From owner-cvs-src@FreeBSD.ORG Fri Aug 8 17:08:17 2008 Return-Path: Delivered-To: cvs-src@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 8F9BE106567D; Fri, 8 Aug 2008 17:08:17 +0000 (UTC) (envelope-from alc@cs.rice.edu) Received: from mail.cs.rice.edu (mail.cs.rice.edu [128.42.1.31]) by mx1.freebsd.org (Postfix) with ESMTP id 5DA558FC19; Fri, 8 Aug 2008 17:08:17 +0000 (UTC) (envelope-from alc@cs.rice.edu) Received: from mail.cs.rice.edu (localhost.localdomain [127.0.0.1]) by mail.cs.rice.edu (Postfix) with ESMTP id DD0FE2C2B02; Fri, 8 Aug 2008 12:08:16 -0500 (CDT) X-Virus-Scanned: by amavis-2.4.0 at mail.cs.rice.edu Received: from mail.cs.rice.edu ([127.0.0.1]) by mail.cs.rice.edu (mail.cs.rice.edu [127.0.0.1]) (amavisd-new, port 10024) with LMTP id NIM8-2OQKFIV; Fri, 8 Aug 2008 12:08:16 -0500 (CDT) Received: from [216.63.78.18] (adsl-216-63-78-18.dsl.hstntx.swbell.net [216.63.78.18]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.cs.rice.edu (Postfix) with ESMTP id D8F7E2C2A81; Fri, 8 Aug 2008 12:08:15 -0500 (CDT) Message-ID: <489C7D7F.4090806@cs.rice.edu> Date: Fri, 08 Aug 2008 12:08:15 -0500 From: Alan Cox User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.7.13) Gecko/20080722 X-Accept-Language: en-us, en MIME-Version: 1.0 To: John Baldwin References: <200808081343.m78DhwYE068477@repoman.freebsd.org> <200808081226.32089.jhb@freebsd.org> In-Reply-To: <200808081226.32089.jhb@freebsd.org> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Cc: cvs-src@freebsd.org, src-committers@freebsd.org, Ed Schouten , cvs-all@freebsd.org Subject: Re: cvs commit: src/sys/dev/io iodev.c X-BeenThere: cvs-src@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: CVS commit messages for the src tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 08 Aug 2008 17:08:17 -0000 John Baldwin wrote: > >Also, I don't see why memrw() is not MPSAFE actually (on amd64 and i386 at >least). Stephan (ups@) even has a comment to that effect. The MTRR stuff >backing memioctl() on x86 might need locking, but I think that is all mem(4) >is missing. > > > There is nothing there that requires Giant specifically. However, the use of some lock in memrw() does have an arguably useful but small effect: overlapping operations will be serialized. So, if you're ever trying to debug something involving memrw(), you won't be staring at essentially random state. Alan