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Groups > comp.programming.threads > #2233

Re: About lockfree and waitfree... (2nd try)

From Stephen Fuld <SFuld@alumni.cmu.edu.invalid>
Newsgroups comp.programming.threads, comp.programming, comp.arch
Subject Re: About lockfree and waitfree... (2nd try)
Date 2014-04-23 13:21 -0700
Organization A noiseless patient Spider
Message-ID <lj97cc$hfk$1@dont-email.me> (permalink)
References <lif821$inj$1@news.albasani.net> <lj659h$u1s$1@dont-email.me> <lj66c0$6ji$1@dont-email.me> <lj933b$i85$1@dont-email.me> <lj94gr$c41$1@needham.csi.cam.ac.uk>

Cross-posted to 3 groups.

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On 4/23/2014 12:32 PM, Nick Maclaren wrote:
> In article <lj933b$i85$1@dont-email.me>,
> Stephen Fuld  <SFuld@Alumni.cmu.edu.invalid> wrote:
>>
>> I have been thinking about this.  Does the following work?
>
> No.  Sorry.
>
>> To solve the scalability problem, you have multiple incrementing counter
>> registers, perhaps one per core, or one per few cores with arbitration,
>> that are distributed around the chip, but synchronized quite closely,
>> say at the sub nanosecond level.  ...
>
> First problem.  How?  That's probably not impossible, but it's
> not obviously possible, either.

Well, I am not a circuits guy, but I am basing this on Ivan's post, 
quoted below.

>  So the clocks on the cores on a single chip need to be
> synchronized sub-nanosecond (easy),



>
>> Does this solve the TAN problem, at least for a supposed 10,000 core chip?
>
> No, for two reasons:
>
>      That won't deliver temporarily consistent timestamps, which are
> the critical requirement for that facilities.  That is essentially
> sequential consistency on the timestamps.

I thought the TAN problem was stated as no two people get the same 
number but the numbers need not be strictly sequential (i.e. there nay 
be holes), and no requester has enough priority to starve another 
requester.  BTW, did you mean "temporally"?


>      What many such algorithms need is a timer that can be used to
> determine in which order memory accesses were made.  I think those
> are a hopeless idea, but that doesn't stop people wanting them.

I don't think that is what Ivan asked for, but I agree that my proposal 
doesn't solve that problem.



-- 
  - Stephen Fuld
(e-mail address disguised to prevent spam)

