From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [PATCH 3/7] idle, thermal, acpi: Remove home grown idle implementations Date: Fri, 22 Nov 2013 09:17:27 -0800 Message-ID: <20131122171727.GT4138@linux.vnet.ibm.com> References: <20131120165406.14fa0f09@ultegra> <20131121082151.GU10022@twins.programming.kicks-ass.net> <20131121160716.GT4138@linux.vnet.ibm.com> <528E32EF.2050300@linux.intel.com> <20131121191916.GZ4138@linux.vnet.ibm.com> <528E62D0.3010003@linux.intel.com> <20131121200717.GB4138@linux.vnet.ibm.com> <20131121161005.34150ab2@ultegra> <20131122042036.GL4138@linux.vnet.ibm.com> <20131122113300.GM10022@twins.programming.kicks-ass.net> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from e39.co.us.ibm.com ([32.97.110.160]:59496 "EHLO e39.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755795Ab3KVRRe (ORCPT ); Fri, 22 Nov 2013 12:17:34 -0500 Received: from /spool/local by e39.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 22 Nov 2013 10:17:34 -0700 Content-Disposition: inline In-Reply-To: <20131122113300.GM10022@twins.programming.kicks-ass.net> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Peter Zijlstra Cc: Jacob Pan , Arjan van de Ven , lenb@kernel.org, rjw@rjwysocki.net, Eliezer Tamir , Chris Leech , David Miller , rui.zhang@intel.com, Mike Galbraith , Ingo Molnar , hpa@zytor.com, Thomas Gleixner , linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, "Rafael J. Wysocki" On Fri, Nov 22, 2013 at 12:33:00PM +0100, Peter Zijlstra wrote: > On Thu, Nov 21, 2013 at 08:20:36PM -0800, Paul E. McKenney wrote: > > The 6ms to 25ms range should be just fine as far as normal RCU grace > > periods are concerned. However, it does mean that expedited grace > > periods could be delayed: They normally take a few tens of microseconds, > > but if they were unlucky enough to show up during an idle injection, > > they would be magnified by two to three orders of magnitude, which is > > not pretty. > > > > Hence my suggestion of hooking into RCU on idle-injection start and end > > so that RCU considers that time period to be idle. Just like it does > > for user-mode execution on NO_HZ_FULL kernels, so I still don't see this > > approach to be a problem. I must confess that I still don't understand > > what Arjan doesn't like about it. > > Using these patches it would indeed use the RCU idle machinery as per > the normal idle path. OK, sorry for my confusion! > If you can I can add more WARN_ON()s in play_idle() to ensure we're not > called while holding any RCU locks. An rcu_sleep_check() or something similar, please! Thanx, Paul