Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752990Ab0DMPRf (ORCPT ); Tue, 13 Apr 2010 11:17:35 -0400 Received: from mx1.redhat.com ([209.132.183.28]:24049 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752157Ab0DMPRe (ORCPT ); Tue, 13 Apr 2010 11:17:34 -0400 Date: Tue, 13 Apr 2010 11:16:45 -0400 From: Vivek Goyal To: Balbir Singh Cc: KAMEZAWA Hiroyuki , Randy Dunlap , "linux-mm@kvack.org" , "akpm@linux-foundation.org" , "nishimura@mxp.nes.nec.co.jp" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] memcg: update documentation v5 Message-ID: <20100413151645.GC4493@redhat.com> References: <20100408145800.ca90ad81.kamezawa.hiroyu@jp.fujitsu.com> <20100409134553.58096f80.kamezawa.hiroyu@jp.fujitsu.com> <20100409100430.7409c7c4.randy.dunlap@oracle.com> <20100413134553.7e2c4d3d.kamezawa.hiroyu@jp.fujitsu.com> <20100413135718.GA4493@redhat.com> <20100413140302.GB4493@redhat.com> <20100413150843.GI3994@balbir.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100413150843.GI3994@balbir.in.ibm.com> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1518 Lines: 47 On Tue, Apr 13, 2010 at 08:38:43PM +0530, Balbir Singh wrote: > * Vivek Goyal [2010-04-13 10:03:02]: > > > On Tue, Apr 13, 2010 at 09:57:18AM -0400, Vivek Goyal wrote: > > > On Tue, Apr 13, 2010 at 01:45:53PM +0900, KAMEZAWA Hiroyuki wrote: > > > > > > > Typed wrong email id last time and mail bounced. So here is another > > attempt. > > > > > [..] > > > > -2. Locking > > > > +2.6 Locking > > > > > > > > -The memory controller uses the following hierarchy > > > > + lock_page_cgroup()/unlock_page_cgroup() should not be called under > > > > + mapping->tree_lock. > > > > > > > > > > Because I never understood very well, I will ask. Why lock_page_cgroup() > > > should not be called under mapping->tree_lock? > > > > > The closest reference I can find to a conversation regarding this is > > http://linux.derkeiler.com/Mailing-Lists/Kernel/2009-05/msg05158.html > Thanks Balbir. So basically idea is that page_cgroup_lock() does not disable interrupts hence can be interrupted. So don't do lock_page_cgroup() in interrupt context at all otherwise it can lead to various kind of deadlock scenarios. One of those scenarios is lock_page_cgroup() under mapping->tree_lock. That helps. Thanks Vivek > -- > Three Cheers, > Balbir -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/