[v5.15] possible deadlock in flush_workqueue

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d86dfc4d95cd Linux 5.15.106
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17aa5703c80000
kernel config: https://syzkaller.appspot.com/x/.config?x=dca379fe384dda80
dashboard link: https://syzkaller.appspot.com/bug?extid=1c7630d66ab18ae3176d
compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/2c159eb4fcae/disk-d86dfc4d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5f50187f87c7/vmlinux-d86dfc4d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f787f3f09c09/bzImage-d86dfc4d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1c7630...@syzkaller.appspotmail.com

============================================
WARNING: possible recursive locking detected
5.15.106-syzkaller #0 Not tainted
--------------------------------------------
kworker/u5:0/32613 is trying to acquire lock:
ffff888029480138 ((wq_completion)hci0){+.+.}-{0:0}, at: flush_workqueue+0x154/0x1610 kernel/workqueue.c:2826

but task is already holding lock:
ffff888029480138 ((wq_completion)hci0){+.+.}-{0:0}, at: process_one_work+0x78a/0x10c0 kernel/workqueue.c:2279

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

CPU0
----
lock((wq_completion)hci0);
lock((wq_completion)hci0);

*** DEADLOCK ***

May be due to missing lock nesting notation

2 locks held by kworker/u5:0/32613:
#0: ffff888029480138 ((wq_completion)hci0){+.+.}-{0:0}, at: process_one_work+0x78a/0x10c0 kernel/workqueue.c:2279
#1: ffffc9000858fd20 ((work_completion)(&hdev->error_reset)){+.+.}-{0:0}, at: process_one_work+0x7d0/0x10c0 kernel/workqueue.c:2281

stack backtrace:
CPU: 1 PID: 32613 Comm: kworker/u5:0 Not tainted 5.15.106-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023
Workqueue: hci0 hci_error_reset
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
print_deadlock_bug kernel/locking/lockdep.c:2946 [inline]
check_deadlock kernel/locking/lockdep.c:2989 [inline]
validate_chain+0x46cf/0x58b0 kernel/locking/lockdep.c:3774
__lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5011
lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5622
flush_workqueue+0x170/0x1610 kernel/workqueue.c:2826
drain_workqueue+0xc5/0x390 kernel/workqueue.c:2991
destroy_workqueue+0x7b/0xae0 kernel/workqueue.c:4426
hci_release_dev+0x130/0x14c0 net/bluetooth/hci_core.c:4068
bt_host_release+0x7f/0x90 net/bluetooth/hci_sysfs.c:91
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
hci_dev_put include/net/bluetooth/hci_core.h:1203 [inline]
hci_dev_do_close+0xe03/0x1000 net/bluetooth/hci_core.c:1856
hci_error_reset+0xcd/0x160 net/bluetooth/hci_core.c:2340
process_one_work+0x8a1/0x10c0 kernel/workqueue.c:2306
worker_thread+0xaca/0x1280 kernel/workqueue.c:2453
kthread+0x3f6/0x4f0 kernel/kthread.c:319
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298
</TASK>


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.