From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S946198AbXHMTKs (ORCPT ); Mon, 13 Aug 2007 15:10:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1762180AbXHMTJI (ORCPT ); Mon, 13 Aug 2007 15:09:08 -0400 Received: from gate.crashing.org ([63.228.1.57]:37275 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760098AbXHMTJF (ORCPT ); Mon, 13 Aug 2007 15:09:05 -0400 Subject: Re: [patch 3/3] genirq: mark io_apic level interrupts to avoid resend From: Benjamin Herrenschmidt To: Thomas Gleixner Cc: Jarek Poplawski , Andrew Morton , Linus Torvalds , LKML , Ingo Molnar , Stable Team , Jean-Baptiste Vignaud , "marcin.slusarz" In-Reply-To: <1187006835.12828.112.camel@chaos> References: <20070812152213.551812576@inhelltoy.tec.linutronix.de> <20070812152303.177006193@inhelltoy.tec.linutronix.de> <20070813112821.GA2863@ff.dom.local> <1187006835.12828.112.camel@chaos> Content-Type: text/plain Date: Mon, 13 Aug 2007 13:42:12 -0500 Message-Id: <1187030532.5330.11.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.10.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > handle_fasteoi_irq is special. It is used by ioapic and weird Powerpc > hardware. We marked the ioapic level interrupts IRQ_LEVEL, so we wont > get a resend on them (see kernel/irq/resend.c) s/weird/sane :-) More specifically, it's used by "intelligent" PICs that automatically do the masking of the source (or internally handle priority levels) and only need an "eoi" when the OS is finished processing the latest interrupt. (On those PICs, the ack is generally an implicit part of fetching the next pending interrupt, and the eoi consist of bringing the current processor priority back to what it was before the interrupt occured). I also suspect that any hypervisor using a different method than this one for paravirt irqs is broken :-) Ben.