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References: <20240321082850.1756-1-qiang.zhang1211@gmail.com>
In-Reply-To: <20240321082850.1756-1-qiang.zhang1211@gmail.com>
From: Z qiang <qiang.zhang1211@gmail.com>
Date: Thu, 21 Mar 2024 16:32:09 +0800
Message-ID: <CALm+0cXceF+-FR2oDu9YWrKrtRjwyomH7_rk=XdUJxQJFj4gaw@mail.gmail.com>
Subject: Re: [PATCH] rcutorture: Make stall-tasks directly exit when
 rcutorture tests end
To: paulmck@kernel.org, frederic@kernel.org, neeraj.upadhyay@kernel.org, 
	joel@joelfernandes.org
Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"

>
> When the rcutorture tests start to exit, the rcu_torture_cleanup() is
> invoked to stop kthreads and release resources, if the stall-task
> kthreads exist, cpu-stall has started and the rcutorture.stall_cpu
> is set to a larger value, the rcu_torture_cleanup() will be blocked
> for a long time and the hung-task may occur, this commit therefore
> add kthread_should_stop() to the loop of cpu-stall operation, when
> rcutorture tests ends, no need to wait for cpu-stall to end, exit
> directly.
>
> Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
> ---


Use the following command to test:

insmod rcutorture.ko torture_type=srcu fwd_progress=0 stat_interval=4
stall_cpu_block=1 stall_cpu=200 stall_cpu_holdoff=10 read_exit_burst=0
object_debug=1
rmmod rcutorture

[15361.918610] INFO: task rmmod:878 blocked for more than 122 seconds.
[15361.918613]       Tainted: G        W
6.8.0-rc2-yoctodev-standard+ #25
[15361.918615] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
disables this message.
[15361.918616] task:rmmod           state:D stack:0     pid:878
tgid:878   ppid:773    flags:0x00004002
[15361.918621] Call Trace:
[15361.918623]  <TASK>
[15361.918626]  __schedule+0xc0d/0x28f0
[15361.918631]  ? __pfx___schedule+0x10/0x10
[15361.918635]  ? rcu_is_watching+0x19/0xb0
[15361.918638]  ? schedule+0x1f6/0x290
[15361.918642]  ? __pfx_lock_release+0x10/0x10
[15361.918645]  ? schedule+0xc9/0x290
[15361.918648]  ? schedule+0xc9/0x290
[15361.918653]  ? trace_preempt_off+0x54/0x100
[15361.918657]  ? schedule+0xc9/0x290
[15361.918661]  schedule+0xd0/0x290
[15361.918665]  schedule_timeout+0x56d/0x7d0
[15361.918669]  ? debug_smp_processor_id+0x1b/0x30
[15361.918672]  ? rcu_is_watching+0x19/0xb0
[15361.918676]  ? __pfx_schedule_timeout+0x10/0x10
[15361.918679]  ? debug_smp_processor_id+0x1b/0x30
[15361.918683]  ? rcu_is_watching+0x19/0xb0
[15361.918686]  ? wait_for_completion+0x179/0x4c0
[15361.918690]  ? __pfx_lock_release+0x10/0x10
[15361.918693]  ? __kasan_check_write+0x18/0x20
[15361.918696]  ? wait_for_completion+0x9d/0x4c0
[15361.918700]  ? _raw_spin_unlock_irq+0x36/0x50
[15361.918703]  ? wait_for_completion+0x179/0x4c0
[15361.918707]  ? _raw_spin_unlock_irq+0x36/0x50
[15361.918710]  ? wait_for_completion+0x179/0x4c0
[15361.918714]  ? trace_preempt_on+0x54/0x100
[15361.918718]  ? wait_for_completion+0x179/0x4c0
[15361.918723]  wait_for_completion+0x181/0x4c0
[15361.918728]  ? __pfx_wait_for_completion+0x10/0x10
[15361.918738]  kthread_stop+0x152/0x470
[15361.918742]  _torture_stop_kthread+0x44/0xc0 [torture
7af7f9cbba28271a10503b653f9e05d518fbc8c3]
[15361.918752]  rcu_torture_cleanup+0x2ac/0xe90 [rcutorture
f2cb1f556ee7956270927183c4c2c7749a336529]
[15361.918766]  ? __pfx_rcu_torture_cleanup+0x10/0x10 [rcutorture
f2cb1f556ee7956270927183c4c2c7749a336529]
[15361.918777]  ? __kasan_check_write+0x18/0x20
[15361.918781]  ? __mutex_unlock_slowpath+0x17c/0x670
[15361.918789]  ? __might_fault+0xcd/0x180
[15361.918793]  ? find_module_all+0x104/0x1d0
[15361.918799]  __x64_sys_delete_module+0x2a4/0x3f0
[15361.918803]  ? __pfx___x64_sys_delete_module+0x10/0x10
[15361.918807]  ? syscall_exit_to_user_mode+0x149/0x280

Thanks
Zqiang


>  kernel/rcu/rcutorture.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
> index 3f9c3766f52b..6a3cd6ed8b25 100644
> --- a/kernel/rcu/rcutorture.c
> +++ b/kernel/rcu/rcutorture.c
> @@ -2490,7 +2490,7 @@ static int rcu_torture_stall(void *args)
>                 pr_alert("%s start on CPU %d.\n",
>                           __func__, raw_smp_processor_id());
>                 while (ULONG_CMP_LT((unsigned long)ktime_get_seconds(),
> -                                   stop_at))
> +                                   stop_at) && !kthread_should_stop())
>                         if (stall_cpu_block) {
>  #ifdef CONFIG_PREEMPTION
>                                 preempt_schedule();
> --
> 2.17.1
>