[v6.1] INFO: task hung in hci_unregister_dev

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: fb28aa725e05 Linux 6.1.180
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=113f4bb9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=31dfefc4a14efea3
dashboard link: https://syzkaller.appspot.com/bug?extid=907babc84ded273b9e35
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9a6fe2a54d0f/disk-fb28aa72.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/742b23a1d931/vmlinux-fb28aa72.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b3f257c16d2e/bzImage-fb28aa72.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+907bab...@syzkaller.appspotmail.com

INFO: task syz.3.76:4760 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.76 state:D stack:26288 pid:4760 ppid:4287 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5246 [inline]
__schedule+0x107f/0x4030 kernel/sched/core.c:6563
schedule+0xb9/0x180 kernel/sched/core.c:6639
schedule_timeout+0xbd/0x2d0 kernel/time/timer.c:2144
do_wait_for_common kernel/sched/completion.c:85 [inline]
__wait_for_common kernel/sched/completion.c:106 [inline]
wait_for_common kernel/sched/completion.c:117 [inline]
wait_for_completion+0x2c2/0x590 kernel/sched/completion.c:138
__flush_work+0x938/0xac0 kernel/workqueue.c:3076
__cancel_work_timer+0x3f4/0x560 kernel/workqueue.c:3163
hci_unregister_dev+0x17c/0x500 net/bluetooth/hci_core.c:2726
hci_uart_tty_close+0x268/0x330 drivers/bluetooth/hci_ldisc.c:578
tty_ldisc_kill+0xa6/0x1a0 drivers/tty/tty_ldisc.c:614
tty_ldisc_release+0x170/0x200 drivers/tty/tty_ldisc.c:782
tty_release_struct+0x26/0xd0 drivers/tty/tty_io.c:1689
tty_release+0xbc5/0x14f0 drivers/tty/tty_io.c:1860
__fput+0x20a/0x8b0 fs/file_table.c:320
task_work_run+0x1d0/0x260 kernel/task_work.c:203
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fb277b9e019
RSP: 002b:00007ffeb8196018 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007fb277e27da0 RCX: 00007fb277b9e019
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007fb277e27da0 R08: 0000000000000006 R09: 0000000000000000
R10: 00007fb277e27cb0 R11: 0000000000000246 R12: 0000000000019ebf
R13: 00007fb277e25fac R14: 0000000000019bc7 R15: 00007ffeb8196120
</TASK>

