From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759242Ab1EMNMY (ORCPT ); Fri, 13 May 2011 09:12:24 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:49531 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758584Ab1EMNMX (ORCPT ); Fri, 13 May 2011 09:12:23 -0400 Date: Fri, 13 May 2011 15:12:18 +0200 From: Ingo Molnar To: Yinghai Lu Cc: paulmck@linux.vnet.ibm.com, linux-kernel@vger.kernel.org Subject: Re: [GIT PULL rcu/next] rcu commits for 2.6.40 Message-ID: <20110513131218.GA7669@elte.hu> References: <4DCB157F.20202@kernel.org> <20110512060344.GB3191@elte.hu> <4DCB8BCD.1080607@kernel.org> <4DCB8F7A.90603@kernel.org> <20110512092013.GJ2258@linux.vnet.ibm.com> <4DCC52FB.6030500@kernel.org> <4DCC894D.3070204@kernel.org> <20110513084253.GE13647@elte.hu> <20110513121906.GA3676@elte.hu> <20110513130414.GA6863@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110513130414.GA6863@elte.hu> User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.3.1 -2.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Ingo Molnar wrote: > I started bisecting this, and the two relevant endpoints: > > bad: 11c476f: net,rcu: convert call_rcu(prl_entry_destroy_rcu) to kfree > good: 0ee5623f: Linux 2.6.39-rc6 > > very clearly indicate that this is an RCU regression. This might be the same one Yinghai found: e59fb3120bec: rcu: Decrease memory-barrier usage based on semi-formal proof So with the config i sent it's definitely reproducible. At first sight couldnt this be related not to barriers, but to not setting need_resched() like we did before? Thanks, Ingo