linux-kernel - Re: + proc-export-a-processes-resource-limits-via-proc-pid.patch added to -mm tree

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Message-ID: <20070817222228.GA783@tv-sign.ru>
Date:	Sat, 18 Aug 2007 02:22:28 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Neil Horman <nhorman@...driver.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: + proc-export-a-processes-resource-limits-via-proc-pid.patch added to -mm tree

Neil Horman wrote:
> 
> +static int proc_pid_limits(struct task_struct *task, char *buffer)
> +{
> +	unsigned int i;
> +	int count = 0;
> +	char *bufptr = buffer;
> +
> +	struct rlimit rlim[RLIM_NLIMITS];
> +
> +	read_lock(&tasklist_lock);
> +	memcpy(rlim, task->signal->rlim, sizeof(struct rlimit) * RLIM_NLIMITS);
> +	read_unlock(&tasklist_lock);

Please don't re-introduce tasklist_lock unless strictly needed. And in this case
it doesn't help, sys_getrlimit() changes ->rlim[] under task_lock().

Hovewer, I think the whole patch is not right. The "tsk" itself is pinned, but its
->signal is not stable and can be == NULL.

You can use lock_task_sighand() to access ->signal.

Oleg.

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