From owner-freebsd-arch Wed Jan 2 17:19:47 2002 Delivered-To: freebsd-arch@freebsd.org Received: from srv1.cosmo-project.de (srv1.cosmo-project.de [213.83.6.106]) by hub.freebsd.org (Postfix) with ESMTP id 0B72C37B417; Wed, 2 Jan 2002 17:19:44 -0800 (PST) Received: (from uucp@localhost) by srv1.cosmo-project.de (8.11.6/8.11.6) with UUCP id g031JOJ06834; Thu, 3 Jan 2002 02:19:24 +0100 (CET) (envelope-from ticso@cicely9.cicely.de) Received: from mail.cicely.de (cicely20.cicely.de [10.1.1.22]) by cicely5.cicely.de (8.12.1/8.12.1) with ESMTP id g031Gktx046537; Thu, 3 Jan 2002 02:16:46 +0100 (CET)?g (envelope-from ticso@cicely9.cicely.de) Received: from cicely9.cicely.de (cicely9.cicely.de [10.1.7.11]) by mail.cicely.de (8.11.0/8.11.0) with ESMTP id g031GkW12942; Thu, 3 Jan 2002 02:16:46 +0100 (CET) Received: (from ticso@localhost) by cicely9.cicely.de (8.11.6/8.11.6) id g031Gj862401; Thu, 3 Jan 2002 02:16:45 +0100 (CET) (envelope-from ticso) Date: Thu, 3 Jan 2002 02:16:45 +0100 From: Bernd Walter To: Peter Jeremy Cc: Michal Mertl , Matthew Dillon , Bruce Evans , Mike Smith , Bernd Walter , arch@FreeBSD.ORG Subject: Re: When to use atomic_ functions? (was: 64 bit counters) Message-ID: <20020103011645.GE53199@cicely9.cicely.de> References: <200201012349.g01NnKA40071@apollo.backplane.com> <20020103095701.B561@gsmx07.alcatel.com.au> <20020103002521.GB53199@cicely9.cicely.de> <20020103113919.E561@gsmx07.alcatel.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20020103113919.E561@gsmx07.alcatel.com.au> User-Agent: Mutt/1.3.24i X-Operating-System: FreeBSD cicely9.cicely.de 5.0-CURRENT alpha Sender: owner-freebsd-arch@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Thu, Jan 03, 2002 at 11:39:20AM +1100, Peter Jeremy wrote: > On 2002-Jan-03 01:25:22 +0100, Bernd Walter wrote: > >My Alpha Architecture Handbook says that the barrier is unneeded. > >I have no clue why they are there. > > You're right. Version 2, section 5.5 shows that they aren't needed > when a single datum is being atomically updated (as needed here). > They're only needed where the atomic operation is seizing a lock so > that a larger structure can be atomically updated. I will do this change localy a send a patch to -alpha. Maybe we can also remove the barriers for rel/acq in the non SMP case, but I could also be wrong if drivers depend on them. -- B.Walter COSMO-Project http://www.cosmo-project.de ticso@cicely.de Usergroup info@cosmo-project.de To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message