Bluetooth: hci6: Controller not accepting commands anymore: ncmd = 0
Bluetooth: hci6: Injecting HCI hardware error event
Bluetooth: hci6: hardware error 0x00
============================================
WARNING: possible recursive locking detected
6.10.0-next-20240719-syzkaller #0 Not tainted
--------------------------------------------
kworker/u9:1/13518 is trying to acquire lock:
ffff888011a44148 ((wq_completion)hci6){+.+.}-{0:0}, at: touch_wq_lockdep_map kernel/workqueue.c:3876 [inline]
ffff888011a44148 ((wq_completion)hci6){+.+.}-{0:0}, at: __flush_workqueue+0x1b0/0x1710 kernel/workqueue.c:3918

but task is already holding lock:
ffff888011a44148 ((wq_completion)hci6){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3206 [inline]
ffff888011a44148 ((wq_completion)hci6){+.+.}-{0:0}, at: process_scheduled_works+0x90a/0x1830 kernel/workqueue.c:3312

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

       CPU0
       ----
  lock((wq_completion)hci6);
  lock((wq_completion)hci6);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

2 locks held by kworker/u9:1/13518:
 #0: ffff888011a44148 ((wq_completion)hci6){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3206 [inline]
 #0: ffff888011a44148 ((wq_completion)hci6){+.+.}-{0:0}, at: process_scheduled_works+0x90a/0x1830 kernel/workqueue.c:3312
 #1: ffffc900020bfd00 ((work_completion)(&hdev->error_reset)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3207 [inline]
 #1: ffffc900020bfd00 ((work_completion)(&hdev->error_reset)){+.+.}-{0:0}, at: process_scheduled_works+0x945/0x1830 kernel/workqueue.c:3312

stack backtrace:
CPU: 0 UID: 0 PID: 13518 Comm: kworker/u9:1 Not tainted 6.10.0-next-20240719-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
Workqueue: hci6 hci_error_reset
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_deadlock_bug+0x483/0x620 kernel/locking/lockdep.c:3034
 check_deadlock kernel/locking/lockdep.c:3086 [inline]
 validate_chain+0x15e2/0x5920 kernel/locking/lockdep.c:3888
 __lock_acquire+0x1384/0x2050 kernel/locking/lockdep.c:5199
 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5822
 touch_wq_lockdep_map kernel/workqueue.c:3876 [inline]
 __flush_workqueue+0x1c9/0x1710 kernel/workqueue.c:3918
 drain_workqueue+0xc9/0x3a0 kernel/workqueue.c:4082
 destroy_workqueue+0xba/0xc40 kernel/workqueue.c:5781
 hci_release_dev+0x169/0x16b0 net/bluetooth/hci_core.c:2734
 bt_host_release+0x83/0x90 net/bluetooth/hci_sysfs.c:94
 device_release+0x99/0x1c0
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x22f/0x480 lib/kobject.c:737
 process_one_work kernel/workqueue.c:3231 [inline]
 process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312
 worker_thread+0x86d/0xd40 kernel/workqueue.c:3390
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:144
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>