From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932180Ab1JXMI1 (ORCPT ); Mon, 24 Oct 2011 08:08:27 -0400 Received: from e4.ny.us.ibm.com ([32.97.182.144]:56248 "EHLO e4.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932100Ab1JXMIZ (ORCPT ); Mon, 24 Oct 2011 08:08:25 -0400 Date: Mon, 24 Oct 2011 05:07:18 -0700 From: "Paul E. McKenney" To: Josh Triplett 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: <20111024120718.GD2273@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20110906180015.GA2560@linux.vnet.ibm.com> <1315332049-2604-36-git-send-email-paulmck@linux.vnet.ibm.com> <20111017014915.GE19421@leaf> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20111017014915.GE19421@leaf> User-Agent: Mutt/1.5.20 (2009-06-14) x-cbid: 11102412-3534-0000-0000-000000DB4610 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Oct 16, 2011 at 06:49:15PM -0700, Josh Triplett wrote: > 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. I have added this to my todo list, but would welcome a patch. Thanx, Paul