From owner-freebsd-current@FreeBSD.ORG Mon Feb 20 18:58:55 2006 Return-Path: X-Original-To: freebsd-current@freebsd.org Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 76C1816A420; Mon, 20 Feb 2006 18:58:55 +0000 (GMT) (envelope-from jhb@freebsd.org) Received: from server.baldwin.cx (66-23-211-162.clients.speedfactory.net [66.23.211.162]) by mx1.FreeBSD.org (Postfix) with ESMTP id E104743D46; Mon, 20 Feb 2006 18:58:54 +0000 (GMT) (envelope-from jhb@freebsd.org) Received: from localhost (john@localhost [127.0.0.1]) by server.baldwin.cx (8.13.4/8.13.4) with ESMTP id k1KIwoVR022835; Mon, 20 Feb 2006 13:58:52 -0500 (EST) (envelope-from jhb@freebsd.org) From: John Baldwin To: Andrew Thompson Date: Mon, 20 Feb 2006 13:43:48 -0500 User-Agent: KMail/1.9.1 References: <20060215211534.GA78376@heff.fud.org.nz> <200602171342.13451.jhb@freebsd.org> <20060219041012.GB78376@heff.fud.org.nz> In-Reply-To: <20060219041012.GB78376@heff.fud.org.nz> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200602201343.49927.jhb@freebsd.org> X-Virus-Scanned: ClamAV 0.87.1/1293/Sun Feb 19 11:40:25 2006 on server.baldwin.cx X-Virus-Status: Clean X-Spam-Status: No, score=-1.4 required=4.2 tests=ALL_TRUSTED,AWL autolearn=ham version=3.1.0 X-Spam-Checker-Version: SpamAssassin 3.1.0 (2005-09-13) on server.baldwin.cx Cc: freebsd-current@freebsd.org Subject: Re: rwlock patch for bridge X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 20 Feb 2006 18:58:55 -0000 On Saturday 18 February 2006 23:10, Andrew Thompson wrote: > On Fri, Feb 17, 2006 at 01:42:11PM -0500, John Baldwin wrote: > > On Wednesday 15 February 2006 16:15, Andrew Thompson wrote: > > > Here is a patch that changes if_bridge to use rwlock(9) rather than the > > > handrolled ref counting. Can I please get it reviewed to ensure I have > > > the changes correct. I pondered if the order of unlocking the softc > > > mutex and grabbing the rlock mattered but decided it didn't. > > > > Have you thought about replacing both the mutex and ref-count with the > > single rwlock? (Perhaps that is infeasible, but it would be somewhat > > pointless to just lock one lock so you can turn around and lock the > > next.) > > The bridge code makes use of callout_init_mtx(), can a rwlock be passed > instead of a mutex? No. You could use callout_init() and mark it MPSAFE and handle the teardown race yourself perhaps. I'd be interested in benchmarks, btw, of this patch as I'd imagine it is actually a pessimization because you are trading simple arith operations for atomic operations to mess with the rw lock. -- John Baldwin <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" = http://www.FreeBSD.org