From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Tue, 02 Oct 2007 21:27:39 +0100 (BST) Received: from il.qumranet.com ([82.166.9.18]:9345 "EHLO il.qumranet.com") by ftp.linux-mips.org with ESMTP id S20022629AbXJBU1b (ORCPT ); Tue, 2 Oct 2007 21:27:31 +0100 Received: from [10.64.7.18] (unknown [10.64.7.18]) by il.qumranet.com (Postfix) with ESMTP id AF838250D39; Tue, 2 Oct 2007 22:27:41 +0200 (IST) Message-ID: <4702A99B.7020008@qumranet.com> Date: Tue, 02 Oct 2007 22:27:07 +0200 From: Avi Kivity User-Agent: Thunderbird 2.0.0.5 (X11/20070727) MIME-Version: 1.0 To: qemu-devel@nongnu.org CC: linux-mips@linux-mips.org Subject: Re: [Qemu-devel] QEMU/MIPS & dyntick kernel References: <20071002200644.GA19140@hall.aurel32.net> In-Reply-To: <20071002200644.GA19140@hall.aurel32.net> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 16803 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: avi@qumranet.com Precedence: bulk X-list: linux-mips Aurelien Jarno wrote: > Hi, > > As announced by Ralf Baechle, dyntick is now available on MIPS. I gave a > try on QEMU/MIPS, and unfortunately it doesn't work correctly. > > In some cases the kernel schedules an event very near in the future, > which means the timer is scheduled a few cycles only from its current > value. Unfortunately under QEMU, the timer runs too fast compared to the > speed at which instructions are execution. Sounds like a kernel bug. Can't there conceivably exist real hardware (or a real timeout) that exhibits the same timing? Especially today with variable clock frequencies, I don't see how the kernel can rely on exact timing. -- Any sufficiently difficult bug is indistinguishable from a feature.