Date: Mon, 28 Jun 1999 18:56:59 +0800 From: Peter Wemm <peter@netplex.com.au> To: Alan Cox <alc@cs.rice.edu> Cc: Terry Lambert <tlambert@primenet.com>, Bakul Shah <bakul@torrentnet.com>, julian@whistle.com, dillon@apollo.backplane.com, freebsd-smp@freebsd.org Subject: Re: high-efficiency SMP locks - submission for review Message-ID: <19990628105659.8E8F582@overcee.netplex.com.au> In-Reply-To: Your message of "Mon, 28 Jun 1999 00:36:39 EST." <19990628003639.N2738@cs.rice.edu>
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Alan Cox wrote: > On Mon, Jun 28, 1999 at 05:21:05AM +0000, Terry Lambert wrote: > > > > I also have a slight problem with relying on a test-and-set > > instruction any more complicated than that which can be > > implemented with P/V semaphores. Many processors (e.g. MIPS) > > don't have an atomic test and set, and you'd want to avoid > > architecting against them ever working. 8-(. > > > > That is true. They, including MIPS and Alpha, have something > better: Load-locked and store conditional. :-) > > I think this is a non-issue. > > Alan 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 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-smp" in the body of the message
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