linux-kernel - Re: [PATCH] exit: PR_SET_ANCHOR for marking processes as reapers for child processes

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Message-ID: <20100306002414.GJ28657@tango.0pointer.de>
Date:	Sat, 6 Mar 2010 01:24:14 +0100
From:	Lennart Poettering <mzxreary@...inter.de>
To:	Roland McGrath <roland@...hat.com>
Cc:	Kay Sievers <kay.sievers@...y.org>,
	Oleg Nesterov <oleg@...hat.com>, linux-kernel@...r.kernel.org,
	Americo Wang <xiyou.wangcong@...il.com>,
	James Morris <jmorris@...ei.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Kyle McMartin <kyle@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Michael Kerrisk <mtk.manpages@...glemail.com>
Subject: Re: [PATCH] exit: PR_SET_ANCHOR for marking processes as reapers
 for  	child processes

On Fri, 05.03.10 11:18, Roland McGrath (roland@...hat.com) wrote:

> 
> > Oh, no. Actually getting the SIGCHILD is the needed feature here. A
> > process who sets the ANCHOR flag is surely expected to handle these
> > signals. It's all about a user "init-like" process" that can do
> > similar things for a logged-in user what /sbin/init can to for the
> > system. So, it's all about 1.), and 3.) is a nice side-effect, but not
> > the motivation to do this.
> 
> Please explain this more explicitly.  What the actual init does with
> miscellaneous reparented processes is just reap them and ignore their
> status.  What do you intend an "anchor" process to do other than that?

It could use the grandchildren's SIGCHLDs for various task management
issues: i.e. watching double-forking daemons, catch SIGSEGVS so that you
can crosslink that service state to systems like abrt. Or even just that
you can implement a safe restarting logic: i.e. so that we can easily
wait that a process and its children are fully dead before we restart
the service.

Lennart

-- 
Lennart Poettering                        Red Hat, Inc.
lennart [at] poettering [dot] net
http://0pointer.net/lennart/           GnuPG 0x1A015CC4
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