From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751854AbaHIQQ0 (ORCPT ); Sat, 9 Aug 2014 12:16:26 -0400 Received: from e37.co.us.ibm.com ([32.97.110.158]:51834 "EHLO e37.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751138AbaHIQQY (ORCPT ); Sat, 9 Aug 2014 12:16:24 -0400 Date: Sat, 9 Aug 2014 09:05:10 -0700 From: "Paul E. McKenney" To: Steven Rostedt Cc: Peter Zijlstra , 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 v3 tip/core/rcu 1/9] rcu: Add call_rcu_tasks() Message-ID: <20140809160510.GK5821@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20140731215445.GA21933@linux.vnet.ibm.com> <1406843709-23396-1-git-send-email-paulmck@linux.vnet.ibm.com> <20140808191326.GE3935@laptop> <20140808205826.GG5821@linux.vnet.ibm.com> <20140809061514.GK9918@twins.programming.kicks-ass.net> <20140809084439.05778e33@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140809084439.05778e33@gandalf.local.home> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14080916-7164-0000-0000-000003B355E2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Aug 09, 2014 at 08:44:39AM -0400, Steven Rostedt wrote: > On Sat, 9 Aug 2014 08:15:14 +0200 > Peter Zijlstra wrote: > > > > As for idle tasks, I'm not sure about those, I think that we should say > > NO to anything that would require waking idle CPUs, push the pain to > > ftrace/kprobes, we should _not_ be waking idle cpus. > > I agree, but I haven't had a chance to review the patch set (will > probably do that on Monday, just got back from vacation last week and > was inundated by other things). Let me get v5 out first. I expect to have it out by end of Monday. > Does the idle waking happen only when > there's something queued in the call_rcu_tasks()? It should definitely > not be waking all the time. That's just wrong. > > But if it only wakes when something is queued, it wouldn't be burdening > anything, unless it is needed. Indeed, idle waking only happens when there is an RCU-tasks grace period in progress. No RCU-tasks grace period, no RCU-tasks idle waking. Thanx, Paul