Showing all locks held in the system:
3 locks held by kworker/0:0/7:
#0: ffff88814cc17138 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
#1: ffffc900000c7d00 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
#2: ffffffff8dd5b968 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_dad_work+0xc4/0x1500 net/ipv6/addrconf.c:4138
1 lock held by rcu_tasks_kthre/12:
#0: ffffffff8cb2e4f0 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xef0 kernel/rcu/tasks.h:517
1 lock held by rcu_tasks_trace/13:
#0: ffffffff8cb2ed10 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xef0 kernel/rcu/tasks.h:517
2 locks held by kworker/1:0/22:
#0: ffff888017472138 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
#1: ffffc900001c7d00 ((work_completion)(&rew->rew_work)){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
1 lock held by khungtaskd/27:
#0: ffffffff8cb2db60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
#0: ffffffff8cb2db60 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
#0: ffffffff8cb2db60 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x51/0x290 kernel/locking/lockdep.c:6527
2 locks held by dhcpcd/3932:
#0: ffffffff8ddbc170 (cb_lock){++++}-{3:3}, at: genl_rcv+0x15/0x40 net/netlink/genetlink.c:860
#1: ffffffff8dd5b968 (rtnl_mutex){+.+.}-{3:3}, at: nl80211_pre_doit+0x5a/0x890 net/wireless/nl80211.c:16372
2 locks held by getty/4026:
#0: ffff88807e348098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:244
#1: ffffc9000327b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x41e/0x1360 drivers/tty/n_tty.c:2198
3 locks held by kworker/u5:4/4285:
#0: ffff888055115938 ((wq_completion)hci5){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
#1: ffffc90003ea7d00 ((work_completion)(&hdev->power_on)){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
#2: ffff88805669d4b8 (&hdev->req_lock){+.+.}-{3:3}, at: hci_dev_do_open net/bluetooth/hci_core.c:455 [inline]
#2: ffff88805669d4b8 (&hdev->req_lock){+.+.}-{3:3}, at: hci_power_on+0x19f/0x700 net/bluetooth/hci_core.c:963
3 locks held by kworker/1:4/4318:
#0: ffff88814cc17138 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
#1: ffffc90004017d00 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
#2: ffffffff8dd5b968 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_dad_work+0xc4/0x1500 net/ipv6/addrconf.c:4138
5 locks held by kworker/u4:30/4574:
#0: ffff88801761e938 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
#1: ffffc900052e7d00 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
#2: ffffffff8dd4ead0 (pernet_ops_rwsem){++++}-{3:3}, at: cleanup_net+0x148/0xba0 net/core/net_namespace.c:594
#3: ffffffff8dd5b968 (rtnl_mutex){+.+.}-{3:3}, at: xfrmi_exit_batch_net+0xb8/0x360 net/xfrm/xfrm_interface_core.c:954
#4: ffffffff8cb33838 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:291 [inline]
#4: ffffffff8cb33838 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x2ec/0x890 kernel/rcu/tree_exp.h:962
2 locks held by kworker/u4:35/4579:
3 locks held by kworker/u4:103/4647:
#0: ffff888017479138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
#1: ffffc90005b87d00 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work+0x7b4/0x1160 kernel/workqueue.c:2267
#2: ffffffff8dd5b968 (rtnl_mutex){+.+.}-{3:3}, at: linkwatch_event+0xa/0x50 net/core/link_watch.c:263
1 lock held by syz.3.76/4760:
#0: ffff888023cdf098 (&tty->ldisc_sem){++++}-{0:0}, at: __tty_ldisc_lock drivers/tty/tty_ldisc.c:290 [inline]
#0: ffff888023cdf098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_lock_pair_timeout drivers/tty/tty_ldisc.c:353 [inline]
#0: ffff888023cdf098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_lock_pair drivers/tty/tty_ldisc.c:367 [inline]
#0: ffff888023cdf098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_release+0x10c/0x200 drivers/tty/tty_ldisc.c:781
1 lock held by iou-wrk-5196/5197:
#0: ffffffff96d4d888 (&ls_lock){+.+.}-{3:3}, at: __dlm_new_lockspace+0xad/0x22b0 fs/dlm/lockspace.c:713
1 lock held by dlm_recoverd/5202:
#0: ffff88803e7e8ca0 (&ls->ls_in_recovery){+.+.}-{3:3}, at: dlm_recoverd+0xa6/0x1df0 fs/dlm/recoverd.c:312
1 lock held by syz-executor/5922:
#0: ffffffff8dd5b968 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:74 [inline]
#0: ffffffff8dd5b968 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x80d/0xfb0 net/core/rtnetlink.c:6163
1 lock held by syz-executor/5925:
#0: ffffffff8dd5b968 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:74 [inline]
#0: ffffffff8dd5b968 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x80d/0xfb0 net/core/rtnetlink.c:6163
1 lock held by syz-executor/5928:
#0: ffffffff8dd5b968 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:74 [inline]
#0: ffffffff8dd5b968 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x80d/0xfb0 net/core/rtnetlink.c:6163
1 lock held by syz-executor/5931:
#0: ffffffff8dd5b968 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:74 [inline]
#0: ffffffff8dd5b968 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x80d/0xfb0 net/core/rtnetlink.c:6163

