* Re: [Kernel Bug] INFO: task hung in cgroup_drain_dying
2026-06-09 12:58 ` Michal Koutný
@ 2026-06-10 7:11 ` Longxing Li
2026-06-10 13:27 ` Michal Koutný
0 siblings, 1 reply; 4+ messages in thread
From: Longxing Li @ 2026-06-10 7:11 UTC (permalink / raw)
To: Michal Koutný; +Cc: syzkaller, tj, hannes, cgroups, linux-kernel
sorry for not containing full information in last email. the config[1]
and report[2] are as follows. CONFIG_PROVE_LOCKING is not enabled in
our config.
[1] https://drive.google.com/file/d/1Bx2unEf-QntjVi8g6Zw7QNO6OP4cjGO_/view?usp=drive_link
[2] https://drive.google.com/file/d/1riFUIPWojkYVZu0B5BW8uVPocUWwibqN/view?usp=sharing
and report plain text is as follows:
INFO: task systemd:1 blocked for more than 143 seconds.
Not tainted 7.0.6 #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:systemd state:D stack:20616 pid:1 tgid:1 ppid:0
task_flags:0x400100 flags:0x00080001
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5298 [inline]
__schedule+0x1006/0x5f00 kernel/sched/core.c:6911
__schedule_loop kernel/sched/core.c:6993 [inline]
schedule+0xe7/0x3a0 kernel/sched/core.c:7008
cgroup_drain_dying+0x1ed/0x360 kernel/cgroup/cgroup.c:6294
cgroup_rmdir+0x38/0x300 kernel/cgroup/cgroup.c:6309
kernfs_iop_rmdir+0x10a/0x180 fs/kernfs/dir.c:1311
vfs_rmdir fs/namei.c:5344 [inline]
vfs_rmdir+0x340/0x860 fs/namei.c:5317
filename_rmdir+0x3be/0x510 fs/namei.c:5399
__do_sys_rmdir fs/namei.c:5422 [inline]
__se_sys_rmdir fs/namei.c:5419 [inline]
__x64_sys_rmdir+0x47/0x90 fs/namei.c:5419
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x11b/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb6c32a61c7
RSP: 002b:00007fff90d2bc98 EFLAGS: 00000202 ORIG_RAX: 0000000000000054
RAX: ffffffffffffffda RBX: 000055c177d80fb0 RCX: 00007fb6c32a61c7
RDX: 00007fb6c3387be0 RSI: 0000000000000000 RDI: 000055c177eb1300
RBP: 00007fb6c35eb2da R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000100 R11: 0000000000000202 R12: 0000000000000000
R13: 00007fb6c2ddb6c8 R14: 0000000000000001 R15: 0000000000000000
</TASK>
Showing all locks held in the system:
3 locks held by systemd/1:
#0: ffff8880294f8420 (sb_writers#10){.+.+}-{0:0}, at:
filename_rmdir+0x2cc/0x510 fs/namei.c:5388
#1: ffff888034d16e98 (&type->i_mutex_dir_key#6/1){+.+.}-{4:4}, at:
inode_lock_nested include/linux/fs.h:1073 [inline]
#1: ffff888034d16e98 (&type->i_mutex_dir_key#6/1){+.+.}-{4:4}, at:
__start_dirop fs/namei.c:2929 [inline]
#1: ffff888034d16e98 (&type->i_mutex_dir_key#6/1){+.+.}-{4:4}, at:
start_dirop fs/namei.c:2940 [inline]
#1: ffff888034d16e98 (&type->i_mutex_dir_key#6/1){+.+.}-{4:4}, at:
filename_rmdir+0x318/0x510 fs/namei.c:5392
#2: ffff8880386d7888 (&type->i_mutex_dir_key#6){++++}-{4:4}, at:
inode_lock include/linux/fs.h:1028 [inline]
#2: ffff8880386d7888 (&type->i_mutex_dir_key#6){++++}-{4:4}, at:
vfs_rmdir fs/namei.c:5329 [inline]
#2: ffff8880386d7888 (&type->i_mutex_dir_key#6){++++}-{4:4}, at:
vfs_rmdir+0xef/0x860 fs/namei.c:5317
6 locks held by kworker/u4:0/12:
3 locks held by kworker/u4:1/13:
1 lock held by khungtaskd/25:
#0: ffffffff8e5e6ce0 (rcu_read_lock){....}-{1:3}, at:
rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
#0: ffffffff8e5e6ce0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock
include/linux/rcupdate.h:850 [inline]
#0: ffffffff8e5e6ce0 (rcu_read_lock){....}-{1:3}, at:
