From: Balbir Singh <balbir@linux.vnet.ibm.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
Pavel Emelyanov <xemul@openvz.org>,
Li Zefan <lizf@cn.fujitsu.com>, Paul Menage <menage@google.com>
Subject: Re: [RFC][PATCH 5/4] memcg: don't call res_counter_uncharge when obsolete
Date: Thu, 15 Jan 2009 09:47:50 +0530 [thread overview]
Message-ID: <20090115041750.GE21516@balbir.in.ibm.com> (raw)
In-Reply-To: <20090115122416.e15d88a7.kamezawa.hiroyu@jp.fujitsu.com>
* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-01-15 12:24:16]:
> On Wed, 14 Jan 2009 19:25:39 +0530
> Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
>
> > * Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> [2009-01-14 17:51:21]:
> >
> > > This is a new one. Please review.
> > >
> > > ===
> > > From: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> > >
> > > mem_cgroup_get ensures that the memcg that has been got can be accessed
> > > even after the directory has been removed, but it doesn't ensure that parents
> > > of it can be accessed: parents might have been freed already by rmdir.
> > >
> > > This causes a bug in case of use_hierarchy==1, because res_counter_uncharge
> > > climb up the tree.
> > >
> > > Check if the memcg is obsolete, and don't call res_counter_uncharge when obsole.
> > >
> > > Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> >
> > I liked the earlier, EBUSY approach that ensured that parents could
> > not go away if children exist. IMHO, the code has gotten too complex
> > and has too many corner cases. Time to revisit it.
> >
>
> But I don't like -EBUSY ;)
>
> When rmdir() returns -EBUSY even if there are no (visible) children and tasks,
> our customer will take kdump and send it to me "please explain this kernel bug"
>
> I'm sure it will happen ;)
>
OK, but memory.stat can show why the group is busy and with
move_to_parent() such issues should not occur right? I'll relook at
the code. Thanks for your input.
--
Balbir
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next prev parent reply other threads:[~2009-01-15 4:17 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-01-13 9:45 [PATCH -rc] some fixes for memcg Daisuke Nishimura
2009-01-13 9:47 ` [PATCH 1/4] memcg: fix mem_cgroup_get_reclaim_stat_from_page Daisuke Nishimura
2009-01-13 9:48 ` [PATCH 2/4] memcg: fix error path of mem_cgroup_move_parent Daisuke Nishimura
2009-01-13 9:49 ` [PATCH 3/4] memcg: fix hierarchical reclaim Daisuke Nishimura
2009-01-13 9:50 ` [PATCH 4/4] memcg: make oom less frequently Daisuke Nishimura
2009-01-14 8:51 ` [RFC][PATCH 5/4] memcg: don't call res_counter_uncharge when obsolete Daisuke Nishimura
2009-01-14 13:43 ` KAMEZAWA Hiroyuki
2009-01-15 1:03 ` Daisuke Nishimura
2009-01-15 2:00 ` KAMEZAWA Hiroyuki
2009-01-15 2:14 ` Daisuke Nishimura
2009-01-15 4:38 ` Daisuke Nishimura
2009-01-15 5:14 ` KAMEZAWA Hiroyuki
2009-01-15 5:49 ` Balbir Singh
2009-01-15 6:39 ` KAMEZAWA Hiroyuki
2009-01-15 7:45 ` [RFC][PATCH] memcg: get/put parents at create/free Daisuke Nishimura
2009-01-15 7:54 ` KAMEZAWA Hiroyuki
2009-01-15 8:13 ` Daisuke Nishimura
2009-01-15 8:23 ` KAMEZAWA Hiroyuki
2009-01-15 8:51 ` Daisuke Nishimura
2009-01-15 9:10 ` KAMEZAWA Hiroyuki
2009-01-16 1:50 ` [BUGFIX][PATCH] " Daisuke Nishimura
2009-01-16 2:12 ` Andrew Morton
2009-01-16 2:17 ` KAMEZAWA Hiroyuki
2009-01-16 2:25 ` Daisuke Nishimura
2009-01-16 4:22 ` Daisuke Nishimura
2009-01-16 4:31 ` KAMEZAWA Hiroyuki
2009-01-14 13:55 ` [RFC][PATCH 5/4] memcg: don't call res_counter_uncharge when obsolete Balbir Singh
2009-01-15 2:48 ` KAMEZAWA Hiroyuki
2009-01-15 3:08 ` KAMEZAWA Hiroyuki
2009-01-15 3:24 ` KAMEZAWA Hiroyuki
2009-01-15 4:17 ` Balbir Singh [this message]
2009-01-15 4:41 ` KAMEZAWA Hiroyuki
2009-01-15 4:45 ` Balbir Singh
2009-01-15 4:54 ` KAMEZAWA Hiroyuki
2009-01-15 4:52 ` KAMEZAWA Hiroyuki
2009-01-15 5:17 ` Balbir Singh
2009-01-15 5:27 ` KAMEZAWA Hiroyuki
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