linux-kernel - Re: [PATCH]: proc: export a processes resource limits via proc/<pid>

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Date:	Tue, 14 Aug 2007 01:04:02 +0400
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Neil Horman <nhorman@...driver.com>
Cc:	Ingo Oeser <ioe-lkml@...eria.de>, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, torvalds@...ux-foundation.org
Subject: Re: [PATCH]: proc: export a processes resource limits via proc/<pid>

On Mon, Aug 13, 2007 at 04:11:30PM -0400, Neil Horman wrote:
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -323,6 +324,68 @@ static int proc_oom_score(struct task_struct *task, char *buffer)
>  	return sprintf(buffer, "%lu\n", points);
>  }
>  
> +struct limit_names {
> +	char *name;
> +	char *unit;
> +};
> +
> +static const struct limit_names lnames[RLIM_NLIMITS] = {
> +	[RLIMIT_CPU] = {"Max cpu time", "ms"},
> +	[RLIMIT_FSIZE] = {"Max file size", "bytes"},
> +	[RLIMIT_DATA] = {"Max data size", "bytes"},
> +	[RLIMIT_STACK] = {"Max stack size", "bytes"},
> +	[RLIMIT_CORE] = {"Max core file size", "bytes"},
> +	[RLIMIT_RSS] = {"Max resident set", "bytes"},
> +	[RLIMIT_NPROC] = {"Max processes", "processes"},
> +	[RLIMIT_NOFILE] = {"Max open files", "files"},
> +	[RLIMIT_MEMLOCK] = {"Max locked memory", "bytes"},
> +	[RLIMIT_AS] = {"Max address space", "bytes"},
> +	[RLIMIT_LOCKS] = {"Max file locks", "locks"},
> +	[RLIMIT_SIGPENDING] = {"Max pending signals", "signals"},

this and processes should be left empty methinks, because max signals is
in fact unitless.

> +	[RLIMIT_MSGQUEUE] = {"Max msgqueue size", "bytes"},
> +	[RLIMIT_NICE] = {"Max nice priority", NULL},
> +	[RLIMIT_RTPRIO] = {"Max realtime priority", NULL},
> +};	

aha! trailing whitespace!

> +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));

unneeded (, )

> +	read_unlock(&tasklist_lock);

hmm, fork copies this under task lock of group leader and system calls
in sys.c too. What's up?

I'm sure it will give you nonsensical output because of wrong locks but
I haven't checked.

FWIW, it survived ~1 hour of cat /proc/*/limits, mini fork bombs, LTP,
gdb testsuite and one sooper sikrit proggie. on core2


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