debug_show_all_locks+0x36/0x1c0 kernel/locking/lockdep.c:6775
1 lock held by kcompactd0/28:
3 locks held by kworker/u4:3/45:
2 locks held by kworker/0:2/49:
3 locks held by kworker/u4:6/597:
3 locks held by kworker/u4:8/3491:
2 locks held by systemd-journal/5166:
2 locks held by systemd-udevd/5178:
1 lock held by in:imklog/9177:
4 locks held by sshd/9696:
2 locks held by syz-fuzzer/32911:
2 locks held by syz-executor.6/9754:
2 locks held by syz-executor.7/9774:
1 lock held by syz-executor.2/9812:
1 lock held by syz-executor.1/9902:
2 locks held by syz-executor.14/10080:
2 locks held by syz-executor.9/10842:
1 lock held by syz-executor.15/11893:
#0: ffffffff8e5f25f8 (rcu_state.exp_mutex){+.+.}-{4:4}, at:
exp_funnel_lock+0x1a3/0x3b0 kernel/rcu/tree_exp.h:343
3 locks held by kworker/0:8/13140:
#0: ffff88801b8a6948 ((wq_completion)events){+.+.}-{0:0}, at:
process_one_work+0x139e/0x1c60 kernel/workqueue.c:3263
#1: ffffc9000cd37d08 (free_ipc_work){+.+.}-{0:0}, at:
process_one_work+0x938/0x1c60 kernel/workqueue.c:3264
#2: ffffffff8e5f25f8 (rcu_state.exp_mutex){+.+.}-{4:4}, at:
exp_funnel_lock+0x1a3/0x3b0 kernel/rcu/tree_exp.h:343
2 locks held by kworker/0:10/13232:
3 locks held by kworker/u4:10/13343:
3 locks held by kworker/u4:12/14656:
1 lock held by syz-executor.13/24672:
3 locks held by kworker/u4:5/45131:
3 locks held by kworker/u4:9/46406:
3 locks held by kworker/u4:13/46990:
3 locks held by kworker/u4:16/46993:
2 locks held by syz-executor.8/48198:
3 locks held by kworker/u4:17/53143:
4 locks held by kworker/u4:18/53144:
2 locks held by systemd-rfkill/53174:
2 locks held by syz-executor.7/53471:
2 locks held by kworker/u4:20/53472:
3 locks held by kworker/u4:21/53476:
3 locks held by kworker/u4:22/53479:
3 locks held by kworker/u4:24/53484:
3 locks held by kworker/u4:25/53488:
2 locks held by kworker/0:19/53491:
2 locks held by systemd-udevd/53495:
=============================================
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 25 Comm: khungtaskd Not tainted 7.0.6 #1 PREEMPT(full)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1b0 lib/dump_stack.c:120
nmi_cpu_backtrace+0x2a0/0x350 lib/nmi_backtrace.c:113
nmi_trigger_cpumask_backtrace+0x29c/0x300 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:161 [inline]
__sys_info lib/sys_info.c:157 [inline]
sys_info+0x133/0x180 lib/sys_info.c:165
check_hung_uninterruptible_tasks kernel/hung_task.c:346 [inline]
watchdog+0xeac/0x11e0 kernel/hung_task.c:515
kthread+0x38d/0x4a0 kernel/kthread.c:436
ret_from_fork+0x942/0xe50 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
Michal Koutný <mkoutny@suse.com> 于2026年6月9日周二 20:58写道：
>
> Hello Longxing.
>
> On Tue, Jun 09, 2026 at 07:42:06PM +0800, Longxing Li <coregee2000@gmail.com> wrote:
> > We would like to report a new kernel bug found by our tool. INFO: task
> > hung in cgroup_drain_dying. Details are as follows.
>
> Thanks but I see no attachment.
>
> (Greater if you could add description as plaintext [1])
>
> > Kernel commit: v7.0.6
> > Kernel config: see attachment
>
> Do you have lockdep enabled (CONFIG_PROVE_LOCKING)? That may help
> debugging here.
>
> Thanks,
> Michal
>
> [1] https://docs.kernel.org/process/email-clients.html#general-preferences
>
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