Date: Thu, 3 Jan 2002 10:54:34 +0100 From: Bernd Walter <ticso@cicely9.cicely.de> To: Terry Lambert <tlambert2@mindspring.com> Cc: Matthew Dillon <dillon@apollo.backplane.com>, John Baldwin <jhb@FreeBSD.ORG>, arch@FreeBSD.ORG, Bernd Walter <ticso@cicely8.cicely.de>, Mike Smith <msmith@FreeBSD.ORG>, Bruce Evans <bde@zeta.org.au>, Michal Mertl <mime@traveller.cz>, Peter Jeremy <peter.jeremy@alcatel.com.au> Subject: Re: When to use atomic_ functions? (was: 64 bit counters) Message-ID: <20020103095433.GI53199@cicely9.cicely.de> In-Reply-To: <3C33D580.50B5BCAA@mindspring.com> References: <XFMail.020102152920.jhb@FreeBSD.org> <200201030002.g0302Eo60575@apollo.backplane.com> <20020103003214.GC53199@cicely9.cicely.de> <3C33D580.50B5BCAA@mindspring.com>
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On Wed, Jan 02, 2002 at 07:52:32PM -0800, Terry Lambert wrote: > Bernd Walter wrote: > > You need to hold the mutex while writing and reading. > > If you hold the mutex only while writing another CPU might still use > > old cached values. > > > Unless there are two sounts that MUST remain synchornized for > correct operation, you don't *care* if someone gets the stale > value. > > Ask yourself: what's the worst case failure scenario that would > result? If I ask a value I may get a recent value x. If I ask with another CPU later I may get an older value than x. Having slightly out of date statistisks isn't a problem, but statistiks getting backwards definately are. -- 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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