Groups > comp.programming.threads > #1337

Re: condvars of ACE framwork - possible bug

Newsgroups	comp.programming.threads
Date	2013-02-06 20:01 -0800
References	<9c4fabd6-a4e1-4ef1-9301-5fe7ef5df016@googlegroups.com> <a665fcf7-0bab-4207-b265-dc84a90c0d59@googlegroups.com> <a171fec1-2833-4c0b-a89e-f1d0b0d6876a@e10g2000vbv.googlegroups.com> <5ded78d9-8988-45aa-8de0-ccc4b702f7e8@googlegroups.com>
Message-ID	<b2771477-2f19-412e-85e5-b30586c4f72c@fv9g2000vbb.googlegroups.com> (permalink)
Subject	Re: condvars of ACE framwork - possible bug
From	Michael Podolsky <michael.podolsky.69@gmail.com>

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On Feb 6, 10:39 pm, Codeplug <graham.gre...@charter.net> wrote:
> On Wednesday, February 6, 2013 9:36:29 PM UTC-5, Michael Podolsky wrote:
> > > If ACE condvars are anything like Posix condvars, then looping on a predicate condition should solve the problem. See page 165 here (pdf):http://www.cs.wustl.edu/~schmidt/PDF/ACE-tutorial.pdf
>
> > looping on a condition and condvar solves spurious wake-ups problem,
>
> > not lost wake-ups problem. If you meant anything else, could you
>
> > provide your code?
>
> I'm probably not understanding the stated issue then :) It would help me to understand if I had the scenario you describe in code. eg:
>
> condvar c
> mutex m
>
> Thread A:
> --------------------
> m.lock
> predicate=true
> c.signal
> m.unlock
> ...
> m.lock
> while (predicate)
>   c.wait(m)
> m.unlock
>
> Thread B:
> --------------------
> m.lock
> while (!predicate)
>   c.wait(m)
> predicate=false
> c.signal
> m.unlock
>
> This seems correct to me using Posix semantics, but this probably isn't the scenario you described.
>
> gg

I meant a bit different scenario in which thread A waits on condvar,
thread B then signals condvar and waits on it. But your example is Ok,
as for me. So what you wrote is presumably correct example of using
condvars.

What I mean is that ACE condvars are internally broken, it is not
about how to write application-level code with them, but about their
internal implementation which may be incorrect and lead to bugs even
with correct application-level usage.

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Thread

condvars of ACE framwork - possible bug Michael Podolsky <michael.podolsky.69@gmail.com> - 2013-02-04 22:38 -0800
  Re: condvars of ACE framwork - possible bug Codeplug <graham.greene@charter.net> - 2013-02-06 13:42 -0800
    Re: condvars of ACE framwork - possible bug Michael Podolsky <michael.podolsky.69@gmail.com> - 2013-02-06 18:36 -0800
      Re: condvars of ACE framwork - possible bug Codeplug <graham.greene@charter.net> - 2013-02-06 19:39 -0800
        Re: condvars of ACE framwork - possible bug Michael Podolsky <michael.podolsky.69@gmail.com> - 2013-02-06 20:01 -0800
          Re: condvars of ACE framwork - possible bug Codeplug <graham.greene@charter.net> - 2013-02-06 20:16 -0800
            Re: condvars of ACE framwork - possible bug Michael Podolsky <michael.podolsky.69@gmail.com> - 2013-02-06 20:30 -0800
              Re: condvars of ACE framwork - possible bug Codeplug <graham.greene@charter.net> - 2013-02-07 09:05 -0800
                Re: condvars of ACE framwork - possible bug Michael Podolsky <michael.podolsky.69@gmail.com> - 2013-02-07 19:27 -0800
  Re: condvars of ACE framwork - possible bug Noob <root@127.0.0.1> - 2013-02-07 11:54 +0100
    Re: condvars of ACE framwork - possible bug Michael Podolsky <michael.podolsky.69@gmail.com> - 2013-02-07 19:24 -0800

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