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Thread

About lockfree and waitfree... aminer <aminer@toto.net> - 2014-04-13 19:54 -0700
  Re: About lockfree and waitfree... "Chris M. Thomasson" <no@spam.invalid> - 2014-04-13 19:38 -0700
    Re: About lockfree and waitfree... "Chris M. Thomasson" <no@spam.invalid> - 2014-04-13 19:47 -0700
      Re: About lockfree and waitfree... aminer <aminer@toto.net> - 2014-04-13 22:56 -0700
      Re: About lockfree and waitfree... "Chris M. Thomasson" <no@spam.invalid> - 2014-04-14 14:08 -0700
        Re: About lockfree and waitfree... "Chris M. Thomasson" <no@spam.invalid> - 2014-04-14 14:23 -0700
          Re: About lockfree and waitfree... Ivan Godard <ivan@ootbcomp.com> - 2014-04-14 16:27 -0700
          Re: About lockfree and waitfree... (2nd try) Ivan Godard <ivan@ootbcomp.com> - 2014-04-14 16:29 -0700
            Re: About lockfree and waitfree... (2nd try) "Chris M. Thomasson" <no@spam.invalid> - 2014-04-15 10:04 -0700
              Re: About lockfree and waitfree... (2nd try) Ivan Godard <ivan@ootbcomp.com> - 2014-04-15 10:34 -0700
                Re: About lockfree and waitfree... (2nd try) "Chris M. Thomasson" <no@spam.invalid> - 2014-04-17 16:35 -0700
                Re: About lockfree and waitfree... (2nd try) Ivan Godard <ivan@ootbcomp.com> - 2014-04-17 17:04 -0700
                Re: About lockfree and waitfree... (2nd try) nmm@needham.csi.cam.ac.uk (Nick Maclaren) - 2014-04-18 09:54 +0100
                Re: About lockfree and waitfree... (2nd try) Ivan Godard <ivan@ootbcomp.com> - 2014-04-18 02:31 -0700
                Re: About lockfree and waitfree... (2nd try) nmm@needham.csi.cam.ac.uk (Nick Maclaren) - 2014-04-18 11:56 +0100
                Re: About lockfree and waitfree... (2nd try) rpw3@rpw3.org (Rob Warnock) - 2014-04-18 11:26 +0000
                Re: About lockfree and waitfree... (2nd try) Ivan Godard <ivan@ootbcomp.com> - 2014-04-18 13:30 -0700
                Re: About lockfree and waitfree... (2nd try) "Chris M. Thomasson" <no@spam.invalid> - 2014-04-21 14:25 -0700
                Re: About lockfree and waitfree... (2nd try) "Chris M. Thomasson" <no@spam.invalid> - 2014-04-21 14:31 -0700
                Re: About lockfree and waitfree... (2nd try) Ivan Godard <ivan@ootbcomp.com> - 2014-04-21 14:53 -0700
                Re: About lockfree and waitfree... (2nd try) "Chris M. Thomasson" <no@spam.invalid> - 2014-04-22 14:21 -0700
                Re: About lockfree and waitfree... (2nd try) "Chris M. Thomasson" <no@spam.invalid> - 2014-04-22 14:36 -0700
                Re: About lockfree and waitfree... (2nd try) Ivan Godard <ivan@ootbcomp.com> - 2014-04-22 15:30 -0700
                Re: About lockfree and waitfree... (2nd try) "Chris M. Thomasson" <no@spam.invalid> - 2014-05-01 00:48 -0700
                Re: About lockfree and waitfree... (2nd try) "Chris M. Thomasson" <no@spam.invalid> - 2014-05-25 13:16 -0700
                Re: About lockfree and waitfree... (2nd try) "Chris M. Thomasson" <no@spam.invalid> - 2014-04-21 14:34 -0700
                Re: About lockfree and waitfree... (2nd try) Robert Wessel <robertwessel2@yahoo.com> - 2014-04-21 16:42 -0500
                Re: About lockfree and waitfree... (2nd try) Ivan Godard <ivan@ootbcomp.com> - 2014-04-21 15:02 -0700
                Re: About lockfree and waitfree... (2nd try) nmm@needham.csi.cam.ac.uk (Nick Maclaren) - 2014-04-22 09:05 +0100
                Re: About lockfree and waitfree... (2nd try) Stephen Fuld <SFuld@alumni.cmu.edu.invalid> - 2014-04-22 09:27 -0700
                Re: About lockfree and waitfree... (2nd try) Ivan Godard <ivan@ootbcomp.com> - 2014-04-22 09:45 -0700
                Re: About lockfree and waitfree... (2nd try) nmm@needham.csi.cam.ac.uk (Nick Maclaren) - 2014-04-22 18:08 +0100
                Re: About lockfree and waitfree... (2nd try) Stephen Fuld <SFuld@alumni.cmu.edu.invalid> - 2014-04-23 12:08 -0700
                Re: About lockfree and waitfree... (2nd try) nmm@needham.csi.cam.ac.uk (Nick Maclaren) - 2014-04-23 20:32 +0100
                Re: About lockfree and waitfree... (2nd try) Stephen Fuld <SFuld@alumni.cmu.edu.invalid> - 2014-04-23 13:21 -0700
                Re: About lockfree and waitfree... (2nd try) nmm@needham.csi.cam.ac.uk (Nick Maclaren) - 2014-04-23 21:51 +0100
                Re: About lockfree and waitfree... (2nd try) Chris Gray <cg@GraySage.COM> - 2014-04-24 10:53 -0600
                Re: About lockfree and waitfree... (2nd try) nmm@needham.csi.cam.ac.uk (Nick Maclaren) - 2014-04-24 18:02 +0100
                Re: About lockfree and waitfree... (2nd try) Stephen Fuld <SFuld@alumni.cmu.edu.invalid> - 2014-04-25 13:39 -0700
                Re: About lockfree and waitfree... (2nd try) "Chris M. Thomasson" <no@spam.invalid> - 2014-04-22 22:08 -0700
            Re: About lockfree and waitfree... (2nd try) George Neuner <gneuner2@comcast.net> - 2014-04-17 21:15 -0400
              Re: About lockfree and waitfree... (2nd try) George Neuner <gneuner2@comcast.net> - 2014-04-17 21:25 -0400
                Re: About lockfree and waitfree... (2nd try) Ivan Godard <ivan@ootbcomp.com> - 2014-04-17 19:17 -0700
                Re: About lockfree and waitfree... (2nd try) George Neuner <gneuner2@comcast.net> - 2014-04-18 00:46 -0400
              Re: About lockfree and waitfree... (2nd try) Ivan Godard <ivan@ootbcomp.com> - 2014-04-17 18:52 -0700
    Re: About lockfree and waitfree... aminer <aminer@toto.net> - 2014-04-13 22:54 -0700

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