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	 <20090108183529.b4fd99f4.kamezawa.hiroyu@jp.fujitsu.com>
Date: Tue, 13 Jan 2009 18:48:43 -0800
Message-ID: <6599ad830901131848gf7f6996iead1276bc50753b8@mail.gmail.com>
Subject: Re: [RFC][PATCH 4/4] cgroup-memcg fix frequent EBUSY at rmdir
From: Paul Menage <menage@google.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
       "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
       "balbir@linux.vnet.ibm.com" <balbir@linux.vnet.ibm.com>,
       "nishimura@mxp.nes.nec.co.jp" <nishimura@mxp.nes.nec.co.jp>,
       "lizf@cn.fujitsu.com" <lizf@cn.fujitsu.com>
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On Thu, Jan 8, 2009 at 1:35 AM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@jp.fujitsu.com> wrote:
> +       if (ret == -EAGAIN) { /* subsys asks us to retry later */
> +               mutex_unlock(&cgroup_mutex);
> +               cond_resched();
> +               goto retry;
> +       }

This spinning worries me a bit. It might be better to do an
interruptible sleep until the relevant CSS's refcount goes down to
zero. And is there no way that the memory controller can hang on to a
reference indefinitely, if the cgroup still has some pages charged to
it?

Paul