From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262993AbUB0TMp (ORCPT ); Fri, 27 Feb 2004 14:12:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262935AbUB0TJz (ORCPT ); Fri, 27 Feb 2004 14:09:55 -0500 Received: from [66.35.79.110] ([66.35.79.110]:37766 "EHLO www.hockin.org") by vger.kernel.org with ESMTP id S262934AbUB0TJd (ORCPT ); Fri, 27 Feb 2004 14:09:33 -0500 Date: Fri, 27 Feb 2004 11:09:14 -0800 From: Tim Hockin To: Matt Mackall Cc: "Grover, Andrew" , Helge Hafting , linux-kernel@vger.kernel.org Subject: Re: Why no interrupt priorities? Message-ID: <20040227190914.GA21737@hockin.org> References: <20040227185555.GJ3883@waste.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040227185555.GJ3883@waste.org> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 27, 2004 at 12:55:55PM -0600, Matt Mackall wrote: > Let's imagine you have n sources simultaneously interrupting on a > given descriptor. Check the first, it's happening, acknowledge it, > exit, notice interrupt still asserted, check the first, nope, check > the second, yep, exit, etc. By the time we've made it to the nth ISR, > we've banged on the first one n times, the second n-1 times, etc. In > other words, early chain termination has an O(n^2) worst case. That is a pretty pathological worst case, and n is (almost?) always small. I don't know if it would make a lick of difference, or if it is worth the risk. Someone who has a lot of shared interrupts ought to try it.