Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935346Ab3FSWl0 (ORCPT ); Wed, 19 Jun 2013 18:41:26 -0400 Received: from hydra.sisk.pl ([212.160.235.94]:43383 "EHLO hydra.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935028Ab3FSWlX (ORCPT ); Wed, 19 Jun 2013 18:41:23 -0400 From: "Rafael J. Wysocki" To: Xiaoguang Chen Cc: Viresh Kumar , Xiaoguang Chen , cpufreq@vger.kernel.org, linux-pm@vger.kernel.org, "linux-kernel@vger.kernel.org" , njiang1@marvell.com, zjwu@marvell.com, ylmao@marvell.com Subject: Re: [PATCH v5] cpufreq: fix governor start/stop race condition Date: Thu, 20 Jun 2013 00:50:44 +0200 Message-ID: <10398431.HfgFiK9AG8@vostro.rjw.lan> User-Agent: KMail/4.9.5 (Linux/3.10.0-rc5+; KDE/4.9.5; x86_64; ; ) In-Reply-To: References: <1371114118-19488-1-git-send-email-chenxg@marvell.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1578 Lines: 37 On Wednesday, June 19, 2013 11:26:13 AM Xiaoguang Chen wrote: > 2013/6/19 Viresh Kumar : > > On 19 June 2013 08:43, Viresh Kumar wrote: > >> On 19 June 2013 06:50, Xiaoguang Chen wrote: > >>> 2013/6/19 Rafael J. Wysocki : > >> > >>>>> 2) Current governor is userspace, now cpu0 hotplugs in cpu3, it will > >>>> > >>>> Can you please tell me what the above is supposed to mean? Is it supposed to > >>>> mean "the online of cpu3 is being run on cpu0" or something different? If > >>>> something different, then what? > > Sorry I missed this question, Let me explain it in detail > Suppose we are in such condtition, current cpufreq goveror is > userspace governor. cpu3 is offline. > and two things happen as above two cases, first thing is application > tries to change current governor to ondemand governor, > second thing is cpu0 tries to make cpu3 online which is off line > before. both of these two cases will try to stop current governor and > start a governor. if above two things interleave, unexpected behavior > will happen. Now it's clear, thanks for the explanation. [Well, I'll still need to fix up the changelog. Sigh.] Thanks, Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- 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/