Date: Mon, 04 Jul 2005 12:12:53 +0200 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: Peter Grehan <grehan@freebsd.org> Cc: cvs-src@freebsd.org, src-committers@freebsd.org, Robert Watson <rwatson@freebsd.org>, cvs-all@freebsd.org, Andrew Thompson <thompsa@freebsd.org> Subject: Re: cvs commit: src/sys/amd64/include _types.h src/sys/i386/include _types.h src/sys/net if_bridge.c src/sys/netinet ip_var.h src/sys/netinet6 ip6_var.h Message-ID: <29301.1120471973@phk.freebsd.dk> In-Reply-To: Your message of "Mon, 04 Jul 2005 20:06:33 %2B1000." <42C90A29.2030706@freebsd.org>
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In message <42C90A29.2030706@freebsd.org>, Peter Grehan writes: >>> FYI, any modern ppc implementation doesn't require strict alignment >>> for integer load/stores though there's a performance penalty for >>> having to split the access into smaller ones. >> >> While it's not immediately relevant to the IP code, generally speaking, >> is it the case that non-aligned integer reads can be non-atomic with >> respect to other CPUs due to the multiple access implementation? > > I'd say certainly ! In fact, are there any architectures that could >guarantee atomicity in this case ? Yes, the alphas "load/store conditional" could, provided that the field is entirely inside a cache-line. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.
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