unregister_netdevice: waiting for batadv_slave_0 to become free. Usage count = 2
ref_tracker: batadv_slave_0@ffff88805efca610 has 1/1 users at
     __netdev_tracker_alloc include/linux/netdevice.h:4331 [inline]
     netdev_hold include/linux/netdevice.h:4360 [inline]
     batadv_hardif_add_interface net/batman-adv/hard-interface.c:888 [inline]
     batadv_hard_if_event+0x122c/0x1a50 net/batman-adv/hard-interface.c:968
     notifier_call_chain+0x1b3/0x3e0 kernel/notifier.c:85
     call_netdevice_notifiers_extack net/core/dev.c:2214 [inline]
     call_netdevice_notifiers net/core/dev.c:2228 [inline]
     register_netdevice+0x1608/0x1af0 net/core/dev.c:11037
     veth_newlink+0x5cc/0xa50 drivers/net/veth.c:1847
     rtnl_newlink_create+0x305/0xaf0 net/core/rtnetlink.c:3833
     __rtnl_newlink net/core/rtnetlink.c:3950 [inline]
     rtnl_newlink+0x16d6/0x1c70 net/core/rtnetlink.c:4065
     rtnetlink_rcv_msg+0x7cf/0xb70 net/core/rtnetlink.c:6955
     netlink_rcv_skb+0x219/0x490 net/netlink/af_netlink.c:2534
     netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline]
     netlink_unicast+0x75b/0x8d0 net/netlink/af_netlink.c:1339
     netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1883
     sock_sendmsg_nosec net/socket.c:712 [inline]
     __sock_sendmsg+0x219/0x270 net/socket.c:727
     __sys_sendto+0x3bd/0x520 net/socket.c:2180
     __do_sys_sendto net/socket.c:2187 [inline]
     __se_sys_sendto net/socket.c:2183 [inline]
     __x64_sys_sendto+0xde/0x100 net/socket.c:2183
     do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
     do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
     entry_SYSCALL_64_after_hwframe+0x77/0x7f