Message-ID: <69533402.050a0220.329c0f.0428.GAE@google.com>
Date: Mon, 29 Dec 2025 18:08:02 -0800
From: syzbot <syzbot+05f9cecd28e356241aba@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, penguin-kernel@...ove.sakura.ne.jp, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [net?] INFO: task hung in new_device_store (5)

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
INFO: task hung in rtnl_lock

INFO: task kworker/u8:14:4104 blocked for more than 145 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u8:14   state:D
 stack:0     pid:4104  tgid:4104  ppid:2      task_flags:0x4208060 flags:0x00000010
Workqueue: ipv6_addrconf addrconf_dad_work
Call trace:
 __switch_to+0x418/0x87c arch/arm64/kernel/process.c:742 (T)
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x1250/0x2a7c kernel/sched/core.c:6863
 __schedule_loop kernel/sched/core.c:6945 [inline]
 schedule+0xb4/0x230 kernel/sched/core.c:6960
 schedule_preempt_disabled+0x18/0x2c kernel/sched/core.c:7017
 __mutex_lock_common+0xd04/0x2678 kernel/locking/mutex.c:692
 __mutex_lock kernel/locking/mutex.c:776 [inline]
 mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:828
 rtnl_lock+0x20/0x2c net/core/rtnetlink.c:80
 rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
 addrconf_dad_work+0x100/0x10cc net/ipv6/addrconf.c:4194
 process_one_work+0x7c0/0x1558 kernel/workqueue.c:3257
 process_scheduled_works kernel/workqueue.c:3340 [inline]
 worker_thread+0x958/0xed8 kernel/workqueue.c:3421
 kthread+0x5fc/0x75c kernel/kthread.c:463
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844
INFO: task kworker/0:3:6622 blocked for more than 149 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/0:3     state:D stack:0     pid:6622  tgid:6622  ppid:2      task_flags:0x4208060 flags:0x00000010
Workqueue: events reg_todo
Call trace:
 __switch_to+0x418/0x87c arch/arm64/kernel/process.c:742 (T)
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x1250/0x2a7c kernel/sched/core.c:6863
 __schedule_loop kernel/sched/core.c:6945 [inline]
 schedule+0xb4/0x230 kernel/sched/core.c:6960
 schedule_preempt_disabled+0x18/0x2c kernel/sched/core.c:7017
 __mutex_lock_common+0xd04/0x2678 kernel/locking/mutex.c:692
 __mutex_lock kernel/locking/mutex.c:776 [inline]
 mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:828
 class_wiphy_constructor include/net/cfg80211.h:6363 [inline]
 reg_process_self_managed_hints+0x98/0x1dc net/wireless/reg.c:3179
 reg_todo+0x81c/0x98c net/wireless/reg.c:3192
 process_one_work+0x7c0/0x1558 kernel/workqueue.c:3257
 process_scheduled_works kernel/workqueue.c:3340 [inline]
 worker_thread+0x958/0xed8 kernel/workqueue.c:3421
 kthread+0x5fc/0x75c kernel/kthread.c:463
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844

Showing all locks held in the system:
3 locks held by kworker/u8:0/12:
 #0: ffff0000c0031948 ((wq_completion)events_unbound#2
){+.+.}-{0:0}, at: raw_spin_rq_lock_nested kernel/sched/core.c:639 [inline]
){+.+.}-{0:0}, at: raw_spin_rq_lock kernel/sched/sched.h:1558 [inline]
){+.+.}-{0:0}, at: rq_lock kernel/sched/sched.h:1885 [inline]
){+.+.}-{0:0}, at: __schedule+0x370/0x2a7c kernel/sched/core.c:6768
 #1: ffff00019bc0c588 (psi_seq){-.-.}-{0:0}, at: psi_task_switch+0x6c/0x6dc kernel/sched/psi.c:933
 #2: ffff00019bc0de98 (&base->lock){-.-.}-{2:2}, at: lock_timer_base kernel/time/timer.c:1004 [inline]
 #2: ffff00019bc0de98 (&base->lock){-.-.}-{2:2}, at: __mod_timer+0x19c/0xd00 kernel/time/timer.c:1085
2 locks held by kworker/u8:1/13:
 #0: ffff0000d5d53948 ((wq_completion)bat_events){+.+.}-{0:0}, at: process_one_work+0x63c/0x1558 kernel/workqueue.c:3231
 #1: ffff800097d07be0 ((work_completion)(&(&bat_priv->tt.work)->work)){+.+.}-{0:0}, at: process_one_work+0x6d0/0x1558 kernel/workqueue.c:3231
1 lock held by khungtaskd/32:
 #0: ffff80008fa5b5a0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire+0x4/0x48 include/linux/rcupdate.h:330
2 locks held by kworker/u8:3/42:
 #0: ffff0000c0032148 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: process_one_work+0x63c/0x1558 kernel/workqueue.c:3231
 #1: ffff800097ff7be0 ((work_completion)(&(&gc_work->dwork)->work)){+.+.}-{0:0}, at: process_one_work+0x6d0/0x1558 kernel/workqueue.c:3231
3 locks held by kworker/u8:6/713:
 #0: ffff0000c0032148 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: process_one_work+0x63c/0x1558 kernel/workqueue.c:3231
 #1: ffff80009da57be0 ((crda_timeout).work){+.+.}-{0:0}, at: process_one_work+0x6d0/0x1558 kernel/workqueue.c:3231
 #2: ffff800092ae45e8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock+0x20/0x2c net/core/rtnetlink.c:80
3 locks held by kworker/u8:7/1561:
 #0: ffff0000c0031948 ((wq_completion)events_unbound#2){+.+.}-{0:0}, at: process_one_work+0x63c/0x1558 kernel/workqueue.c:3231
 #1: ffff8000a0627be0 ((work_completion)(&rdev->wiphy_work)){+.+.}-{0:0}, at: process_one_work+0x6d0/0x1558 kernel/workqueue.c:3231


Tested on:

commit:         8640b745 Merge tag 'kbuild-fixes-6.19-1' of git://git...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1664c422580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8a8594efdc14f07a
dashboard link: https://syzkaller.appspot.com/bug?extid=05f9cecd28e356241aba
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
userspace arch: arm64
patch:          https://syzkaller.appspot.com/x/patch.diff?x=149bbb92580000

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