Date: Tue, 29 Jun 1999 01:18:23 +0800 From: Peter Wemm <peter@netplex.com.au> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: Alan Cox <alc@cs.rice.edu>, Terry Lambert <tlambert@primenet.com>, Bakul Shah <bakul@torrentnet.com>, julian@whistle.com, freebsd-smp@freebsd.org Subject: Re: high-efficiency SMP locks - submission for review Message-ID: <19990628171823.3445882@overcee.netplex.com.au> In-Reply-To: Your message of "Mon, 28 Jun 1999 09:11:47 MST." <199906281611.JAA22481@apollo.backplane.com>
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Matthew Dillon wrote: > :Actually, I have a bigger issue with it.. cmpxchgl etc doesn't exist on > :all x86 cpus. To make a kernel that boots on the current cpus (including > :the 486) we either have to conditionalize the inlines or use the > :universally available (and implicitly locked) xchg instruction - but that's > :a test-and-set style operation rather than atomic_cmpex. > : > :Cheers, > :-Peter > > My "Intel486 Processor Family" book - note the 486, lists the cmpxchgl > instruction. Of course, I've never actually tried it on a 486. I dunno > whether the 386 implements it, though. Ahh, right, silly me. I was thinking of the 8-byte version which is signified by the CX8 bit in cpuid. The 386, I doubt has it. There have been a couple of suggestions for ending the support for the 386 as it will simplify some ugly code for emulating kernel-mode write faults etc, but it's never happened. Apparently the 386 is common in some areas still. Cheers, -Peter To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the message
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