From owner-freebsd-hackers@FreeBSD.ORG Mon Feb 25 13:37:05 2008 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id E61F216A400 for ; Mon, 25 Feb 2008 13:37:05 +0000 (UTC) (envelope-from robert.woolley@rwoolley.com) Received: from turtle-out.mxes.net (turtle-out.mxes.net [216.86.168.191]) by mx1.freebsd.org (Postfix) with ESMTP id BFC1913C45D for ; Mon, 25 Feb 2008 13:37:05 +0000 (UTC) (envelope-from robert.woolley@rwoolley.com) Received: from mxout-03.mxes.net (mxout-03.mxes.net [216.86.168.178]) by turtle-in.mxes.net (Postfix) with ESMTP id BCF18163F78 for ; Mon, 25 Feb 2008 08:15:52 -0500 (EST) Received: from gumby.homeunix.com. (unknown [87.81.140.128]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.mxes.net (Postfix) with ESMTP id 114F323E4AD for ; Mon, 25 Feb 2008 08:15:49 -0500 (EST) Date: Mon, 25 Feb 2008 13:15:46 +0000 From: Robert Woolley To: freebsd-hackers@freebsd.org Message-ID: <20080225131546.0d9d2f22@gumby.homeunix.com.> In-Reply-To: <200802251039.59767.wundram@beenic.net> References: <200802221558.42443.sharadc@in.niksun.com> <200802221437.48293.wundram@beenic.net> <200802251440.56435.sharadc@in.niksun.com> <200802251039.59767.wundram@beenic.net> X-Mailer: Claws Mail 3.3.0 (GTK+ 2.12.8; i386-portbld-freebsd7.0) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Mailman-Approved-At: Mon, 25 Feb 2008 14:25:58 +0000 Subject: Re: usleep X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 25 Feb 2008 13:37:06 -0000 On Mon, 25 Feb 2008 10:39:59 +0100 "Heiko Wundram (Beenic)" wrote: > Am Montag, 25. Februar 2008 10:10:56 schrieb Sharad Chandra: > > So does it mean, freebsd has limitation. sleeping will only work > > for its value more than 1 milli sec because % of +- error value is > > comparitivly low? I am curious to know, is there any method which > > sleeps for few microseconds. Some one please give me link where to > > look for "select". > > No, this does not mean that FreeBSD has a limitation, but rather that > FreeBSD is not a real-time operating system. You'll see the similar > behaviour on pretty much any other operating system that is _not_ a > RTOS It's actually not a distinguishing feature of RTOSs. I haven't worked on them for a few years, but when I did, both pSOS and VxWorks had this limitation. The important thing is that RTOSs handle interrupts well. In traditional real-time software, sleeping is something that happens in non-critical background tasks.