======================================
| [ 15.888396][ T303] #1: ffffffffa3007e88 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink (net/core/rtnetlink.c:337 net/core/rtnetlink.c:4020)
| [ 15.888809][ T303] #2: ffffffffa2ff6a70 ((netdev_chain).rwsem){++++}-{4:4}, at: blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
| [   15.889282][  T303]
| [   15.889282][  T303] stack backtrace:
[   15.889950][  T303] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[   15.890226][  T303] Call Trace:
[   15.890415][  T303]  <TASK>
[ 15.890537][ T303] dump_stack_lvl (lib/dump_stack.c:123)
[ 15.890787][ T303] print_deadlock_bug (kernel/locking/lockdep.c:3040)
[ 15.891014][ T303] validate_chain (kernel/locking/lockdep.c:3894)
[ 15.891245][ T303] ? __pfx_validate_chain (kernel/locking/lockdep.c:3860)
[ 15.891479][ T303] ? 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)
[ 15.891717][ T303] ? mark_lock (kernel/locking/lockdep.c:4727 (discriminator 3))
[ 15.891894][ T303] __lock_acquire (kernel/locking/lockdep.c:5226)
[ 15.892115][ T303] lock_acquire.part.0 (kernel/locking/lockdep.c:467 kernel/locking/lockdep.c:5851)
[ 15.892344][ T303] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 15.892619][ T303] ? __pfx_lock_acquire.part.0 (kernel/locking/lockdep.c:5814)
[ 15.892837][ T303] ? trace_lock_acquire (./include/trace/events/lock.h:24 (discriminator 37))
[ 15.893063][ T303] ? lock_acquire (kernel/locking/lockdep.c:5822)
[ 15.893308][ T303] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 15.893589][ T303] down_read (./arch/x86/include/asm/preempt.h:79 kernel/locking/rwsem.c:1246 kernel/locking/rwsem.c:1261 kernel/locking/rwsem.c:1526)
[ 15.893771][ T303] ? blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 15.894054][ T303] ? __pfx_down_read (kernel/locking/rwsem.c:1522)
[ 15.894291][ T303] blocking_notifier_call_chain (kernel/notifier.c:380 kernel/notifier.c:368)
[ 15.894508][ T303] netdev_update_features (net/core/dev.c:10314)
[ 15.894745][ T303] ? __pfx_netdev_update_features (net/core/dev.c:10311)
[ 15.895057][ T303] vlan_device_event (net/8021q/vlan.c:430 (discriminator 2))
[ 15.895318][ T303] ? __pfx_vlan_device_event (net/8021q/vlan.c:362)
[ 15.895565][ T303] ? __pfx_br_device_event (net/bridge/br.c:29)
[ 15.895814][ T303] ? packet_notifier (net/packet/af_packet.c:4282)
[ 15.896055][ T303] notifier_call_chain (kernel/notifier.c:85 (discriminator 2))
[ 15.896304][ T303] blocking_notifier_call_chain (kernel/notifier.c:381 kernel/notifier.c:368)
[ 15.896549][ T303] netdev_update_features (net/core/dev.c:10314)
[ 15.896808][ T303] ? __pfx_netdev_update_features (net/core/dev.c:10311)
[ 15.897112][ T303] br_add_if (net/bridge/br_if.c:657)
[ 15.897298][ T303] ? rtnl_is_locked (net/core/rtnetlink.c:163)
[ 15.897541][ T303] ? netdev_master_upper_dev_get (net/core/dev.c:7230)
[ 15.897841][ T303] rtnl_newlink_create (net/core/rtnetlink.c:3813)
[ 15.898084][ T303] ? __pfx_rtnl_newlink_create (net/core/rtnetlink.c:3762)
[ 15.898330][ T303] ? rtnl_newlink (net/core/rtnetlink.c:337 net/core/rtnetlink.c:4020)
[ 15.898587][ T303] ? __pfx___mutex_lock (kernel/locking/mutex.c:734)
[ 15.898822][ T303] ? __pfx___lock_release (kernel/locking/lockdep.c:5501)
[ 15.899060][ T303] __rtnl_newlink (net/core/rtnetlink.c:3906)
[ 15.899310][ T303] rtnl_newlink (net/core/rtnetlink.c:345 net/core/rtnetlink.c:4022)
[ 15.899548][ T303] ? __pfx_rtnl_newlink (net/core/rtnetlink.c:3912)
[ 15.899791][ T303] ? find_held_lock (kernel/locking/lockdep.c:5339)
