From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932638AbZJGLEa (ORCPT ); Wed, 7 Oct 2009 07:04:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758873AbZJGLE3 (ORCPT ); Wed, 7 Oct 2009 07:04:29 -0400 Received: from mail-px0-f179.google.com ([209.85.216.179]:52735 "EHLO mail-px0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758879AbZJGLE2 convert rfc822-to-8bit (ORCPT ); Wed, 7 Oct 2009 07:04:28 -0400 MIME-Version: 1.0 In-Reply-To: References: <1254901778.30157.62.camel@eenurkka-desktop> <1254903263.30157.69.camel@eenurkka-desktop> <1254905013.30157.75.camel@eenurkka-desktop> <1254907901.30157.93.camel@eenurkka-desktop> Date: Wed, 7 Oct 2009 04:03:16 -0700 Message-ID: Subject: Re: [BISECTED] "conservative" cpufreq governor broken From: Steven Noonan To: Thomas Gleixner Cc: Eero Nurkkala , "linux-kernel@vger.kernel.org" , Rik van Riel , Venkatesh Pallipadi , Greg KH , Ingo Molnar Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 7, 2009 at 3:42 AM, Thomas Gleixner wrote: > On Wed, 7 Oct 2009, Eero Nurkkala wrote: >> For some reason, this path is taken: >> if (ts->nohz_mode == NOHZ_MODE_INACTIVE) >>         goto end; > > Well, probably because the machine never switched to NOHZ :) > >> > Also, this fix should probably be passed on to Greg K. H. (so it goes >> > in 2.6.31-stable) as well as Ingo Molnar (so it goes into -tip, and >> > hopefully to Linus for 2.6.32). Both CC'd. > > Don't worry, it'll go the right way. No need to cc the world and some > more :) > Sorry if it's not kosher. I was told that when dealing with a bisection you should CC: 1. those involved with a bisected patch (the Signed-off-by people), 2. those responsible for the affected subsystem (doing an author check via script[1]), 3. and those to whom a fix should be passed on to. Any tips so I don't bug the wrong people (or too many people) in the future? [1] http://www.uplinklabs.net/~tycho/linux/scripts/git-authors-email.sh (credits to Ingo for making this one. It's handy) >> >> From: Eero Nurkkala >> Date: Wed, 7 Oct 2009 11:54:26 +0300 >> Subject: [PATCH] NOHZ: update idle state properly >> >> Commit f2e21c9610991e95621a81407cdbab881226419b >> had unfortunate side effects with cpufreq governors on >> some systems. >> >> If NOHZ_MODE_INACTIVE was set, ts->inidle was not being >> set. Then, all subsequent calls from irq_exit() bypassed >> calls to tick_nohz_start_idle() which resulted in wrong >> information passed to cpufreq governors. Fix this by >> updating the state of ts->inidle where it fits the best. > > Hmm, nasty that code silently relies on NOHZ functionality even when > NOHZ is not active. That needs a big fat comment at least. > > Nice detective work though ! > > Thanks, > >        tglx >