unregister_netdevice: waiting for batadv_slave_0 to become free. Usage count = 2
ref_tracker: netdev@ffff888021f9e610 has 1/1 users at
     __netdev_tracker_alloc include/linux/netdevice.h:4349 [inline]
     netdev_hold include/linux/netdevice.h:4378 [inline]
     netdev_hold include/linux/netdevice.h:4373 [inline]
     batadv_hardif_add_interface net/batman-adv/hard-interface.c:877 [inline]
     batadv_hard_if_event+0xbb7/0x1550 net/batman-adv/hard-interface.c:957
     notifier_call_chain+0xb9/0x410 kernel/notifier.c:85
     call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:2229
     call_netdevice_notifiers_extack net/core/dev.c:2267 [inline]
     call_netdevice_notifiers net/core/dev.c:2281 [inline]
     register_netdevice+0x182e/0x2270 net/core/dev.c:11244
     veth_newlink+0x446/0xa00 drivers/net/veth.c:1884
     rtnl_newlink_create net/core/rtnetlink.c:3825 [inline]
     __rtnl_newlink net/core/rtnetlink.c:3942 [inline]
     rtnl_newlink+0xc42/0x2000 net/core/rtnetlink.c:4057
     rtnetlink_rcv_msg+0x95e/0xe90 net/core/rtnetlink.c:6946
     netlink_rcv_skb+0x158/0x420 net/netlink/af_netlink.c:2552
     netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
     netlink_unicast+0x5a7/0x870 net/netlink/af_netlink.c:1346
     netlink_sendmsg+0x8d1/0xdd0 net/netlink/af_netlink.c:1896
     sock_sendmsg_nosec net/socket.c:714 [inline]
     __sock_sendmsg net/socket.c:729 [inline]
     __sys_sendto+0x4a0/0x520 net/socket.c:2228
     __do_sys_sendto net/socket.c:2235 [inline]
     __se_sys_sendto net/socket.c:2231 [inline]
     __x64_sys_sendto+0xe0/0x1c0 net/socket.c:2231
     do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
     do_syscall_64+0xcd/0x490 arch/x86/entry/syscall_64.c:94
     entry_SYSCALL_64_after_hwframe+0x77/0x7f