From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764902AbXG2Pl2 (ORCPT ); Sun, 29 Jul 2007 11:41:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1761278AbXG2PlU (ORCPT ); Sun, 29 Jul 2007 11:41:20 -0400 Received: from shawidc-mo1.cg.shawcable.net ([24.71.223.10]:64262 "EHLO pd2mo1so.prod.shaw.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760567AbXG2PlT (ORCPT ); Sun, 29 Jul 2007 11:41:19 -0400 Date: Sun, 29 Jul 2007 09:41:04 -0600 From: Robert Hancock Subject: Re: IRQF_DISABLED problem In-reply-to: To: David Miller Cc: arjan@infradead.org, torvalds@linux-foundation.org, matthew@wil.cx, mingo@elte.hu, linux-kernel@vger.kernel.org Message-id: <46ACB510.5060700@shaw.ca> MIME-version: 1.0 Content-type: text/plain; charset=ISO-8859-1; format=flowed Content-transfer-encoding: 7bit References: User-Agent: Thunderbird 2.0.0.5 (Windows/20070716) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org David Miller wrote: > From: Arjan van de Ven > Date: Fri, 27 Jul 2007 13:11:56 -0700 > >> On Thu, 2007-07-26 at 16:17 -0700, Linus Torvalds wrote: >>> On Thu, 26 Jul 2007, Linus Torvalds wrote: >>>> (c) "one IRQF_DISABLED means that everything runs disabled". This is >>>> quite possibly buggy. >>> (Side note: I'm not claiming this (or it's mirror image (d)) is really any >>> better/worse than the current behaviour from a theoretical standpoint, but >>> at least the current behaviour is _tested_, which makes it better in >>> practice. So if we want to change this, I think we want to change it to >>> something that is _obviously_ better). >> my personal preference would actually be to just never enable >> interrupts. It's the fastest solution obviously, the most friendly on >> stack and.. well simplest. Drivers no longer need to play some of the >> games that they do today. And while there is an argument that this may >> introduce a bit of latency... I'm not really convinced. > > If you have a "chirpy" serial controller with only a 1 byte > fifo, even a quite reasonable interrupt handler can cause > receive characters to get lost if you disable interrupts during > the entirety of it's execution. > > It really is needed. > > And it's just plain rude to disable interrupts when it isn't > absolutely necessary. Does anyone really use those serial controllers with no FIFO anymore? They've never been reliable for remotely high speeds.. -- Robert Hancock Saskatoon, SK, Canada To email, remove "nospam" from hancockr@nospamshaw.ca Home Page: http://www.roberthancock.com/