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Re: Making one or more threads wait for another to produce a value or fail

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In article <is41d4$s5p$1@lust.ihug.co.nz>,
 Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> wrote:

> In message <alpine.DEB.2.00.1105311443530.28134@urchin.earth.li>, Tom 
> Anderson wrote:
> 
> > Penelope is a widow, or at least her husband isn't around any more 
> > (she's not sure which; long story). There are 108 suitors who would 
> > like to marry her. She hasn't decided which one she'll marry. So, 
> > the 108 suitors are sitting about waiting for her to decide. It's 
> > possible that instead of deciding to marry one of them, she'll 
> > deliver some other, exceptional, verdict (eg "turns out my husband 
> > is still alive, and will now murder you all").
> > 
> > Penelope is a thread, as are her suitors. Penelope has plenty to do 
> > after she delivers her verdict, so the verdict is not a return 
> > value - it's a value she'll pass to a method.

<https://groups.google.com/forum/#!topic/comp.lang.java.programmer/PvSa1FPX6as/discussion>

In this example, synchronization hinges on the entries of the protected 
object [1], verdict. The suitors queue on the obtain entry, waiting for 
the verdict. When penelope delivers the verdict, the barrier got_v is 
changed to allow the suitors to proceed. Ada protected types [2] are a 
common way to provide synchronized access to the private data of 
objects.

I'm wary of a too-literal translation; but, if I understand the memory 
consistency effects of CountDownLatch correctly, penelope could 
establish the verdict and invoke countDown(), knowing that any suitors 
returning form await() would see the correct value.

[1]<http://www.ada-auth.org/standards/12rm/html/RM-9-4.html>
[2]<http://www.adaic.org/resources/add_content/standards/95rat/rat95html/rat95-p1-2.html#9>
[3]<http://download.oracle.com/javase/6/docs/api/java/util/concurrent/CountDownLatch.html>

-- 
John B. Matthews
trashgod at gmail dot com
<http://sites.google.com/site/drjohnbmatthews>

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Making one or more threads wait for another to produce a value or fail Tom Anderson <twic@urchin.earth.li> - 2011-05-31 15:00 +0100
  Re: Making one or more threads wait for another to produce a value or fail Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-05-31 07:14 -0700
    Re: Making one or more threads wait for another to produce a value or fail Tom Anderson <twic@urchin.earth.li> - 2011-05-31 16:46 +0100
      Re: Making one or more threads wait for another to produce a value or fail Deeyana <d.awlberg@hotmail.invalid> - 2011-05-31 19:23 +0000
        Re: Making one or more threads wait for another to produce a value or fail Tom Anderson <twic@urchin.earth.li> - 2011-06-01 22:12 +0100
      Re: Making one or more threads wait for another to produce a value or fail Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-05-31 20:45 -0700
        Re: Making one or more threads wait for another to produce a value or fail Patricia Shanahan <pats@acm.org> - 2011-05-31 21:37 -0700
          Re: Making one or more threads wait for another to produce a value or fail Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-06-01 07:18 -0700
            Re: Making one or more threads wait for another to produce a value or fail Patricia Shanahan <pats@acm.org> - 2011-06-01 09:01 -0700
        Re: Making one or more threads wait for another to produce a value or fail Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-06-01 16:40 +1200
          Re: Making one or more threads wait for another to produce a value or fail "John B. Matthews" <nospam@nospam.invalid> - 2011-06-01 11:22 -0400
            Re: Making one or more threads wait for another to produce a value or fail Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-06-02 10:15 +1200
              Re: Making one or more threads wait for another to produce a value or fail "John B. Matthews" <nospam@nospam.invalid> - 2011-06-01 21:38 -0400
        Re: Making one or more threads wait for another to produce a value or fail Tom Anderson <twic@urchin.earth.li> - 2011-06-01 22:07 +0100
          Re: Making one or more threads wait for another to produce a value or fail Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-06-01 22:46 -0700
  Re: Making one or more threads wait for another to produce a value or fail markspace <-@.> - 2011-05-31 08:26 -0700
    Re: Making one or more threads wait for another to produce a value or fail Tom Anderson <twic@urchin.earth.li> - 2011-05-31 19:13 +0100
  Re: Making one or more threads wait for another to produce a value or fail Patricia Shanahan <pats@acm.org> - 2011-05-31 09:06 -0700
    Re: Making one or more threads wait for another to produce a value or fail Paul Cager <paul.cager@googlemail.com> - 2011-05-31 10:08 -0700
      Re: Making one or more threads wait for another to produce a value or fail Patricia Shanahan <pats@acm.org> - 2011-05-31 10:39 -0700
        Re: Making one or more threads wait for another to produce a value or fail Paul Cager <paul.cager@googlemail.com> - 2011-05-31 16:24 -0700
  Re: Making one or more threads wait for another to produce a value or fail Lawrence D'Oliveiro <ldo@geek-central.gen.new_zealand> - 2011-06-01 12:33 +1200
    Re: Making one or more threads wait for another to produce a value or fail "John B. Matthews" <nospam@nospam.invalid> - 2011-06-01 00:38 -0400
  Re: Making one or more threads wait for another to produce a value or fail markspace <-@.> - 2011-06-02 14:10 -0700
    Re: Making one or more threads wait for another to produce a value or fail markspace <-@.> - 2011-06-02 14:25 -0700
    Re: Making one or more threads wait for another to produce a value or fail Patricia Shanahan <pats@acm.org> - 2011-06-02 14:43 -0700

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