linux-kernel - Re: [PATCH 0/3] extend get/setrlimit to support setting rlimits external to a process (v7)

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Message-ID: <4AF84E2F.3010305@gmail.com>
Date:	Mon, 09 Nov 2009 18:15:27 +0100
From:	Jiri Slaby <jirislaby@...il.com>
To:	Oleg Nesterov <oleg@...hat.com>
CC:	Ingo Molnar <mingo@...e.hu>, Neil Horman <nhorman@...driver.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	marcin.slusarz@...il.com, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 0/3] extend get/setrlimit to support setting rlimits external
 to a process (v7)

On 11/09/2009 05:40 PM, Oleg Nesterov wrote:
> Also, I don't understand why wthis code get's both pid and task_struct().

And what do you suggest? I, with my knowledge and after fast
investigation, see no other option.

> And the "if (resource >= RLIM_NLIMITS)" check is racy afaics, see
> http://marc.info/?l=linux-kernel&m=125200862124872

Your patch (which I have in my series btw) is likely needed for the
setprlimit syscall, having this on my mind again from now on. But the
'if' above is a different story. 'resource' is an index here.

And as a bonus, what I found out now is that /proc/*/limits
(proc_info_read->proc_pid_limits) doesn't necessarily reflect current
limits. Since task_lock(current->group_leader) is not held, values of
one limit may be from the old as well as the currently updated one.

Am I right and do we care at all (since it's not atomic anyway in the
sense of reading 2 small chunks from that file)?

Thanks for the input.
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