From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756699AbYECXir (ORCPT ); Sat, 3 May 2008 19:38:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754573AbYECXik (ORCPT ); Sat, 3 May 2008 19:38:40 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:40075 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754491AbYECXij (ORCPT ); Sat, 3 May 2008 19:38:39 -0400 Date: Sun, 4 May 2008 01:38:25 +0200 From: Ingo Molnar To: David Miller Cc: benh@kernel.crashing.org, a.p.zijlstra@chello.nl, efault@gmx.de, elendil@planet.nl, parag.warudkar@gmail.com, linux-kernel@vger.kernel.org, guichaz@yahoo.fr, andi@firstfloor.org Subject: Re: 'global' rq->clock Message-ID: <20080503233825.GB30600@elte.hu> References: <1209853855.26383.28.camel@pasglop> <20080503223844.GA18344@elte.hu> <20080503.160408.238581868.davem@davemloft.net> <20080503.163600.93588714.davem@davemloft.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080503.163600.93588714.davem@davemloft.net> User-Agent: Mutt/1.5.17 (2007-11-01) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * David Miller wrote: > From: David Miller > Date: Sat, 03 May 2008 16:04:08 -0700 (PDT) > > > From: Ingo Molnar > > Date: Sun, 4 May 2008 00:38:44 +0200 > > > > > the same bug existed on x86 too: that too does a few IPIs without > > > irq_enter/irq_exit. We now removed the softlockup dependency so it > > > should not be required to do an irq_enter()/exit anymore - unless the > > > code that the IPI uses accesses jiffies. (but that would be unusual) > > > > That move doesn't solve the problem, I'm strongly certain > > arch's still need to add the irq_{enter,exit}(). > > > > I'll revert the irq_{enter,exit}() changes on one of my > > sparc64 boxes to validate this later today. > > False alarm, which is good news, thanks Ingo. I can revert the > following it seems: > > commit 2664ef44cf5053d2b7dff01cecac70bc601a5f68 > Author: David S. Miller > Date: Fri Apr 25 03:11:37 2008 -0700 > > [SPARC64]: Wrap SMP IPIs with irq_enter()/irq_exit(). ah, good! It really looks like unnecessary overhead for the "simple IPIs". But ... i'm wondering ... what about softirq processing? Do these IPIs process softirqs on the way out? In that case the non-processed jiffies might be a problem. it's all a bit messy. I wish we could start turning jiffies into a function (which would just read GTOD and estimate jiffies from there), but i fear we are not there yet ... Ingo