From owner-freebsd-usb@FreeBSD.ORG Sun Aug 24 06:00:13 2008 Return-Path: Delivered-To: freebsd-usb@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 233781065684 for ; Sun, 24 Aug 2008 06:00:13 +0000 (UTC) (envelope-from phk@critter.freebsd.dk) Received: from phk.freebsd.dk (phk.freebsd.dk [130.225.244.222]) by mx1.freebsd.org (Postfix) with ESMTP id D7D628FC17 for ; Sun, 24 Aug 2008 06:00:12 +0000 (UTC) (envelope-from phk@critter.freebsd.dk) Received: from critter.freebsd.dk (unknown [192.168.61.3]) by phk.freebsd.dk (Postfix) with ESMTP id 66B79170E5; Sun, 24 Aug 2008 06:00:11 +0000 (UTC) Received: from critter.freebsd.dk (localhost [127.0.0.1]) by critter.freebsd.dk (8.14.2/8.14.2) with ESMTP id m7O60ADf013746; Sun, 24 Aug 2008 06:00:11 GMT (envelope-from phk@critter.freebsd.dk) To: "M. Warner Losh" From: "Poul-Henning Kamp" In-Reply-To: Your message of "Sat, 23 Aug 2008 22:39:51 CST." <20080823.223951.-962047221.imp@bsdimp.com> Date: Sun, 24 Aug 2008 06:00:10 +0000 Message-ID: <13745.1219557610@critter.freebsd.dk> Sender: phk@critter.freebsd.dk Cc: freebsd-usb@freebsd.org Subject: Re: usb4bsd patch review X-BeenThere: freebsd-usb@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: FreeBSD support for USB List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 24 Aug 2008 06:00:13 -0000 In message <20080823.223951.-962047221.imp@bsdimp.com>, "M. Warner Losh" writes : >In message: <10826.1219511738@critter.freebsd.dk> > "Poul-Henning Kamp" writes: >: In message <20080823.100155.1310242209.imp@bsdimp.com>, "M. Warner Losh" writes >: : >: >: >While this may be a good idea, I'm hesitant about races that it may >: >introduce. This is the classic point of attack: do something between >: >steps of a formerly atomic operation that was made non-atomic. I >: >can't think of anything off the top of my head, but I'm still >: >concerned. >: >: We have ways of closing the race if need be, but they're all slightly >: kludgy, but I am not overly concerned about those races as long as >: the default is to not give access. > >I guess I'm worried about a device that comes and goes and comes back >and there being some difference between the two that causes us to >bogusly do something to the new device that was appropriate for the >old one, but not the new one... That scenario is always present as far as I can tell... -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.