syzbot

Bluetooth: hci4: hardware error 0x00
============================================
WARNING: possible recursive locking detected
5.15.163-syzkaller #0 Not tainted
--------------------------------------------
kworker/u5:2/3578 is trying to acquire lock:
ffff88801cd09938 ((wq_completion)hci4){+.+.}-{0:0}, at: flush_workqueue+0x154/0x1610 kernel/workqueue.c:2830

but task is already holding lock:
ffff88801cd09938 ((wq_completion)hci4){+.+.}-{0:0}, at: process_one_work+0x78a/0x10c0 kernel/workqueue.c:2283

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

       CPU0
       ----
  lock((wq_completion)hci4);
  lock((wq_completion)hci4);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

2 locks held by kworker/u5:2/3578:
 #0: ffff88801cd09938 ((wq_completion)hci4){+.+.}-{0:0}, at: process_one_work+0x78a/0x10c0 kernel/workqueue.c:2283
 #1: ffffc90002e97d20 ((work_completion)(&hdev->error_reset)){+.+.}-{0:0}, at: process_one_work+0x7d0/0x10c0 kernel/workqueue.c:2285

stack backtrace:
CPU: 0 PID: 3578 Comm: kworker/u5:2 Not tainted 5.15.163-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
Workqueue: hci4 hci_error_reset
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2d0 lib/dump_stack.c:106
 print_deadlock_bug kernel/locking/lockdep.c:2946 [inline]
 check_deadlock kernel/locking/lockdep.c:2989 [inline]
 validate_chain+0x46d2/0x5930 kernel/locking/lockdep.c:3775
 __lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5012
 lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
 flush_workqueue+0x170/0x1610 kernel/workqueue.c:2830
 drain_workqueue+0xc5/0x390 kernel/workqueue.c:2995
 destroy_workqueue+0x7b/0xae0 kernel/workqueue.c:4439
 hci_release_dev+0x165/0x1620 net/bluetooth/hci_core.c:4071
 bt_host_release+0x7f/0x90 net/bluetooth/hci_sysfs.c:92
 device_release+0x91/0x1c0
 kobject_cleanup lib/kobject.c:713 [inline]
 kobject_release lib/kobject.c:744 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x224/0x460 lib/kobject.c:761
 process_one_work+0x8a1/0x10c0 kernel/workqueue.c:2310
 worker_thread+0xaca/0x1280 kernel/workqueue.c:2457
 kthread+0x3f6/0x4f0 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>