Date: Wed, 3 Feb 2010 18:49:47 +0100
From: Lennart Poettering <mzxreary@0pointer.de>
To: =?iso-8859-1?Q?Am=E9rico?= Wang <xiyou.wangcong@gmail.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] exit: PR_SET_ANCHOR for marking processes as reapers
 	for child processes
Message-ID: <20100203174947.GA13943@tango.0pointer.de>
References: <20100202120457.GA19605@omega>
 <20100203153101.GC4177@hack>
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On Wed, 03.02.10 23:31, Am?rico Wang (xiyou.wangcong@gmail.com) wrote:

> On Tue, Feb 02, 2010 at 01:04:57PM +0100, Lennart Poettering wrote:
> >
> >This patch adds a simple flag for each process that marks it as an
> >"anchor" process for all its children and grandchildren. If a child of
> >such an anchor dies all its children will not be reparented to init, but
> >instead to this anchor, escaping this anchor process is not possible. A
> >task with this flag set hence acts is little "sub-init".
> 
> This will break the applictions which using 'getppid() == 1' to check
> if its real parent is dead or not...

Usage of the PR_SETANCHOR flag is optional for a process. It won't
break anything unless enabled. So I don't really see a problem here.

Of course, when this flag is used the behaviour is different from what
traditional Unix says what happens with the children of a process when
it dies. But uh, that's the whole point and that's why this flag is
enabled optionally only.

Also, on a side note: code that checks if its parent process died most
likely should rewritten to use PR_DEATHSIG or something like that
anyway, so that it is notified about the parent dying instead of
polling for it manually.

Lennart

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