======================================
| [ 821.365492][ T11] #3: ffffffff9d207e88 (rtnl_mutex){+.+.}-{4:4}, at: default_device_exit_batch (net/core/dev.c:12109)
| [ 821.365791][ T11] #4: ffffffff9d1f6a70 ((netdev_chain).rwsem){++++}-{4:4}, at: blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
| [  821.366095][   T11]
| [  821.366095][   T11] stack backtrace:
[  821.366540][   T11] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[  821.366731][   T11] Workqueue: netns cleanup_net
[  821.366886][   T11] Call Trace:
[  821.367000][   T11]  <TASK>
[ 821.367077][ T11] dump_stack_lvl (lib/dump_stack.c:123)
[ 821.367236][ T11] print_deadlock_bug (kernel/locking/lockdep.c:3040)
[ 821.367415][ T11] validate_chain (kernel/locking/lockdep.c:3894)
[ 821.367567][ T11] ? __pfx_validate_chain (kernel/locking/lockdep.c:3860)
[ 821.367715][ 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)
[ 821.367863][ T11] ? mark_lock (kernel/locking/lockdep.c:4727 (discriminator 3))
[ 821.367981][ T11] __lock_acquire (kernel/locking/lockdep.c:5226)
[ 821.368133][ T11] lock_acquire.part.0 (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:5851)
[ 821.368283][ T11] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 821.368468][ T11] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5814)
[ 821.368618][ T11] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 37))
[ 821.368767][ T11] ? lock_acquire (kernel/locking/lockdep.c:5822)
[ 821.368918][ T11] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 821.369102][ 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)
[ 821.369219][ T11] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 821.369404][ T11] ? __pfx_down_read (kernel/locking/rwsem.c:1522)
[ 821.369549][ T11] ? __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)
[ 821.369703][ T11] blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 821.369858][ 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))
[ 821.370014][ T11] ? __pfx___netdev_upper_dev_unlink (net/core/dev.c:8151)
[ 821.370207][ T11] ? synchronize_rcu_expedited (kernel/rcu/tree_exp.h:995 (discriminator 1))
[ 821.370396][ T11] ? __pfx_autoremove_wake_function (kernel/sched/wait.c:383)
[ 821.370584][ T11] ? __pfx___mutex_unlock_slowpath (kernel/locking/mutex.c:890)
[ 821.370775][ T11] netdev_upper_dev_unlink (net/core/dev.c:8190)
[ 821.370924][ T11] ? __pfx_netdev_upper_dev_unlink (net/core/dev.c:8190)
[ 821.371110][ 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)
[ 821.371257][ T11] ? rtnl_is_locked (net/core/rtnetlink.c:163)
[ 821.371404][ T11] ? netdev_master_upper_dev_get (net/core/dev.c:7230)
[ 821.371591][ T11] ovs_netdev_detach_dev (net/openvswitch/vport-netdev.c:158 (discriminator 11)) openvswitch
[ 821.371792][ T11] ? ovs_netdev_get_vport (net/openvswitch/vport-netdev.c:196 (discriminator 3)) openvswitch
[ 821.371987][ T11] dp_device_event (net/openvswitch/dp_notify.c:77) openvswitch
[ 821.372186][ T11] ? trace_notifier_run (./include/trace/events/notifier.h:59 (discriminator 37))
[ 821.372338][ T11] notifier_call_chain (kernel/notifier.c:85 (discriminator 2))
[ 821.372489][ T11] blocking_notifier_call_chain (kernel/notifier.c:381 kernel/notifier.c:368)
[ 821.372638][ T11] unregister_netdevice_many_notify (net/core/dev.c:11575)
[ 821.372824][ T11] ? __pfx_unregister_netdevice_many_notify (net/core/dev.c:11516)
[ 821.373007][ T11] ? default_device_exit_batch (net/core/dev.c:12109)
[ 821.373160][ T11] ? rtnl_is_locked (net/core/rtnetlink.c:163)
[ 821.373308][ T11] ? unregister_netdevice_queue (net/core/dev.c:11501)
[ 821.373497][ T11] ? __pfx_unregister_netdevice_queue (net/core/dev.c:11500)
[ 821.373678][ T11] ? __pfx_unregister_netdevice_queue (net/core/dev.c:11500)
[ 821.373862][ T11] default_device_exit_batch (net/core/dev.c:12123)
[ 821.374012][ T11] ? __pfx_default_device_exit_batch (net/core/dev.c:12098)
[ 821.374192][ T11] ? ops_exit_list (net/core/net_namespace.c:171 (discriminator 3))
[ 821.374344][ T11] cleanup_net (net/core/net_namespace.c:647 (discriminator 3))
[ 821.374491][ T11] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5814)
[ 821.374644][ T11] ? __pfx_cleanup_net (net/core/net_namespace.c:592)
[ 821.374791][ T11] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 37))
[ 821.374938][ T11] ? lock_acquire (kernel/locking/lockdep.c:5822)
[ 821.375082][ T11] ? process_one_work (kernel/workqueue.c:3205)
[ 821.375232][ T11] process_one_work (kernel/workqueue.c:3229)
[ 821.375380][ T11] ? __pfx___lock_release (kernel/locking/lockdep.c:5501)
[ 821.375529][ T11] ? __pfx_process_one_work (kernel/workqueue.c:3131)
[ 821.375683][ T11] ? assign_work (kernel/workqueue.c:1200)
[ 821.375837][ T11] worker_thread (kernel/workqueue.c:3304 kernel/workqueue.c:3391)
[ 821.375986][ T11] ? __pfx_worker_thread (kernel/workqueue.c:3337)
[ 821.376133][ T11] kthread (kernel/kthread.c:389)
[ 821.376245][ T11] ? __pfx_kthread (kernel/kthread.c:342)
[ 821.376395][ T11] ret_from_fork (arch/x86/kernel/process.c:147)
[ 821.376548][ T11] ? __pfx_kthread (kernel/kthread.c:342)


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