linux-kernel - Re: [PATCH] hung_task: change sysctl_hung_task_check

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Message-ID: <5233CFBF.4000803@huawei.com>
Date:	Sat, 14 Sep 2013 10:53:51 +0800
From:	Li Zefan <lizefan@...wei.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH] hung_task: change sysctl_hung_task_check_count to int

Cc: Ingo, as this touched include/linux/sched/.

On 2013/9/14 10:47, Li Zefan wrote:
> As sysctl_hung_task_check_count is unsigned long, when this value is
> assigned to max_count in check_hung_uninterruptible_tasks(), it's
> truncated to int type.
> 
> Therefore if we write 2^32 to sysctl.hung_task_check_count, hung task
> detection will be effectively disabled.
> 
> Not a big deal, but still it's better to fix this inconsistency.
> 
> Signed-off-by: Li Zefan <lizefan@...wei.com>
> ---
>  include/linux/sched/sysctl.h | 2 +-
>  kernel/hung_task.c           | 2 +-
>  kernel/sysctl.c              | 4 ++--
>  3 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h
> index bf8086b..9552afa 100644
> --- a/include/linux/sched/sysctl.h
> +++ b/include/linux/sched/sysctl.h
> @@ -2,8 +2,8 @@
>  #define _SCHED_SYSCTL_H
>  
>  #ifdef CONFIG_DETECT_HUNG_TASK
> +extern int	     sysctl_hung_task_check_count;
>  extern unsigned int  sysctl_hung_task_panic;
> -extern unsigned long sysctl_hung_task_check_count;
>  extern unsigned long sysctl_hung_task_timeout_secs;
>  extern unsigned long sysctl_hung_task_warnings;
>  extern int proc_dohung_task_timeout_secs(struct ctl_table *table, int write,
> diff --git a/kernel/hung_task.c b/kernel/hung_task.c
> index 6df6149..b5a5d42 100644
> --- a/kernel/hung_task.c
> +++ b/kernel/hung_task.c
> @@ -19,7 +19,7 @@
>  /*
>   * The number of tasks checked:
>   */
> -unsigned long __read_mostly sysctl_hung_task_check_count = PID_MAX_LIMIT;
> +int __read_mostly sysctl_hung_task_check_count = PID_MAX_LIMIT;
>  
>  /*
>   * Limit number of tasks checked in a batch.
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 07f6fc4..5e5cc21 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -962,9 +962,9 @@ static struct ctl_table kern_table[] = {
>  	{
>  		.procname	= "hung_task_check_count",
>  		.data		= &sysctl_hung_task_check_count,
> -		.maxlen		= sizeof(unsigned long),
> +		.maxlen		= sizeof(int),
>  		.mode		= 0644,
> -		.proc_handler	= proc_doulongvec_minmax,
> +		.proc_handler	= proc_dointvec_minmax,
>  	},
>  	{
>  		.procname	= "hung_task_timeout_secs",
> 

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