============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
kworker/u4:11/4419 is trying to acquire lock:
ffff88802b4b0218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline]
ffff88802b4b0218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3909 [inline]
ffff88802b4b0218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_queue_xmit+0x1f6e/0x2ed0 net/core/dev.c:4253

but task is already holding lock:
ffff888078aa8258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: spin_trylock include/linux/spinlock.h:373 [inline]
ffff888078aa8258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: qdisc_run_begin include/net/sch_generic.h:173 [inline]
ffff888078aa8258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3871 [inline]
ffff888078aa8258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_queue_xmit+0x10b9/0x2ed0 net/core/dev.c:4253

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock);
  lock(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

6 locks held by kworker/u4:11/4419:
 #0: ffff88802bb69138 ((wq_completion)bat_events){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
 #1: ffffc900034cfd00 ((work_completion)(&(&forw_packet_aggr->delayed_work)->work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
 #2: ffffffff8c11c6c0 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312
 #3: ffff888078aa8258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: spin_trylock include/linux/spinlock.h:373 [inline]
 #3: ffff888078aa8258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: qdisc_run_begin include/net/sch_generic.h:173 [inline]
 #3: ffff888078aa8258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3871 [inline]
 #3: ffff888078aa8258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_queue_xmit+0x10b9/0x2ed0 net/core/dev.c:4253
 #4: ffffffff8c11c6c0 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312
 #5: ffffffff8c11c6c0 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312

stack backtrace:
CPU: 0 PID: 4419 Comm: kworker/u4:11 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Workqueue: bat_events batadv_iv_send_outstanding_bat_ogm_packet
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 __lock_acquire+0x1227/0x7c60 kernel/locking/lockdep.c:-1
 lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
 _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154
 spin_lock include/linux/spinlock.h:363 [inline]
 __dev_xmit_skb net/core/dev.c:3909 [inline]
 __dev_queue_xmit+0x1f6e/0x2ed0 net/core/dev.c:4253
 neigh_hh_output include/net/neighbour.h:493 [inline]
 neigh_output include/net/neighbour.h:507 [inline]
 ip_finish_output2+0xc69/0x1080 net/ipv4/ip_output.c:228
 iptunnel_xmit+0x525/0x960 net/ipv4/ip_tunnel_core.c:82
 ip_tunnel_xmit+0x1b6f/0x2240 net/ipv4/ip_tunnel.c:838
 __gre_xmit net/ipv4/ip_gre.c:474 [inline]
 gre_tap_xmit+0x4f9/0x6e0 net/ipv4/ip_gre.c:751
 __netdev_start_xmit include/linux/netdevice.h:5027 [inline]
 netdev_start_xmit include/linux/netdevice.h:5041 [inline]
 xmit_one net/core/dev.c:3649 [inline]
 dev_hard_start_xmit+0x2a5/0x7e0 net/core/dev.c:3665
 sch_direct_xmit+0x24e/0x4a0 net/sched/sch_generic.c:342
 __dev_xmit_skb net/core/dev.c:3884 [inline]
 __dev_queue_xmit+0x170e/0x2ed0 net/core/dev.c:4253
 batadv_send_skb_packet+0x384/0x5f0 net/batman-adv/send.c:108
 batadv_iv_ogm_send_to_if net/batman-adv/bat_iv_ogm.c:392 [inline]
 batadv_iv_ogm_emit net/batman-adv/bat_iv_ogm.c:420 [inline]
 batadv_iv_send_outstanding_bat_ogm_packet+0x696/0x840 net/batman-adv/bat_iv_ogm.c:1700
 process_one_work+0x863/0x1000 kernel/workqueue.c:2310
 worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>