From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932915Ab3BZTSS (ORCPT ); Tue, 26 Feb 2013 14:18:18 -0500 Received: from e9.ny.us.ibm.com ([32.97.182.139]:40694 "EHLO e9.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932591Ab3BZTSR (ORCPT ); Tue, 26 Feb 2013 14:18:17 -0500 Date: Tue, 26 Feb 2013 11:17:58 -0800 From: "Paul E. McKenney" To: Thomas Gleixner Cc: Frederic Weisbecker , Linus Torvalds , LKML , Ingo Molnar , Peter Zijlstra Subject: Re: [PATCH 2/2] irq: Cleanup context state transitions in irq_exit() Message-ID: <20130226191758.GA28847@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1361496971-16939-3-git-send-email-fweisbec@gmail.com> <20130222150444.GD18149@somewhere.redhat.com> <20130226163911.GA3309@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13022619-7182-0000-0000-00000587E779 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 26, 2013 at 07:55:06PM +0100, Thomas Gleixner wrote: > On Tue, 26 Feb 2013, Paul E. McKenney wrote: > > On Tue, Feb 26, 2013 at 04:14:43PM +0100, Thomas Gleixner wrote: > > > > > > On Tue, 26 Feb 2013, Frederic Weisbecker wrote: > > > > And what do you think about Linus's idea to move tick_nohz_irq_exit() > > > > to do_softirq()? > > > > This sounds feasible and a right place to do this, I hope that won't > > > > uglify do_softirq() though. > > > > I can try something. > > > > > > Yeah, looks doable. the rcu stuff needs to go there as well, right? > > > > If it does, it needs to do so in such a way that rcu_irq_enter() and > > rcu_irq_exit() nest properly. One area of concern is the force_irqthreads > > case, skips calling do_softirq(). Another area of concern is the > > __ARCH_IRQ_EXIT_IRQS_DISABLED case, which calls __do_softirq() rather > > than do_softirq(). > > That's sorted already. We disable interrupts in irq_exit(). > > > Or am I missing some adjustment that is to be made when moving rcu_irq_exit() > > to do_softirq()? > > Yeah, we need an extra parameter or such, so the other callers of > __do_softirq() don't mess with it. > > I also noticed that rcu_irq_enter/exit needs to be symetric and the > NOHZ code will get confused as well if we call it asymetric. Exactly! Thanx, Paul > So that will become even more ugly than the extra check at the end of > irq_exit(). > > Thanks, > > tglx > > >