From: Balbir Singh <balbir@linux.vnet.ibm.com>
To: Hiroyuki Kamezawa <kamezawa.hiroyuki@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"nishimura@mxp.nes.nec.co.jp" <nishimura@mxp.nes.nec.co.jp>,
gthelen@google.com,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
stable@kernel.org
Subject: Re: [BUGFIX][PATCH] memcg: fix race in file_mapped accouting flag management
Date: Mon, 13 Sep 2010 22:47:41 +0530 [thread overview]
Message-ID: <20100913171741.GM17950@balbir.in.ibm.com> (raw)
In-Reply-To: <AANLkTimsUQuEeS2QvSwY_WhnQY7n=D73fNmOoqgrTqbZ@mail.gmail.com>
* Hiroyuki Kamezawa <kamezawa.hiroyuki@gmail.com> [2010-09-14 00:28:30]:
> > In the situation above who has the PTE lock? Are we not synchronized
> > via the PTE lock such that add rmap and rm rmap, will not happen
> > simultaneously?
> >
> In this case, a process for map and one for unmap can be different.
>
> Assume process A maps a file cache and process B not.
> While process A unmap a file, process B can map it.
> pte lock is no help.
>
Correct, so while the accounting is correct, the flag can definitely
go wrong. I misread your race description earlier.
Thanks!
--
Three Cheers,
Balbir
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next prev parent reply other threads:[~2010-09-13 17:17 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-13 7:08 KAMEZAWA Hiroyuki
2010-09-13 7:13 ` [PATCH] " KAMEZAWA Hiroyuki
2010-09-13 8:01 ` [PATCH] memcg: avoid lock in updating file_mapped (Was " KAMEZAWA Hiroyuki
2010-09-13 17:26 ` Balbir Singh
2010-09-14 4:55 ` KAMEZAWA Hiroyuki
2010-09-13 8:47 ` [BUGFIX][PATCH] memcg: " Balbir Singh
2010-09-13 15:28 ` Hiroyuki Kamezawa
2010-09-13 17:17 ` Balbir Singh [this message]
2010-09-13 21:08 ` Andrew Morton
2010-09-14 4:35 ` KAMEZAWA Hiroyuki
2010-09-14 4:38 ` KAMEZAWA Hiroyuki
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