From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753842AbaHMSYO (ORCPT ); Wed, 13 Aug 2014 14:24:14 -0400 Received: from e36.co.us.ibm.com ([32.97.110.154]:60639 "EHLO e36.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753245AbaHMSYM (ORCPT ); Wed, 13 Aug 2014 14:24:12 -0400 Date: Wed, 13 Aug 2014 11:24:07 -0700 From: "Paul E. McKenney" To: Jacob Pan Cc: Peter Zijlstra , Steven Rostedt , linux-kernel@vger.kernel.org, mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com Subject: Re: [PATCH v5 tip/core/rcu 15/16] rcu: Make RCU-tasks wait for idle tasks Message-ID: <20140813182406.GE4752@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1407797345-28227-15-git-send-email-paulmck@linux.vnet.ibm.com> <20140813081215.GB9918@twins.programming.kicks-ass.net> <20140813124818.GQ4752@linux.vnet.ibm.com> <20140813134025.GN9918@twins.programming.kicks-ass.net> <20140813095132.56d288f2@gandalf.local.home> <20140813140705.GO9918@twins.programming.kicks-ass.net> <20140813101301.08019895@gandalf.local.home> <20140813144332.GW4752@linux.vnet.ibm.com> <20140813163015.GT9918@twins.programming.kicks-ass.net> <20140813094305.225a4e1c@ultegra> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140813094305.225a4e1c@ultegra> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14081318-3532-0000-0000-000003D244FA Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 13, 2014 at 09:43:05AM -0700, Jacob Pan wrote: > On Wed, 13 Aug 2014 18:30:15 +0200 > Peter Zijlstra wrote: > > > On Wed, Aug 13, 2014 at 07:43:32AM -0700, Paul E. McKenney wrote: > > > o drivers/acpi/acpi_pad.c, power_saving_thread(). > > > > > > Looks like a kthread that does idle injection. Currently, > > > RCU sees it as not a quiescent state. Would it kill these guys to > > > put in a comment or two about what this is for??? > > > > > > So adding rcu_idle_enter() and rcu_idle_exit() here might > > > actually fix a bug, though it is not clear how long this > > > thing actually runs. If only for a few milliseconds, no harm done. > > > > > > > > o drivers/thermal/intel_powerclamp.c, clamp_thread(). > > > > > > Looks similar to power_saving_thread(), but for thermal > > > control. Probably short term, shouldn't be a problem either way. > > > > > > > There's patches somewhere that make that go-away > > > > https://lkml.org/lkml/2014/6/4/56 > > > > Jacob was going to look at that. > > yes, it is on my plate, plan to submit for 3.18. the idle period is > only for a few miliseconds, default to 6ms. OK, 6ms shouldn't be a problem. But if you want much longer, you will need to do rcu_idle_enter() and rcu_idle_exit(). Of course, if you are getting rid of this entirely, no need to worry -- though the patch looks like it just uses a different idle loop. Thanx, Paul