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Message-ID: <28c262360808040736u7f364fc0p28d7ceea7303a626@mail.gmail.com>
Date: Mon, 4 Aug 2008 23:36:25 +0900
From: "MinChan Kim" <minchan.kim@gmail.com>
To: "KAMEZAWA Hiroyuki" <kamezawa.hiroyu@jp.fujitsu.com>,
       "Balbir Singh" <balbir@linux.vnet.ibm.com>
Subject: Race condition between putback_lru_page and mem_cgroup_move_list
Cc: linux-mm <linux-mm@kvack.org>, "Rik van Riel" <riel@redhat.com>,
       "KOSAKI Motohiro" <kosaki.motohiro@jp.fujitsu.com>,
       "Lee Schermerhorn" <lee.schermerhorn@hp.com>,
       LKML <linux-kernel@vger.kernel.org>
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I think this is a race condition if mem_cgroup_move_lists's comment isn't right.
I am not sure that it was already known problem.

mem_cgroup_move_lists assume the appropriate zone's lru lock is already held.
but putback_lru_page calls mem_cgroup_move_lists without holding lru_lock.

Repeatedly, spin_[un/lock]_irq use in mem_cgroup_move_list have a big overhead
while doing list iteration.

Do we have to use pagevec ?

-- 
Kinds regards,
MinChan Kim