From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751314Ab1AEBaE (ORCPT ); Tue, 4 Jan 2011 20:30:04 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:60365 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751141Ab1AEBaC (ORCPT ); Tue, 4 Jan 2011 20:30:02 -0500 Message-ID: <4D23C9B0.9060803@cn.fujitsu.com> Date: Wed, 05 Jan 2011 09:30:24 +0800 From: Lai Jiangshan User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.9) Gecko/20100921 Fedora/3.1.4-1.fc14 Thunderbird/3.1.4 MIME-Version: 1.0 To: paulmck@linux.vnet.ibm.com CC: Arnd Bergmann , Ingo Molnar , LKML Subject: Re: [PATCH] rcu: remove SPARSE_RCU_POINTER References: <4D22DD95.7050308@cn.fujitsu.com> <201101041136.02514.arnd@arndb.de> <20110104211938.GT2026@linux.vnet.ibm.com> In-Reply-To: <20110104211938.GT2026@linux.vnet.ibm.com> X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.1FP4|July 25, 2010) at 2011-01-05 09:29:41, Serialize by Router on mailserver/fnst(Release 8.5.1FP4|July 25, 2010) at 2011-01-05 09:29:42, Serialize complete at 2011-01-05 09:29:42 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/05/2011 05:19 AM, Paul E. McKenney wrote: > On Tue, Jan 04, 2011 at 11:36:02AM +0100, Arnd Bergmann wrote: >> On Tuesday 04 January 2011 09:43:01 Lai Jiangshan wrote: >>> As I known, __rcu annotations do not effect the result compiled kernel. >>> >>> They work only when we use spare("make C=1" or "make C=2"), >>> So we don't need another new switch for it since we have one >>> for debugging(use spare or not). >>> >>> signed-off-by: Lai Jiangshan >> >> The intention of this option was to avoid introducing an excessive >> number of false positives when using sparse. >> >> We should only make that unconditional if we are reasonably convinced >> that all the majority of warnings caused by it should actually >> lead to changes in the code. > > I agree with Arnd here -- the changes required are extensive in many > cases, and a number of subsystems are making decent progress. > > Thanx, Paul I also agree. Most guys like to use direct read to the rcu pointer on update side or direct read/write when initializing the rcu pointer. This causes a lot of false positives. Thanks, Lai