linux-kernel - Re: odd timing bug with cgroups?

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Message-ID: <47364.1213416931@turing-police.cc.vt.edu>
Date:	Sat, 14 Jun 2008 00:15:31 -0400
From:	Valdis.Kletnieks@...edu
To:	Chris Friesen <cfriesen@...tel.com>
Cc:	linux-kernel@...r.kernel.org, vatsa@...ux.vnet.ibm.com,
	a.p.zijlstra@...llo.nl
Subject: Re: odd timing bug with cgroups?

On Fri, 13 Jun 2008 15:38:29 MDT, Chris Friesen said:

> This seems odd...I would think that as soon as the fork() call returns 
> in the parent we should be able to put that task into a group.

I'm admittedly shooting in the dark here, but remember that a successful
fork() call returns *twice*.  Just because the *parent* has returned
doesn't mean that the *child* has finished all the processing and returned
as well - it may be delayed by other kernel threads etc and still not quite
ready for tweaking.

It sounds like a variant of the race conditions we had a while back where
lots of programs blew chunks when we started having "child runs first"
semantics so children could run and exit before the parent was ready
for it?

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