linux-kernel - Re: [PATCH] include children count, in Threads: field present in /proc/<pid>/status (take-3)

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Message-ID: <m1mz8ii8wj.fsf@ebiederm.dsl.xmission.com>
Date:	Fri, 29 Sep 2006 16:51:24 -0600
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	girish <girishvg@...il.com>
Cc:	Jan Engelhardt <jengelh@...ux01.gwdg.de>,
	linux-kernel@...r.kernel.org, William Pitcock <nenolod@...eme.org>
Subject: Re: [PATCH] include children count, in Threads: field present in /proc/<pid>/status (take-3)


This conflicts with the /proc changes in -mm.
Where we have manged to remove the use of the tasklist_lock.

The information in Children: is racy as it may change immediately
after you drop the lock.

Why is it interesting to report this information?
A process that cares can keep track of this in user space?

Eric

> Signed-off-by: Girish V. Gulawani <girishvg@...il.com>
>
> --- linux-vanilla/fs/proc/array.c	2006-09-20 12:42:06.000000000 +0900
> +++ linux/fs/proc/array.c	2006-09-30 03:18:28.000000000 +0900
> @@ -248,6 +248,8 @@ static inline char * task_sig(struct tas
>  	int num_threads = 0;
>  	unsigned long qsize = 0;
>  	unsigned long qlim = 0;
> +	int num_children = 0;
> +	struct list_head *_p;
>
>  	sigemptyset(&pending);
>  	sigemptyset(&shpending);
> @@ -268,9 +270,13 @@ static inline char * task_sig(struct tas
>  		qlim = p->signal->rlim[RLIMIT_SIGPENDING].rlim_cur;
>  		spin_unlock_irq(&p->sighand->siglock);
>  	}
> +	list_for_each(_p, &p->children)
> +		++num_children;
>  	read_unlock(&tasklist_lock);
>
>  	buffer += sprintf(buffer, "Threads:\t%d\n", num_threads);
> +	if (num_children)
> +		buffer += sprintf(buffer, "Children:\t%d\nTotal:\t%d\n",
> num_children, num_threads + num_children);
>  	buffer += sprintf(buffer, "SigQ:\t%lu/%lu\n", qsize, qlim);
>
>  	/* render them all */
>
> -
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