Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422942AbXBHLth (ORCPT ); Thu, 8 Feb 2007 06:49:37 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1422946AbXBHLth (ORCPT ); Thu, 8 Feb 2007 06:49:37 -0500 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:38716 "EHLO ebiederm.dsl.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1422942AbXBHLtg (ORCPT ); Thu, 8 Feb 2007 06:49:36 -0500 From: ebiederm@xmission.com (Eric W. Biederman) To: Ingo Molnar Cc: Andrew Morton , linux-kernel@vger.kernel.org, "Lu, Yinghai" , Luigi Genoni , Natalie Protasevich , Andi Kleen Subject: Re: [PATCH 2/2] x86_64 irq: Handle irqs pending in IRR during irq migration. References: <200701221116.13154.luigi.genoni@pirelli.com> <200702021848.55921.luigi.genoni@pirelli.com> <200702021905.39922.luigi.genoni@pirelli.com> <20070206073616.GA15016@elte.hu> <20070206222523.GA11602@elte.hu> Date: Thu, 08 Feb 2007 04:48:50 -0700 In-Reply-To: <20070206222523.GA11602@elte.hu> (Ingo Molnar's message of "Tue, 6 Feb 2007 23:25:23 +0100") Message-ID: User-Agent: Gnus/5.110006 (No Gnus v0.6) Emacs/21.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1796 Lines: 51 Ingo Molnar writes: > * Eric W. Biederman wrote: > >> Ingo would it be reasonable to get a wait queue so I can wait for an >> irq that needs the delayed disable action to actually become masked? > > that might make sense, but what will do the wakeup - incidental IRQ > arriving on the new CPU? Isnt that a bit risky - maybe the device wont > generate IRQs for a really long time. I still need to test this, but I believe I have found a simpler way to avoid irr problems during migration, and I believe the code works equally well with either edge or level triggered interrupts. The idea is this: Instead of trying test for and handle when irr occurs, simply enable local interrupts after disabling and acknowledging the irq so that anything pending will be processed, before we perform the migration operation. I don't think the edge case cares about the mask/ack order but but masking before acking appears important for the level triggered case, so we might as well use that order for both. Does this look like a sane way to handle this? static void ack_apic(unsigned int irq) { struct irq_desc *desc = irq_desc + irq; int do_unmask_irq = 0; if (unlikely((irq_desc[irq].status & IRQ_MOVE_PENDING) && !in_irq()) { do_unmask_irq = 1; desc->chip->mask(irq); } ack_APIC_irq(); if (unlikely(do_unmask_irq)) { /* Don't let pending irqs accumulate */ local_irq_enable(); syncrhonize_irq(irq); move_masked_irq(irq); local_irq_disable(); desc->chip->unmask(irq); } } Eric - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/