dev.c:11575)
[ 953.731160][ T67] ? __pfx_unregister_netdevice_many_notify (net/core/dev.c:11516)
[ 953.731342][ T67] ? default_device_exit_batch (net/core/dev.c:12109)
[ 953.731593][ T67] ? rtnl_is_locked (net/core/rtnetlink.c:163)
[ 953.731740][ T67] ? unregister_netdevice_queue (net/core/dev.c:11501)
[ 953.731919][ T67] ? __pfx_unregister_netdevice_queue (net/core/dev.c:11500)
[ 953.732098][ T67] ? __pfx_unregister_netdevice_queue (net/core/dev.c:11500)
[ 953.732277][ T67] default_device_exit_batch (net/core/dev.c:12123)
[ 953.732522][ T67] ? __pfx_default_device_exit_batch (net/core/dev.c:12098)
[ 953.732702][ T67] ? ops_exit_list (net/core/net_namespace.c:171 (discriminator 3))
[ 953.732874][ T67] cleanup_net (net/core/net_namespace.c:647 (discriminator 3))
[ 953.733055][ T67] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5814)
[ 953.733201][ T67] ? __pfx_cleanup_net (net/core/net_namespace.c:592)
[ 953.733440][ T67] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 37))
[ 953.733591][ T67] ? lock_acquire (kernel/locking/lockdep.c:5822)
[ 953.733791][ T67] ? process_one_work (kernel/workqueue.c:3205)
[ 953.733935][ T67] process_one_work (kernel/workqueue.c:3229)
[ 953.734081][ T67] ? __pfx___lock_release (kernel/locking/lockdep.c:5501)
[ 953.734230][ T67] ? __pfx_process_one_work (kernel/workqueue.c:3131)
[ 953.734408][ T67] ? assign_work (kernel/workqueue.c:1200)
[ 953.734605][ T67] worker_thread (kernel/workqueue.c:3304 kernel/workqueue.c:3391)
[ 953.734760][ T67] ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:4347 kernel/locking/lockdep.c:4406)
[ 953.734974][ T67] ? __pfx_worker_thread (kernel/workqueue.c:3337)
[ 953.735157][ T67] ? __pfx_worker_thread (kernel/workqueue.c:3337)
[ 953.735342][ T67] kthread (kernel/kthread.c:389)
[ 953.735544][ T67] ? __pfx_kthread (kernel/kthread.c:342)
[ 953.735722][ T67] ret_from_fork (arch/x86/kernel/process.c:147)
[ 953.735957][ T67] ? __pfx_kthread (kernel/kthread.c:342)


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