From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753867Ab1JQBtf (ORCPT ); Sun, 16 Oct 2011 21:49:35 -0400 Received: from relay4-d.mail.gandi.net ([217.70.183.196]:52087 "EHLO relay4-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750876Ab1JQBte (ORCPT ); Sun, 16 Oct 2011 21:49:34 -0400 X-Originating-IP: 217.70.178.131 X-Originating-IP: 50.43.15.19 Date: Sun, 16 Oct 2011 18:49:15 -0700 From: Josh Triplett To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, patches@linaro.org, "Paul E. McKenney" Subject: Re: [PATCH tip/core/rcu 36/55] rcu: Prevent early boot set_need_resched() from __rcu_pending() Message-ID: <20111017014915.GE19421@leaf> References: <20110906180015.GA2560@linux.vnet.ibm.com> <1315332049-2604-36-git-send-email-paulmck@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1315332049-2604-36-git-send-email-paulmck@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 06, 2011 at 11:00:30AM -0700, Paul E. McKenney wrote: > From: Paul E. McKenney > > There isn't a whole lot of point in poking the scheduler before there > are other tasks to switch to. This commit therefore adds a check > for rcu_scheduler_fully_active in __rcu_pending() to suppress any > pre-scheduler calls to set_need_resched(). The downside of this approach > is additional runtime overhead in a reasonably hot code path. If you're concerned about the runtime overhead, this does seem like a perfect candidate for jump labels. - Josh Triplett