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SubjectRe: cgroup: rmdir() does not complete
On Wed, 1 Sep 2010 12:10:23 +0100 (BST)
Mark Hills <mark@pogo.org.uk> wrote:

> On Fri, 27 Aug 2010, KAMEZAWA Hiroyuki wrote:
>
> > On Fri, 27 Aug 2010 12:39:48 +0900
> > Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:
> >
> > > On Fri, 27 Aug 2010 11:35:06 +0900
> > > KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> > >
> > > > On Fri, 27 Aug 2010 09:56:39 +0900
> > > > Daisuke Nishimura <nishimura@mxp.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 repeated the test above, but did not see a problem after many hundreds
> of loops.
>
> My test was with the same kernel from my original bug report (Fedora
> 2.6.33.6-147), using memory cgroup only and ext4 filesystem.
>
> So it is possible we are experiencing different bugs with similar
> symptoms.
>

Thank you for confirming.
But hmm...it's curious who holds mutex and what happens.

-Kame



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