======================================
| [ 55.204412][ T11] #3: ffffffff87de7a48 (rtnl_mutex){+.+.}-{4:4}, at: cleanup_net (net/core/net_namespace.c:639)
| [ 55.204805][ T11] #4: ffffffff87dd6630 ((netdev_chain).rwsem){++++}-{4:4}, at: blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
| [   55.205255][   T11]
| [   55.205255][   T11] stack backtrace:
[   55.205930][   T11] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   55.206208][   T11] Workqueue: netns cleanup_net
[   55.206450][   T11] Call Trace:
[   55.206620][   T11]  <TASK>
[ 55.206745][ T11] dump_stack_lvl (lib/dump_stack.c:123)
[ 55.206981][ T11] print_deadlock_bug (kernel/locking/lockdep.c:3040)
[ 55.207211][ T11] validate_chain (kernel/locking/lockdep.c:3894)
[ 55.207437][ T11] ? __pfx_validate_chain (kernel/locking/lockdep.c:3860)
[ 55.207674][ 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)
[ 55.207903][ T11] ? mark_lock (kernel/locking/lockdep.c:4727 (discriminator 3))
[ 55.208081][ T11] __lock_acquire (kernel/locking/lockdep.c:5226)
[ 55.208307][ T11] ? spin_bug (kernel/locking/spinlock_debug.c:57 kernel/locking/spinlock_debug.c:78)
[ 55.208482][ T11] ? debug_object_assert_init (./include/linux/err.h:81 lib/debugobjects.c:1010)
[ 55.208712][ T11] lock_acquire.part.0 (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:5851)
[ 55.208950][ T11] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 55.209245][ T11] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5814)
[ 55.209496][ T11] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 37))
[ 55.209734][ T11] ? lock_acquire (kernel/locking/lockdep.c:5822)
[ 55.209959][ T11] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 55.210236][ 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)
[ 55.210406][ T11] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 55.210698][ T11] ? __pfx_down_read (kernel/locking/rwsem.c:1522)
[ 55.210928][ T11] blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 55.211162][ T11] __dev_close_many (net/core/dev.c:1537 (discriminator 3))
[ 55.211383][ T11] ? __pfx___dev_close_many (net/core/dev.c:1525)
[ 55.211614][ T11] dev_close_many (net/core/dev.c:1588)
[ 55.211841][ T11] ? __lock_release (kernel/locking/lockdep.c:5525)
[ 55.212063][ T11] ? __pfx_dev_close_many (net/core/dev.c:1578)
[ 55.212285][ T11] ? __pfx___lock_release (kernel/locking/lockdep.c:5501)
[ 55.212514][ T11] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5814)
[ 55.212762][ T11] vlan_device_event (net/8021q/vlan.c:451) 8021q
[ 55.213050][ T11] ? net_generic (./include/net/netns/generic.h:51) vxlan
[ 55.213296][ T11] ? __pfx_vlan_device_event (net/8021q/vlan.c:362) 8021q
[ 55.213582][ T11] ? __pfx_vxlan_netdevice_event (drivers/net/vxlan/vxlan_core.c:4737) vxlan
[ 55.213885][ T11] ? packet_notifier (net/packet/af_packet.c:4282)
[ 55.214116][ T11] notifier_call_chain (kernel/notifier.c:85 (discriminator 2))
[ 55.214348][ T11] blocking_notifier_call_chain (kernel/notifier.c:381 kernel/notifier.c:368)
[ 55.214582][ T11] dev_close_many (net/core/dev.c:1591)
[ 55.214814][ T11] ? __lock_release (kernel/locking/lockdep.c:5525)
[ 55.215038][ T11] ? __virt_addr_valid (./include/linux/rcupdate.h:347 ./include/linux/rcupdate.h:962 ./include/linux/mmzone.h:2058 arch/x86/mm/physaddr.c:65)
[ 55.215263][ T11] ? __pfx_dev_close_many (net/core/dev.c:1578)
[ 55.215492][ T11] unregister_netdevice_many_notify (net/core/dev.c:11549)
[ 55.215777][ T11] ? mark_held_locks (kernel/locking/lockdep.c:4321)
[ 55.216015][ T11] ? __pfx_unregister_netdevice_many_notify (net/core/dev.c:11516)
[ 55.216292][ 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)
[ 55.216524][ T11] ? rtnl_is_locked (net/core/rtnetlink.c:163)
[ 55.216751][ T11] ? __pfx_unregister_netdevice_queue (net/core/dev.c:11500)
[ 55.217035][ 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)
[ 55.217257][ T11] ? 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)
[ 55.217537][ T11] cleanup_net (net/core/net_namespace.c:644)
[ 55.217774][ T11] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5814)
[ 55.217998][ T11] ? __pfx_cleanup_net (net/core/net_namespace.c:592)
[ 55.218220][ T11] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 37))
[ 55.218443][ T11] ? lock_acquire (kernel/locking/lockdep.c:5822)
[ 55.218668][ T11] ? process_one_work (kernel/workqueue.c:3205)
[ 55.218897][ T11] process_one_work (kernel/workqueue.c:3229)
[ 55.219128][ T11] ? __pfx___lock_release (kernel/locking/lockdep.c:5501)
[ 55.219359][ T11] ? __pfx_process_one_work (kernel/workqueue.c:3131)
[ 55.219589][ T11] ? assign_work (kernel/workqueue.c:1200)
[ 55.219824][ T11] worker_thread (kernel/workqueue.c:3304 kernel/workqueue.c:3391)
[ 55.220054][ T11] ? __pfx_worker_thread (kernel/workqueue.c:3337)
[ 55.220278][ T11] kthread (kernel/kthread.c:389)
[ 55.220446][ T11] ? __pfx_kthread (kernel/kthread.c:342)
[ 55.220686][ T11] ret_from_fork (arch/x86/kernel/process.c:147)
[ 55.220930][ T11] ? __pfx_kthread (kernel/kthread.c:342)


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