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Re: semantics of multithreading?

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On Saturday, June 15, 2013 6:50:03 AM UTC-7, sieg...@googlemail.com wrote:
> On Thursday, June 13, 2013 11:42:34 AM UTC-4, Martin Bonner wrote:
>
> > On Monday, June 10, 2013 8:23:21 PM UTC+1, sieg...@googlemail.com wrote:
>
> > > I am suspicious of the latter case because it could allow the
>
> > > compiler to introduce a deadlock or livelock in some programs.
>
> >
>
> > I don't see how.  The compiler can optimize in a way that eliminates
>
> > certain possible orderings, but if there is a deadlock in the ordering
>
> > it chooses then that can happen anyway.
>
>
>
> Example:
>
>
>
>    void f1() { while x.load() {}; }
>
>    void f2() { x.store(0); }
>
>    x.store(1);
>
>    p1 = fork(f1);
>
>    p2 = fork(f2);
>
>    p1.start(); p2.start();
>
>    p1.join(); p2.join();
>
>
>
> I would argue that the above program can terminate -- it is not livelocked.

You can argue whatever you like; the standard doesn't agree.

The standard is very clear on this; you may not *assume* that a thread
will ever execute past a certain point unless you use an explicit
ordering primitive like a thread ::join or a mutex.

Will this ever deadlock in real systems? Probably not. Does the
*standard* guarantee that it won't? Absolutely not.


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semantics of multithreading? siegebell@googlemail.com - 2013-06-10 12:23 -0700
  Re: semantics of multithreading? Jason McKesson <jmckesson@googlemail.com> - 2013-06-11 12:19 -0700
  Re: semantics of multithreading? Martin Bonner <martinfrompi@yahoo.co.uk> - 2013-06-13 08:42 -0700
    Re: semantics of multithreading? siegebell@googlemail.com - 2013-06-15 08:42 -0600
      Re: semantics of multithreading? Jason McKesson <jmckesson@googlemail.com> - 2013-06-16 19:58 -0600
        Re: semantics of multithreading? usenet@mkarcher.dialup.fu-berlin.de (Michael Karcher) - 2013-06-18 11:36 -0700
          Re: semantics of multithreading? siegebell@googlemail.com - 2013-06-23 19:19 -0600
        Re: semantics of multithreading? siegebell@googlemail.com - 2013-06-23 19:18 -0600

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