From owner-freebsd-arch@FreeBSD.ORG Wed Mar 24 07:41:05 2004 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 0A6DC16A4CF for ; Wed, 24 Mar 2004 07:41:05 -0800 (PST) Received: from mail2.speakeasy.net (mail2.speakeasy.net [216.254.0.202]) by mx1.FreeBSD.org (Postfix) with ESMTP id DC3BE43D41 for ; Wed, 24 Mar 2004 07:41:04 -0800 (PST) (envelope-from jhb@FreeBSD.org) Received: (qmail 9904 invoked from network); 24 Mar 2004 15:41:04 -0000 Received: from dsl027-160-063.atl1.dsl.speakeasy.net (HELO server.baldwin.cx) ([216.27.160.63]) (envelope-sender ) encrypted SMTP for ; 24 Mar 2004 15:41:04 -0000 Received: from 10.50.40.205 (gw1.twc.weather.com [216.133.140.1]) by server.baldwin.cx (8.12.10/8.12.10) with ESMTP id i2OFe6DJ004603; Wed, 24 Mar 2004 10:40:52 -0500 (EST) (envelope-from jhb@FreeBSD.org) From: John Baldwin To: des@des.no (Dag-Erling =?utf-8?q?Sm=C3=B8rgrav?=) Date: Tue, 23 Mar 2004 17:24:45 -0500 User-Agent: KMail/1.6 References: <200403160519.i2G5J0V6023193@urban> In-Reply-To: MIME-Version: 1.0 Content-Disposition: inline Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <200403231724.45923.jhb@FreeBSD.org> X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on server.baldwin.cx cc: arch@FreeBSD.ORG cc: David Schultz cc: Seigo Tanimura Subject: Re: Is MTX_CONTESTED evil? X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 24 Mar 2004 15:41:05 -0000 On Tuesday 23 March 2004 03:06 pm, Dag-Erling Sm=C3=B8rgrav wrote: > des@des.no (Dag-Erling Sm=C3=B8rgrav) writes: > > John Baldwin writes: > > > Adaptive mutexes work just fine, but they aren't on by default. > > > > No, they don't "work just fine", unless of course they are *supposed* > > to cause frequent panics. > > s/panic/freeze/ They worked just fine on sparc64, alpha, and i386 when they were developed = and=20 nothing has changed since then. However, since they increase the chances o= f=20 "near concurrency" on multiple CPUs (i.e. one CPU grabbing a lock right aft= er=20 another released it) they expose races and thus bugs in code that uses=20 mutexes improperly. The fault is not in adaptive mutexes, but in the other= =20 broken code, just as compile failures aren't the result of the tinderbox=20 itself being broken. :-) =2D-=20 John Baldwin <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" =3D http://www.FreeBSD.org