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

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Message-Id: <20100827123948.b4427a15.nishimura@mxp.nes.nec.co.jp>
Date:	Fri, 27 Aug 2010 12:39:48 +0900
From:	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Mark Hills <mark@...o.org.uk>, linux-kernel@...r.kernel.org,
	balbir@...ux.vnet.ibm.com,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Subject: Re: cgroup: rmdir() does not complete

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 ?
And, how long does it likely to take to cause this problem ?
I've run it on RHEL6-based kernel/ext3 for about one hour, but
I cannot reproduce it yet.


Thanks,
Daisuke Nishimura.
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