linux-kernel - Re: + prctl-add-pr_set_proctitle_area-option.patch added to -mm tree

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Message-ID: <1257876016.3022.277.camel@timo-desktop>
Date:	Tue, 10 Nov 2009 13:00:16 -0500
From:	Timo Sirainen <tss@....fi>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Bryan Donlan <bdonlan@...il.com>,
	Ulrich Drepper <drepper@...hat.com>,
	WANG Cong <xiyou.wangcong@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: + prctl-add-pr_set_proctitle_area-option.patch added to -mm
 tree

On Wed, 2009-11-11 at 02:48 +0900, KOSAKI Motohiro wrote:
> There is unwritten reason. I hope to add /proc/[pid]/cmdline cache. It
> help to avoid
> ps getting stuck by mmap_sem.

Can you explain this further? When would it cache the value and when
would it be returned? I was at least hoping to avoid calling prctl()
every time when I want process title changed.

I think Solaris saves the first 80 chars of the initial cmdline to
kernel memory and gives that to ps. I guess doing something similar and
returning it only when userspace memory can't be accessed would be ok.

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