From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756849Ab1EYAQM (ORCPT ); Tue, 24 May 2011 20:16:12 -0400 Received: from e6.ny.us.ibm.com ([32.97.182.146]:46073 "EHLO e6.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752300Ab1EYAQL (ORCPT ); Tue, 24 May 2011 20:16:11 -0400 Date: Tue, 24 May 2011 17:16:08 -0700 From: "Paul E. McKenney" To: Yinghai Lu Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, hpa@zytor.com, tglx@linutronix.de, mingo@elte.hu Subject: Re: [tip:core/rcu] Revert "rcu: Decrease memory-barrier usage based on semi-formal proof" Message-ID: <20110525001608.GA21060@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <4DDAC01E.7050602@kernel.org> <20110523212530.GF7428@linux.vnet.ibm.com> <4DDAD934.9010603@kernel.org> <4DDAE5FA.2030303@kernel.org> <4DDAE6A5.6060701@kernel.org> <20110524011824.GL7428@linux.vnet.ibm.com> <4DDB093F.2060601@kernel.org> <20110524013523.GO7428@linux.vnet.ibm.com> <4DDC21E1.1070502@kernel.org> <20110525000530.GK2266@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110525000530.GK2266@linux.vnet.ibm.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 24, 2011 at 05:05:30PM -0700, Paul E. McKenney wrote: > On Tue, May 24, 2011 at 02:23:45PM -0700, Yinghai Lu wrote: > > On 05/23/2011 06:35 PM, Paul E. McKenney wrote: [ . . . ] > > after: > > commit bcd6e68330f893a81b3519ab3c5fc2bebbc9988c > > Author: Paul E. McKenney > > Date: Tue Sep 7 10:38:22 2010 -0700 > > > > rcu: Decrease memory-barrier usage based on semi-formal proof > > ... > > > > got: > > > > [ 32.447936] cpu_dev_init done > > [ 111.027066] memory_dev_init done > > So there is something nasty in this patch. > > Not seeing it immediately, but it does give me some focus for both > code inspection and possible diagnostic patches. Actually, I already do have some debugfs stuff that should help me spot the problem. So could you please build both with and without this commit enabling CONFIG_TRACE_RCU and send me the contents of the debugfs files rcu/rcuhier and rcu/rcudata in both cases? This will show me the results of the full boot path. If this turns out to drown out the differences, I will create a more focused diagnostic patch. Thanx, Paul