From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760051AbbA0WJO (ORCPT ); Tue, 27 Jan 2015 17:09:14 -0500 Received: from userp1040.oracle.com ([156.151.31.81]:29341 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755780AbbA0WJN (ORCPT ); Tue, 27 Jan 2015 17:09:13 -0500 Message-ID: <54C80C55.2070908@oracle.com> Date: Tue, 27 Jan 2015 17:08:21 -0500 From: Sasha Levin User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: paulmck@linux.vnet.ibm.com, Lai Jiangshan CC: Ingo Molnar , Peter Zijlstra , LKML , "davej@codemonkey.org.uk >> Dave Jones" Subject: Re: rcu, sched: WARNING: CPU: 30 PID: 23771 at kernel/rcu/tree_plugin.h:337 rcu_read_unlock_special+0x369/0x550() References: <20150122004305.GJ9719@linux.vnet.ibm.com> <54C1BFFD.9060707@oracle.com> <20150123035158.GP9719@linux.vnet.ibm.com> <54C1C7D2.906@oracle.com> <54C1C899.8000106@oracle.com> <20150123065542.GQ9719@linux.vnet.ibm.com> <20150123093644.GA11175@linux.vnet.ibm.com> <54C300DD.9070608@cn.fujitsu.com> <20150124211834.GD9719@linux.vnet.ibm.com> <54C5A184.20105@cn.fujitsu.com> <20150127220329.GF19109@linux.vnet.ibm.com> In-Reply-To: <20150127220329.GF19109@linux.vnet.ibm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Source-IP: ucsinet22.oracle.com [156.151.31.94] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/27/2015 05:03 PM, Paul E. McKenney wrote: > On Mon, Jan 26, 2015 at 10:08:04AM +0800, Lai Jiangshan wrote: >> > On 01/25/2015 05:18 AM, Paul E. McKenney wrote: >> > >>> > > >>> > > Good point! In my scenario, CPU 0 would not yet have switched away from >>> > > Task A. Hmmm... Yet Sasha really does see this failure. Will give it >>> > > some more thought. >>> > > >>> > > Any ideas? >> > >> > I don't known which commit was merged from the rcu-git-tree in Sasha's test >> > I try to review it. > If I had to guess, it would be 1d082fd06188 (Remove local_irq_disable() > in rcu_preempt_note_context_switch()), though his finding this might be > more directly related to increases in trinity's levels of stress. Quick update from my end: I've stopped seeing this warning, but I've also stopped seeing warnings for the other RCU issue I've reported (https://lkml.org/lkml/2015/1/22/676) so I'm slightly unhappy about that. >> > We can fallback to git-bitsect if the reviews fails. > One (very unlikely) possibility is that Sasha's compiler is ignoring the > barrier() in rcu_preempt_qs(). I'm actually running the latest gcc (trunk) as well, so it's very possible that it was doing something stupid. Thanks, Sasha