======================================
| [ 15.120671][ T11] #3: ffffffffa4807e88 (rtnl_mutex){+.+.}-{4:4}, at: cleanup_net (net/core/net_namespace.c:639)
| [ 15.120910][ T11] #4: ffffffffa47f6a70 ((netdev_chain).rwsem){++++}-{4:4}, at: blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
| [   15.121187][   T11]
| [   15.121187][   T11] stack backtrace:
[   15.121601][   T11] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   15.121769][   T11] Workqueue: netns cleanup_net
[   15.121914][   T11] Call Trace:
[   15.122016][   T11]  <TASK>
[ 15.122086][ T11] dump_stack_lvl (lib/dump_stack.c:123)
[ 15.122247][ T11] print_deadlock_bug (kernel/locking/lockdep.c:3040)
[ 15.122382][ T11] validate_chain (kernel/locking/lockdep.c:3894)
[ 15.122519][ T11] ? __pfx_validate_chain (kernel/locking/lockdep.c:3860)
[ 15.122655][ 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)
[ 15.122787][ T11] ? mark_lock (kernel/locking/lockdep.c:4727 (discriminator 3))
[ 15.122890][ T11] __lock_acquire (kernel/locking/lockdep.c:5226)
[ 15.123027][ T11] ? spin_bug (./include/linux/pid.h:232 kernel/locking/spinlock_debug.c:64 kernel/locking/spinlock_debug.c:78)
[ 15.123129][ T11] ? debug_object_assert_init (./include/linux/err.h:81 lib/debugobjects.c:1010)
[ 15.123269][ T11] lock_acquire.part.0 (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:5851)
[ 15.123401][ T11] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 15.123568][ T11] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5814)
[ 15.123700][ T11] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 37))
[ 15.123833][ T11] ? lock_acquire (kernel/locking/lockdep.c:5822)
[ 15.123966][ T11] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 15.124134][ 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)
[ 15.124240][ T11] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 15.124403][ T11] ? __pfx_down_read (kernel/locking/rwsem.c:1522)
[ 15.124538][ T11] blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 15.124673][ T11] __dev_close_many (net/core/dev.c:1537 (discriminator 3))
[ 15.124807][ T11] ? __pfx___dev_close_many (net/core/dev.c:1525)
[ 15.124942][ T11] dev_close_many (net/core/dev.c:1588)
[ 15.125075][ T11] ? __pfx_dev_close_many (net/core/dev.c:1578)
[ 15.125214][ T11] ? ipv6_mc_down (net/ipv6/mcast.c:1140 net/ipv6/mcast.c:2777)
[ 15.125352][ T11] vlan_device_event (net/8021q/vlan.c:451)
[ 15.125488][ T11] ? __pfx_vlan_device_event (net/8021q/vlan.c:362)
[ 15.125622][ T11] ? __pfx_br_device_event (net/bridge/br.c:29)
[ 15.125759][ T11] ? packet_notifier (net/packet/af_packet.c:4282)
[ 15.125896][ T11] notifier_call_chain (kernel/notifier.c:85 (discriminator 2))
[ 15.126031][ T11] blocking_notifier_call_chain (kernel/notifier.c:381 kernel/notifier.c:368)
[ 15.126167][ T11] dev_close_many (net/core/dev.c:1591)
[ 15.126303][ T11] ? __pfx_dev_close_many (net/core/dev.c:1578)
[ 15.126446][ T11] unregister_netdevice_many_notify (net/core/dev.c:11549)
[ 15.126611][ T11] ? __lock_release (kernel/locking/lockdep.c:5525)
[ 15.126746][ T11] ? net_generic (./include/linux/rcupdate.h:347 ./include/linux/rcupdate.h:880 ./include/net/netns/generic.h:48)
[ 15.126883][ T11] ? __pfx_unregister_netdevice_many_notify (net/core/dev.c:11516)
[ 15.127047][ T11] ? rtnl_is_locked (net/core/rtnetlink.c:163)
[ 15.127182][ T11] ? unregister_netdevice_queue (net/core/dev.c:11501)
[ 15.127348][ T11] ? __pfx_unregister_netdevice_queue (net/core/dev.c:11500)
[ 15.127512][ T11] ? net_generic (./include/linux/rcupdate.h:347 ./include/linux/rcupdate.h:880 ./include/net/netns/generic.h:48)
[ 15.127646][ 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)
[ 15.127779][ 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)
[ 15.127946][ T11] cleanup_net (net/core/net_namespace.c:644)
[ 15.128078][ T11] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5814)
[ 15.128216][ T11] ? __pfx_cleanup_net (net/core/net_namespace.c:592)
[ 15.128348][ T11] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 37))
[ 15.128482][ T11] ? lock_acquire (kernel/locking/lockdep.c:5822)
[ 15.128614][ T11] ? process_one_work (kernel/workqueue.c:3205)
[ 15.128748][ T11] process_one_work (kernel/workqueue.c:3229)
[ 15.128883][ T11] ? __pfx___lock_release (kernel/locking/lockdep.c:5501)
[ 15.129018][ T11] ? __pfx_process_one_work (kernel/workqueue.c:3131)
[ 15.129157][ T11] ? assign_work (kernel/workqueue.c:1200)
[ 15.129293][ T11] worker_thread (kernel/workqueue.c:3304 kernel/workqueue.c:3391)
[ 15.129428][ T11] ? __pfx_worker_thread (kernel/workqueue.c:3337)
[ 15.129563][ T11] kthread (kernel/kthread.c:389)
[ 15.129664][ T11] ? __pfx_kthread (kernel/kthread.c:342)
[ 15.129797][ T11] ret_from_fork (arch/x86/kernel/process.c:147)
[ 15.129932][ T11] ? __pfx_kthread (kernel/kthread.c:342)


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