From owner-svn-src-head@FreeBSD.ORG Wed Nov 4 12:49:43 2009 Return-Path: Delivered-To: svn-src-head@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 2C178106566C; Wed, 4 Nov 2009 12:49:43 +0000 (UTC) (envelope-from asmrookie@gmail.com) Received: from mail-bw0-f213.google.com (mail-bw0-f213.google.com [209.85.218.213]) by mx1.freebsd.org (Postfix) with ESMTP id 55FBC8FC13; Wed, 4 Nov 2009 12:49:41 +0000 (UTC) Received: by bwz5 with SMTP id 5so9042286bwz.3 for ; Wed, 04 Nov 2009 04:49:41 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:sender:received:in-reply-to :references:date:x-google-sender-auth:message-id:subject:from:to:cc :content-type; bh=XpNh1akFifabyW1zu5RBTwZW2CnpDJUbYHykLCw7ihs=; b=OsTNwiraP03cwRpbOIrgP2IbPQZLCEA5ArhXUdkYLXPTR1kvEZURIpeMsuXx679h55 Ls8bHUx/g6Qqwe2mCyfv3tXA+rje+5ooKSnfWDeL4xXi5BK7c7on0HRuMJMR9V8EJ/zd naNPSFYPA4De8DdLwgDTQiI0qTBwEEbgWP4PM= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type; b=BeaoHFw9/VQzH3FaMdOQar58yoXJGGARJrKyirHxxCTitx07/JnjH6O5zexE+E1+ZE 5+nlRCnzi2Olzgnf2GFLcjGeTFxQyeEKaL4WZQweA4LOX3EKzpl9Mc7LzHkWvydin0/b a5u2YR6pd02Qa1eXrvcijS7fYanJCHdUC+qBs= MIME-Version: 1.0 Sender: asmrookie@gmail.com Received: by 10.223.14.140 with SMTP id g12mr201744faa.50.1257338981090; Wed, 04 Nov 2009 04:49:41 -0800 (PST) In-Reply-To: <20091104055811.GY1293@hoeg.nl> References: <200911040132.nA41WxtQ012750@svn.freebsd.org> <20091104055811.GY1293@hoeg.nl> Date: Wed, 4 Nov 2009 13:49:41 +0100 X-Google-Sender-Auth: 531ed258d7574ae1 Message-ID: <3bbf2fe10911040449j5938ca7eqca5829ceced66f48@mail.gmail.com> From: Attilio Rao To: Ed Schouten Content-Type: text/plain; charset=UTF-8 Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r198868 - in head/sys: amd64/amd64 i386/i386 X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 04 Nov 2009 12:49:43 -0000 2009/11/4 Ed Schouten : > Hi Attilio, > > * Attilio Rao wrote: >> Opteron rev E family of processor expose a bug where, in very rare >> ocassions, memory barriers semantic is not honoured by the hardware >> itself. As a result, some random breakage can happen in uninvestigable >> ways (for further explanation see at the content of the commit itself). > > Ooh. Sounds like an interesting bug. > > The bug doesn't manifest itself on UP, right? If so, maybe we should add > some very short instructions to the warning on how to disable SMP. Due to the semantic of the bug, I think that it can manifest itself on UP and a memory barrier failing on UP means that PREEMPTION can blow up. Considering this I wouldn't suggest anything different between the UP vs SMP case. Attilio -- Peace can only be achieved by understanding - A. Einstein