Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756613Ab3ENIYT (ORCPT ); Tue, 14 May 2013 04:24:19 -0400 Received: from e23smtp02.au.ibm.com ([202.81.31.144]:37142 "EHLO e23smtp02.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754184Ab3ENIYQ (ORCPT ); Tue, 14 May 2013 04:24:16 -0400 Message-ID: <5191F3FB.3080004@linux.vnet.ibm.com> Date: Tue, 14 May 2013 13:51:15 +0530 From: "Srivatsa S. Bhat" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120828 Thunderbird/15.0 MIME-Version: 1.0 To: =?UTF-8?B?QmrDuHJuIE1vcms=?= CC: paulmck@linux.vnet.ibm.com, Dipankar Sarma , linux-kernel@vger.kernel.org, rostedt@goodmis.org, Thomas Gleixner Subject: Re: [v3.10-rc1] WARNING: at kernel/rcutree.c:502 References: <87ip2opntp.fsf@nemi.mork.no> <20130512113905.GH3648@linux.vnet.ibm.com> <87li7kp50r.fsf@nemi.mork.no> <20130512172135.GJ3648@linux.vnet.ibm.com> <87a9o0ukll.fsf@nemi.mork.no> <87sj1rydol.fsf@nemi.mork.no> <87wqr3j656.fsf@nemi.mork.no> <519169BF.4080208@linux.vnet.ibm.com> <87ppwuroxb.fsf@nemi.mork.no> <5191EBEF.4060409@linux.vnet.ibm.com> <87ehdaezvh.fsf@nemi.mork.no> In-Reply-To: <87ehdaezvh.fsf@nemi.mork.no> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13051408-5490-0000-0000-00000376B0B0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2321 Lines: 65 On 05/14/2013 01:50 PM, Bjørn Mork wrote: > "Srivatsa S. Bhat" writes: >> On 05/14/2013 01:08 PM, Bjørn Mork wrote: >>> "Srivatsa S. Bhat" writes: >>> >>>> The problem appears to be in the cpu idle poll implementation. You can trigger >>>> this problem by passing idle=poll in the kernel cmd-line as well, right? >>> >>> That sounded so obvious that it made me think "Doh, why didn't I just >>> test that before?" But unfortunately there must be some other factor >>> involved. No warnings observed during normal use when running with >>> idle=poll: >>> >> >> I didn't expect warnings with normal use. >> >>> bjorn@nemi:~$ dmesg|grep polling >>> [ 0.000000] process: using polling idle threads >>> >>> >>> I expected a flood of warnings here, but there is none until I start >>> powertop (to confirm that the original issue is still there). So it's >>> more than just entering cpu_idle_poll(). >>> >> >> Yeah, of course it is :-) The warning triggers only when you enable the tracepoint >> in the idle code. And in your case, powertop does that. That's why it only >> triggers when you run powertop. Alternatively, if you enable the tracepoint >> yourself manually, I bet you'll see the warnings, even without using powertop. > > Ah, right. That sounds so obvious I have to go "Doh!" again:) > :-) >>>> I think I understand what is going on here. Can you please try the fix below? >>>> (It is only compile-tested since its very late here and I really need to get >>>> some sleep!). >>> >>> Works perfect. Thanks. >> >> Thanks for your testing! >> >>> I assume this is the correct fix even if the >>> problem isn't completely understood? >>> >> >> Hmm? Why do you say the problem isn't completely understood? I thought I >> explained the problem in my changelog. Did I miss something? > > No, I did. I didn't understand the tracepoint part of this. But it is > all perfectly clear to me too now, after your excellent explanation > above. > Great! Thanks :) Regards, Srivatsa S. Bhat -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/