Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756584Ab3ENIVQ (ORCPT ); Tue, 14 May 2013 04:21:16 -0400 Received: from canardo.mork.no ([148.122.252.1]:41587 "EHLO canardo.mork.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754184Ab3ENIVM convert rfc822-to-8bit (ORCPT ); Tue, 14 May 2013 04:21:12 -0400 From: =?utf-8?Q?Bj=C3=B8rn_Mork?= To: "Srivatsa S. Bhat" 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 Organization: m 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> Date: Tue, 14 May 2013 10:20:50 +0200 In-Reply-To: <5191EBEF.4060409@linux.vnet.ibm.com> (Srivatsa S. Bhat's message of "Tue, 14 May 2013 13:16:55 +0530") Message-ID: <87ehdaezvh.fsf@nemi.mork.no> User-Agent: Gnus/5.11002 (No Gnus v0.20) Emacs/23.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2188 Lines: 58 "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. Thanks, Bjørn -- 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/