Date: Sun, 17 Feb 2002 15:54:06 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Michael Smith <msmith@FreeBSD.ORG> Cc: Poul-Henning Kamp <phk@critter.freebsd.dk>, Bruce Evans <bde@zeta.org.au>, freebsd-current@FreeBSD.ORG Subject: Re: ACPI patch (was Re: 'microuptime() went backwards ...' using ACPI...) Message-ID: <200202172354.g1HNs6407707@apollo.backplane.com> References: <200202172349.g1HNnWA01995@mass.dis.org>
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:I have some reservations about this, because I'm not sure that 10
:successive reads will catch the ripple-counter problem that the old PIIX4s
:have.
Just goes to show that I need to document my code :-)
Those reads are not detecting the ripple-counter problem, they are
figuring out the mask required to guarentee that two successive reads
will return the same counter value so the counter read in the later
code doesn't end up in an infinite loop.
i.e. on a slow cpu the mask might have to remove more bits because the
counter increments a number of times between reads. On a fast cpu,
fewer bits would have to be chopped off. That's all.
:I'd also like to see the description include the number of bits, rather
:than the mask, if we are using a mask.
:
:Thanks for taking the time to track this one down.
Well, I don't want to spend too much time on it because this was
incidental to other work I'm doing on -current. If you think it's worth
comitting I'll commit it, otherwise you can use it as a template for your
own fix/commit. It would be nice if some sort of solution were comitted
to the tree relatively soon.
-Matt
Matthew Dillon
<dillon@backplane.com>
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