From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934201AbXGRQ3g (ORCPT ); Wed, 18 Jul 2007 12:29:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932777AbXGRQ3Z (ORCPT ); Wed, 18 Jul 2007 12:29:25 -0400 Received: from smtp102.mail.mud.yahoo.com ([209.191.85.212]:30070 "HELO smtp102.mail.mud.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S933359AbXGRQ3Y (ORCPT ); Wed, 18 Jul 2007 12:29:24 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:X-YMail-OSG:Message-ID:Date:From:User-Agent:X-Accept-Language:MIME-Version:To:CC:Subject:References:In-Reply-To:Content-Type:Content-Transfer-Encoding; b=EztCPYgP4Ry1y1A5JqVG9FR4knyBSOoODnbYRoBfI51zmNSb0pMnS660PJmtTs3FwWehngKXnYYU9R4EIp5xJ+rrNrrpAXRFnGVEJSHmvFlXOKYunyzOEqQaoXjYGmNwEzakicyyRGeKkZeyvqc1pSv/sgYY73X2K0/aIALV4O4= ; X-YMail-OSG: 7hW2eMgVM1lHhQ7PEwyJvhC2cb6ZzPtf7inV.QnPBbk3eF5vn_EcyqapQF1CyJyNP3yQFGWvEw-- Message-ID: <469C3FE8.30505@yahoo.com.au> Date: Tue, 17 Jul 2007 14:04:56 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20051007 Debian/1.7.12-1 X-Accept-Language: en MIME-Version: 1.0 To: Nish Aravamudan CC: Ray Lee , Roman Zippel , Jonathan Corbet , linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar Subject: Re: [PATCH/RFC] msleep() with hrtimers References: <21003.1184596954@lwn.net> <2c0942db0707160857s25cbce19j7f057b14e74651e8@mail.gmail.com> <29495f1d0707160908x32704c7o41ab7857ceac1558@mail.gmail.com> In-Reply-To: <29495f1d0707160908x32704c7o41ab7857ceac1558@mail.gmail.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Nish Aravamudan wrote: > Well, before these changes, the only guarantee msleep() could make, > just like the only guarantee schedule_timeout() could make, was that > it would not return early. The 1-jiffy sleep was always tough to deal > with, because of rounding and such. And it's simply exacerbated with > HZ=100. It's not technically 20 times longer in all cases, it's 2 > jiffies longer, which depends on HZ, so varies from 2 msecs longer to > 20 msecs longer. I don't think you should rely on anything else actually, because Linux is not an RT OS. If your driver needs a specific sequence in a given amount of time, you have to do something like disable interrupts and use delays. -- SUSE Labs, Novell Inc.