Date: Thu, 3 Jan 2002 02:16:45 +0100 From: Bernd Walter <ticso@cicely9.cicely.de> To: Peter Jeremy <peter.jeremy@alcatel.com.au> Cc: Michal Mertl <mime@traveller.cz>, Matthew Dillon <dillon@apollo.backplane.com>, Bruce Evans <bde@zeta.org.au>, Mike Smith <msmith@FreeBSD.ORG>, Bernd Walter <ticso@cicely8.cicely.de>, arch@FreeBSD.ORG Subject: Re: When to use atomic_ functions? (was: 64 bit counters) Message-ID: <20020103011645.GE53199@cicely9.cicely.de> In-Reply-To: <20020103113919.E561@gsmx07.alcatel.com.au> References: <200201012349.g01NnKA40071@apollo.backplane.com> <Pine.BSF.4.41.0201021003580.18429-100000@prg.traveller.cz> <20020103095701.B561@gsmx07.alcatel.com.au> <20020103002521.GB53199@cicely9.cicely.de> <20020103113919.E561@gsmx07.alcatel.com.au>
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On Thu, Jan 03, 2002 at 11:39:20AM +1100, Peter Jeremy wrote: > On 2002-Jan-03 01:25:22 +0100, Bernd Walter <ticso@cicely9.cicely.de> 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
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