From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751120AbVI1WLy (ORCPT ); Wed, 28 Sep 2005 18:11:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751123AbVI1WLy (ORCPT ); Wed, 28 Sep 2005 18:11:54 -0400 Received: from 22.107.233.220.exetel.com.au ([220.233.107.22]:10502 "EHLO arnor.apana.org.au") by vger.kernel.org with ESMTP id S1751120AbVI1WLx (ORCPT ); Wed, 28 Sep 2005 18:11:53 -0400 Date: Thu, 29 Sep 2005 08:11:10 +1000 To: "Paul E. McKenney" Cc: "David S. Miller" , suzannew@cs.pdx.edu, linux-kernel@vger.kernel.org, Robert.Olsson@data.slu.se, walpole@cs.pdx.edu, netdev@oss.sgi.com Subject: Re: [RFC][PATCH] identify in_dev_get rcu read-side critical sections Message-ID: <20050928221110.GA22018@gondor.apana.org.au> References: <20050927.135626.88296134.davem@davemloft.net> <20050928145110.GA4925@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050928145110.GA4925@us.ibm.com> User-Agent: Mutt/1.5.9i From: Herbert Xu Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 28, 2005 at 07:51:10AM -0700, Paul E. McKenney wrote: > > The reference-count approach is only guaranteed to work if the kernel > thread that did the reference-count increment is later referencing that > same data element. Otherwise, one has the following possible situation > on DEC Alpha: You're quite right. Without the rcu_dereference users of in_dev_get() may see pre-initialisation contents of in_dev. So these barriers are definitely needed. Thanks, -- Visit Openswan at http://www.openswan.org/ Email: Herbert Xu ~{PmV>HI~} Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt