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SubjectRe: [PATCH v2] kernel/hung_task: add option to ignore task
On Wed, Sep 28, 2022 at 03:48:41PM +0800, Kassey Li wrote:
> By default, hung_task will iterate the tasklist and check
> state in TASK_UNINTERRUPTIBLE with a given timeout value.
>
> Here we add an option for task_struct so it can be ignored.
> Set this flag to default true, it do not break the origin design.
>
> This is useful when we set timeout value to 5s, where we just want
> to detect some tasks interested.
>
> Suggested-by: Naman Jain <quic_namajain@quicinc.com>
> Signed-off-by: Kassey Li <quic_yingangl@quicinc.com>
> ---
> include/linux/sched.h | 1 +
> kernel/fork.c | 1 +
> kernel/hung_task.c | 3 ++-
> 3 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index e7b2f8a5c711..7c8596fea1f6 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1071,6 +1071,7 @@ struct task_struct {
> #ifdef CONFIG_DETECT_HUNG_TASK
> unsigned long last_switch_count;
> unsigned long last_switch_time;
> + bool hung_task_detect;
> #endif
> /* Filesystem information: */
> struct fs_struct *fs;
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 90c85b17bf69..5c461a37a26e 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1552,6 +1552,7 @@ static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)
> #ifdef CONFIG_DETECT_HUNG_TASK
> tsk->last_switch_count = tsk->nvcsw + tsk->nivcsw;
> tsk->last_switch_time = 0;
> + tsk->hung_task_detect = 1;
> #endif
>
> tsk->mm = NULL;
> diff --git a/kernel/hung_task.c b/kernel/hung_task.c
> index bb2354f73ded..74bf4cef857f 100644
> --- a/kernel/hung_task.c
> +++ b/kernel/hung_task.c
> @@ -119,7 +119,8 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
> if (sysctl_hung_task_panic) {
> console_verbose();
> hung_task_show_lock = true;
> - hung_task_call_panic = true;
> + if (t->hung_task_detect)
> + hung_task_call_panic = true;
> }
>
> /*
> --
> 2.17.1
>

This patch does not seems to be complete. Do you plan to provide an interface
to set/clear task_struct::hung_task_detect? Please explain the motivation and
the problems solved by this interface.

Thanks,
Pavan

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