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 27 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<TASK>
dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
nmi_cpu_backtrace+0x3e6/0x460 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x1d4/0x450 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:220 [inline]
watchdog+0xf0e/0xf50 kernel/hung_task.c:377
kthread+0x29d/0x330 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 3627 Comm: klogd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:lookup_chain_cache kernel/locking/lockdep.c:3723 [inline]
RIP: 0010:lookup_chain_cache_add kernel/locking/lockdep.c:3743 [inline]
RIP: 0010:validate_chain kernel/locking/lockdep.c:3798 [inline]
RIP: 0010:__lock_acquire+0x14c9/0x7c40 kernel/locking/lockdep.c:5063
Code: b8 eb 83 b5 80 46 86 c8 61 49 0f af c6 48 c1 e8 2d 4c 8d 3c c5 80 01 68 90 4c 89 f8 48 c1 e8 03 48 89 44 24 30 42 80 3c 00 00 <74> 12 4c 89 ff e8 9d 47 6f 00 49 b8 00 00 00 00 00 fc ff df 49 8b
RSP: 0018:ffffc900032a72e0 EFLAGS: 00000046
RAX: 1ffffffff213518a RBX: 0000000000000034 RCX: ffffffff816412d5
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff90b10240
RBP: ffffc900032a7510 R08: dffffc0000000000 R09: 1ffffffff2162048
R10: dffffc0000000000 R11: fffffbfff2162049 R12: ffff88807c4b8ad8
R13: ffff88807c4b8000 R14: 45bf6bd8f37815c5 R15: ffffffff909a8c50
FS: 00007f554069dc80(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007facb374b432 CR3: 000000007e209000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5676
_raw_spin_lock_nested+0x2e/0x40 kernel/locking/spinlock.c:378
raw_spin_rq_lock_nested+0x25/0x130 kernel/sched/core.c:538
raw_spin_rq_lock kernel/sched/sched.h:1362 [inline]
rq_lock kernel/sched/sched.h:1652 [inline]
__schedule+0x2d4/0x4030 kernel/sched/core.c:6479
preempt_schedule_irq+0xbb/0x160 kernel/sched/core.c:6875
irqentry_exit+0x63/0x70 kernel/entry/common.c:439
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:get_data+0x1/0x840 kernel/printk/printk_ringbuffer.c:1208
Code: 07 80 c1 03 38 c1 0f 8c 75 ff ff ff 48 8b 3c 24 e8 24 b2 6b 00 e9 67 ff ff ff e8 6a 85 1a 00 eb 93 0f 1f 84 00 00 00 00 00 55 <41> 57 41 56 41 55 41 54 53 48 83 ec 20 49 89 d6 48 89 f3 48 89 fd
RSP: 0018:ffffc900032a79d0 EFLAGS: 00000202
RAX: 0000000000000401 RBX: ffffc900032a7c00 RCX: 0000000000000000
RDX: ffffc900032a7a78 RSI: ffffc900032a7ae8 RDI: ffffffff8ca45b10
RBP: ffffc900032a7b80 R08: ffffc900032a7c57 R09: 1ffff92000654f8a
R10: dffffc0000000000 R11: fffff52000654f8b R12: ffffffff8ca45ae0
R13: ffffc900032a7c00 R14: dffffc0000000000 R15: 0000000000000400
copy_data kernel/printk/printk_ringbuffer.c:1716 [inline]
prb_read kernel/printk/printk_ringbuffer.c:1825 [inline]
_prb_read_valid+0x5d8/0x9a0 kernel/printk/printk_ringbuffer.c:1891
prb_read_valid+0x39/0x60 kernel/printk/printk_ringbuffer.c:1940
syslog_print+0x31f/0x630 kernel/printk/printk.c:1543
do_syslog+0x817/0x900 kernel/printk/printk.c:1679
__do_sys_syslog kernel/printk/printk.c:1771 [inline]
__se_sys_syslog kernel/printk/printk.c:1769 [inline]
__x64_sys_syslog+0x78/0x90 kernel/printk/printk.c:1769
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f5540867a37
Code: 73 01 c3 48 8b 0d c1 f3 0c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 67 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 91 f3 0c 00 f7 d8 64 89 01 48
RSP: 002b:00007ffccff8fb68 EFLAGS: 00000206 ORIG_RAX: 0000000000000067
RAX: ffffffffffffffda RBX: 00007f5540a07490 RCX: 00007f5540867a37
RDX: 00000000000003ff RSI: 00007f5540a07490 RDI: 0000000000000002
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000004000 R11: 0000000000000206 R12: 00007f5540a07490
R13: 00007f55409e4dfe R14: 00007f5540a074f3 R15: 00007f5540a074f3
</TASK>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 6e2fd6534337 Linux 5.15.213
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1536f649580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f161cbc9aef65db0
dashboard link: https://syzkaller.appspot.com/bug?extid=7bd1e41e53a7d70b3df7

compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

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

Downloadable assets:

disk image: https://storage.googleapis.com/syzbot-assets/d7b46606b13d/disk-6e2fd653.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/da120fdeb081/vmlinux-6e2fd653.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3c2643457e3f/bzImage-6e2fd653.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:

Reported-by: syzbot+7bd1e4...@syzkaller.appspotmail.com

INFO: task getty:3944 blocked for more than 145 seconds.

Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

task:getty state:D stack:22288 pid: 3944 ppid: 1 flags:0x00004002
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11c3/0x4350 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
schedule_timeout+0xbd/0x2d0 kernel/time/timer.c:2093
do_wait_for_common+0x295/0x460 kernel/sched/completion.c:85

__wait_for_common kernel/sched/completion.c:106 [inline]
wait_for_common kernel/sched/completion.c:117 [inline]

wait_for_completion+0x48/0x60 kernel/sched/completion.c:138
__flush_work+0x15a/0x210 kernel/workqueue.c:3094
__cancel_work_timer+0x3f4/0x560 kernel/workqueue.c:3181
hci_unregister_dev+0x163/0x590 net/bluetooth/hci_core.c:4061
hci_uart_tty_close+0x268/0x330 drivers/bluetooth/hci_ldisc.c:575
tty_ldisc_reinit+0xe4/0x460 drivers/tty/tty_ldisc.c:679
tty_ldisc_hangup+0x360/0x4a0 drivers/tty/tty_ldisc.c:745
__tty_hangup+0x44e/0x670 drivers/tty/tty_io.c:639
disassociate_ctty+0x38d/0x860 drivers/tty/tty_jobctrl.c:275
do_exit+0x5f9/0x2110 kernel/exit.c:888
do_group_exit+0x12c/0x2f0 kernel/exit.c:1004
__do_sys_exit_group kernel/exit.c:1015 [inline]
__se_sys_exit_group kernel/exit.c:1013 [inline]
__x64_sys_exit_group+0x3b/0x40 kernel/exit.c:1013
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f98cf3e66c5
RSP: 002b:00007fff30bad188 EFLAGS: 00000202 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007f98cf4e7fe8 RCX: 00007f98cf3e66c5
RDX: 00000000000000e7 RSI: ffffffffffffff88 RDI: 0000000000000001
RBP: 0000000000000001 R08: 00007fff30bad118 R09: 0000000000000000
R10: 00007fff30bacfb0 R11: 0000000000000202 R12: 0000000000000000
R13: 0000000000000001 R14: 00007f98cf4e6680 R15: 00007f98cf4e8000

</TASK>

Showing all locks held in the system:

1 lock held by khungtaskd/27:

#0: ffffffff8c31ef60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
2 locks held by getty/3944:
#0: ffff88802c7641c0 (&tty->legacy_mutex){+.+.}-{3:3}, at: __tty_hangup+0xc0/0x670 drivers/tty/tty_io.c:599
#1: ffff88802c764098 (&tty->ldisc_sem){++++}-{0:0}, at: __tty_ldisc_lock drivers/tty/tty_ldisc.c:300 [inline]
#1: ffff88802c764098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_lock+0x68/0xb0 drivers/tty/tty_ldisc.c:324
4 locks held by kworker/u4:5/4241:
#0: ffff888076314938 ((wq_completion)phy14){+.+.}-{0:0}, at: process_one_work+0x75c/0xff0 kernel/workqueue.c:-1
#1: ffffc9000317fd00 ((work_completion)(&(&local->scan_work)->work)){+.+.}-{0:0}, at: process_one_work+0x79e/0xff0 kernel/workqueue.c:2285
#2: ffff888023cb2a28 (&local->mtx){+.+.}-{3:3}, at: ieee80211_scan_work+0x48/0x1aa0 net/mac80211/scan.c:1074
#3: ffffffff8c3239e8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:290 [inline]
#3: ffffffff8c3239e8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x2d1/0x750 kernel/rcu/tree_exp.h:845
2 locks held by kworker/0:20/7507:
#0: ffff888016c72138 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x75c/0xff0 kernel/workqueue.c:-1
#1: ffffc9000314fd00 ((work_completion)(&rew.rew_work)){+.+.}-{0:0}, at: process_one_work+0x79e/0xff0 kernel/workqueue.c:2285
3 locks held by kworker/u5:0/7973:
#0: ffff888074f85938 ((wq_completion)hci5){+.+.}-{0:0}, at: process_one_work+0x75c/0xff0 kernel/workqueue.c:-1
#1: ffffc90004a8fd00 ((work_completion)(&hdev->power_on)){+.+.}-{0:0}, at: process_one_work+0x79e/0xff0 kernel/workqueue.c:2285
#2: ffff888079d1d3f0 (&hdev->req_lock){+.+.}-{3:3}, at: hci_dev_do_open+0xa4/0x12a0 net/bluetooth/hci_core.c:1464
1 lock held by syz.6.1791/10546:
#0: ffffffff8c3238f0 (rcu_state.barrier_mutex){+.+.}-{3:3}, at: rcu_barrier+0xa1/0x4c0 kernel/rcu/tree.c:4043

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 27 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<TASK>

dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
nmi_cpu_backtrace+0x3a2/0x3d0 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:212 [inline]
watchdog+0xe1b/0xe60 kernel/hung_task.c:369
kthread+0x42e/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287