linux-kernel - Re: cgroup: rmdir() does not complete

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Message-Id: <20100827144225.3190167a.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Fri, 27 Aug 2010 14:42:25 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Cc:	Mark Hills <mark@...o.org.uk>, linux-kernel@...r.kernel.org,
	balbir@...ux.vnet.ibm.com
Subject: Re: cgroup: rmdir() does not complete

On Fri, 27 Aug 2010 12:39:48 +0900
Daisuke Nishimura <nishimura@....nes.nec.co.jp> wrote:

> On Fri, 27 Aug 2010 11:35:06 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:
> 
> > On Fri, 27 Aug 2010 09:56:39 +0900
> > Daisuke Nishimura <nishimura@....nes.nec.co.jp> wrote:
> > 
> > > > Or is it likely to be some other cause, and how best to find it?
> > > > 
> > > What cgroup subsystem did you mount where the directory existed you tried
> > > to rmdir() first ?
> > > If you mounted several subsystems on the same hierarchy, can you mount them
> > > separately to narrow down the cause ?
> > > 
> > 
> > It seems I can reproduce the issue on mmotm-0811, too.
> > 
> > try this.
> > 
> > Here, memory cgroup is mounted at /cgroups.
> > ==
> > #!/bin/bash -x
> > 
> > while sleep 1; do
> >         date
> >         mkdir /cgroups/test
> >         echo 0 > /cgroups/test/tasks
> >         echo 300M > /cgroups/test/memory.limit_in_bytes
> >         cat /proc/self/cgroup
> >         dd if=/dev/zero of=./tmpfile bs=4096 count=100000
> >         echo 0 > /cgroups/tasks
> >         cat /proc/self/cgroup
> >         rmdir /cgroups/test
> >         rm ./tmpfile
> > done
> > ==
> > 
> > hangs at rmdir. I'm no investigating force_empty.
> > 
> Thank you very much for your information.
> 
> Some questions.
> 
> Is "tmpfile" created on a normal filesystem(e.g. ext3) or tmpfs ?
on ext4.

> And, how long does it likely to take to cause this problem ?

very soon. 10-20 loop.

> I've run it on RHEL6-based kernel/ext3 for about one hour, but
> I cannot reproduce it yet.
> 

Hmm...I'll dig more. Maybe I need to use stock kernel rather than -mm...


Thanks,
-Kame

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