From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758203AbXKPHRY (ORCPT ); Fri, 16 Nov 2007 02:17:24 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751765AbXKPHRQ (ORCPT ); Fri, 16 Nov 2007 02:17:16 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:39614 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751544AbXKPHRP (ORCPT ); Fri, 16 Nov 2007 02:17:15 -0500 Date: Fri, 16 Nov 2007 08:17:08 +0100 From: Ingo Molnar To: Andrew Morton Cc: Arjan van de Ven , Linux Kernel Mailing List Subject: Re: x86: disable preemption in delay_tsc() Message-ID: <20071116071708.GA2103@elte.hu> References: <200711150400.lAF40lIr020160@hera.kernel.org> <20071115194116.12c7a0f6@laptopd505.fenrus.org> <20071115195234.2dc8406d.akpm@linux-foundation.org> <20071116061332.GF16273@elte.hu> <20071115230859.d9ccea20.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20071115230859.d9ccea20.akpm@linux-foundation.org> 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=3.1.7-deb -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Andrew Morton wrote: > It sounds like it would work OK. What is the setup cost for a usleep? > I'd have thought that code which does something like > > while (i++ < 1000) { > foo(); > udelay(1); > } > > would take qiute a bit longer with such a change? full roundtrip cost ought to be below 10 usecs, depending on the system. There's no problem doing a non-preemptible udelay up to 10 usecs and we could use usleep above that. Ingo