From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751594Ab1JJPQy (ORCPT ); Mon, 10 Oct 2011 11:16:54 -0400 Received: from e23smtp02.au.ibm.com ([202.81.31.144]:46194 "EHLO e23smtp02.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751306Ab1JJPQw (ORCPT ); Mon, 10 Oct 2011 11:16:52 -0400 Message-ID: <4E930C53.3010309@linux.vnet.ibm.com> Date: Mon, 10 Oct 2011 20:46:35 +0530 From: "Srivatsa S. Bhat" User-Agent: Mozilla/5.0 (X11; Linux i686; rv:7.0) Gecko/20110927 Thunderbird/7.0 MIME-Version: 1.0 To: Peter Zijlstra CC: rjw@sisk.pl, bp@amd64.org, pavel@ucw.cz, len.brown@intel.com, tj@kernel.org, mingo@elte.hu, akpm@linux-foundation.org, suresh.b.siddha@intel.com, lucas.demarchi@profusion.mobi, rusty@rustcorp.com.au, rdunlap@xenotime.net, vatsa@linux.vnet.ibm.com, ashok.raj@intel.com, tigran@aivazian.fsnet.co.uk, tglx@linutronix.de, hpa@zytor.com, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org Subject: Re: [PATCH v2 2/3] Mutually exclude cpu online and suspend/hibernate References: <20111010123102.15067.23128.stgit@srivatsabhat.in.ibm.com> <20111010123242.15067.48238.stgit@srivatsabhat.in.ibm.com> <4E92E8E0.4090004@linux.vnet.ibm.com> <1318256788.14400.53.camel@laptop> In-Reply-To: <1318256788.14400.53.camel@laptop> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/10/2011 07:56 PM, Peter Zijlstra wrote: > On Mon, 2011-10-10 at 18:15 +0530, Srivatsa S. Bhat wrote: >>> + /* >>> + * Prevent cpu online and suspend/hibernate (including freezer) >>> + * operations from running in parallel. Fail cpu online if suspend or >>> + * hibernate has already started. >>> + */ >>> + if (!trylock_pm_sleep()) >> >> Would it be better to hook into the suspend/hibernate notifiers and >> use them to exclude cpu hotplug from suspend/hibernate, instead of >> trying to take pm_mutex lock like this? >> Peter, I remember you pointing out in another patch's review >> (http://thread.gmane.org/gmane.linux.kernel/1198312/focus=1199087) >> that introducing more locks in cpu hotplug would be a bad idea. Does that >> comment hold here as well, or is this fine? > > Arguably pm_mutex is already involved in the whole hotplug dance due to > suspend using it, that said, I'm not at all familiar with the whole > suspend/hibernate side of things. > > I tried having a quick look this morning but failed to find the actual > code. > > I think it would be good to have an overview of the various locks and a > small description of how they interact/nest. > Sure. I'll put together whatever I have understood, in the form of a patch to Documentation/power directory and post it tomorrow, for the benefit of all. > I just remember being very surprised about finding out the hotplug usage > of suspend/hibernate wasn't at all serialized against the regular > hotplug thingies.. (see 144060fee07e9c22e179d00819c83c86fbcbf82c). > > > -- Regards, Srivatsa S. Bhat Linux Technology Center, IBM India Systems and Technology Lab