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

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Date:	Wed, 3 Feb 2010 18:49:47 +0100
From:	Lennart Poettering <mzxreary@...inter.de>
To:	Américo Wang <xiyou.wangcong@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] exit: PR_SET_ANCHOR for marking processes as reapers
 	for child processes

On Wed, 03.02.10 23:31, Américo Wang (xiyou.wangcong@...il.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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