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From: kcline17@hotmail.com (Kevin Cline)
Newsgroups: comp.lang.ada
Subject: Re: rendez-vous underlying mechanism
Date: 8 Apr 2002 10:05:27 -0700
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Richard Riehle <richard@adaworks.com> wrote in message news:<3CA2A827.11140295@adaworks.com>...
> Kevin Cline wrote:
> 
> > "Bozo" <gri_nob@yahoo.com> wrote in message news:<a7pk89$kj4$1@bcarh8ab.ca.nortel.com>...
> > > Hi all,
> > >
> > > I'm sorry I wasn't clear enough.
> > > I don't use ADA at the moment but I was a brave ADA programmer once.
> > > I use C at the moment and I have a case where synchronous rendez-vous would
> > > be better that traditional asynchrounous intertask communications.
> > >
> > > Does anyone have an idea how to implement that in C with semaphores for
> > > example ?
> >
> > This depends on the underlying OS.  If you are using pthreads,
> > then see the manual entry for pthread_cond_wait.
> 
> This approach, of course, does not come close to the capabilities
> already built-in to the Ada tasking model.    Ever heard of protected
> types.

I know that.  However, in a hosted environment, the imperfect
mapping between the Ada tasking model and the underlying OS facilities
can catch programmers by surprise.  I was certainly surprised 
when I attempted to create a separate task for I/O but found that
all tasks blocked anyway because they were mapped to a single Unix thread. 
On that implementation Ada multi-tasking was uselsss for solving
problems routinely handled with Posix threads.