[ 15.900021][ T303] ? __pfx___lock_release (kernel/locking/lockdep.c:5501)
[ 15.900254][ T303] ? rtnetlink_rcv_msg (./include/linux/rcupdate.h:347 ./include/linux/rcupdate.h:880 net/core/rtnetlink.c:6909)
[ 15.900478][ T303] ? __pfx_rtnl_newlink (net/core/rtnetlink.c:3912)
[ 15.900712][ T303] rtnetlink_rcv_msg (net/core/rtnetlink.c:6911)
[ 15.900945][ T303] ? __pfx_rtnetlink_rcv_msg (net/core/rtnetlink.c:6814)
[ 15.901172][ T303] ? 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)
[ 15.901416][ T303] ? mark_lock (kernel/locking/lockdep.c:4727 (discriminator 3))
[ 15.901593][ T303] ? __lock_acquire (kernel/locking/lockdep.c:5226)
[ 15.901818][ T303] netlink_rcv_skb (net/netlink/af_netlink.c:2543)
[ 15.902055][ T303] ? __pfx_rtnetlink_rcv_msg (net/core/rtnetlink.c:6814)
[ 15.902281][ T303] ? __pfx_netlink_rcv_skb (net/netlink/af_netlink.c:2520)
[ 15.902520][ T303] ? netlink_deliver_tap (./include/linux/rcupdate.h:347 ./include/linux/rcupdate.h:880 net/netlink/af_netlink.c:340)
[ 15.902748][ T303] ? netlink_deliver_tap (./include/linux/rcupdate.h:347 ./include/linux/rcupdate.h:880 ./include/net/netns/generic.h:48 net/netlink/af_netlink.c:333)
[ 15.902977][ T303] netlink_unicast (net/netlink/af_netlink.c:1322 net/netlink/af_netlink.c:1348)
[ 15.903205][ T303] ? __pfx_netlink_unicast (net/netlink/af_netlink.c:1333)
[ 15.903440][ T303] ? find_held_lock (kernel/locking/lockdep.c:5339)
[ 15.903687][ T303] netlink_sendmsg (net/netlink/af_netlink.c:1892)
[ 15.903916][ T303] ? __pfx_netlink_sendmsg (net/netlink/af_netlink.c:1811)
[ 15.904148][ T303] ____sys_sendmsg (net/socket.c:711 net/socket.c:726 net/socket.c:2594)
[ 15.904382][ T303] ? __pfx_____sys_sendmsg (net/socket.c:2540)
[ 15.904602][ T303] ? __pfx_copy_msghdr_from_user (net/socket.c:2520)
[ 15.904885][ T303] ___sys_sendmsg (net/socket.c:2650)
[ 15.905119][ T303] ? __pfx____sys_sendmsg (net/socket.c:2637)
[ 15.905358][ T303] ? __pfx___lock_release (kernel/locking/lockdep.c:5501)
[ 15.905587][ T303] ? __pfx_handle_pte_fault (mm/memory.c:5758)
[ 15.905812][ T303] ? __handle_mm_fault (mm/memory.c:5944)
[ 15.906029][ T303] ? __pfx___handle_mm_fault (mm/memory.c:5853)
[ 15.906245][ T303] ? mt_find (lib/maple_tree.c:6949)
[ 15.906413][ T303] ? find_held_lock (kernel/locking/lockdep.c:5339)
[ 15.906631][ T303] ? __lock_release (kernel/locking/lockdep.c:5525)
[ 15.906869][ T303] ? do_user_addr_fault (./include/linux/mmap_lock.h:172 arch/x86/mm/fault.c:1417)
[ 15.907110][ T303] __sys_sendmsg (net/socket.c:2680)
[ 15.907354][ T303] ? __pfx___sys_sendmsg (net/socket.c:2665)
[ 15.907607][ T303] ? do_user_addr_fault (./include/linux/mmap_lock.h:172 arch/x86/mm/fault.c:1417)
[ 15.907852][ T303] do_syscall_64 (arch/x86/entry/common.c:52 arch/x86/entry/common.c:83)
[ 15.908098][ T303] entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
[   15.908398][  T303] RIP: 0033:0x7f48018169a7
[ 15.908672][ T303] Code: Unable to access opcode bytes at 0x7f480181697d.

Code starting with the faulting instruction
===========================================
[   15.908967][  T303] RSP: 002b:00007ffeb88a4858 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
[   15.909307][  T303] RAX: ffffffffffffffda RBX: 00007ffeb88a4f90 RCX: 00007f48018169a7
[   15.909675][  T303] RDX: 0000000000000000 RSI: 00007ffeb88a48c0 RDI: 0000000000000005
[   15.910028][  T303] RBP: 0000000000000006 R08: 000000000000006c R09: 0000000000000000
[   15.910386][  T303] R10: 00007f4801865ac0 R11: 0000000000000246 R12: 00007ffeb88a4fc8


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