Re: [Boost-users] Re: Re: Re: Semaphore and barriers for boost-threads?

From: Victor A. Wagner, Jr. (vawjr_at_[hidden])
Date: 2004-02-19 16:10:59

At Thursday 2004-02-19 00:08, you wrote:
>Craig Rodrigues wrote:
>
> >> Look the the phrase "Much experience with semaphores shows" and futher
> >> paragraphs. In essense, it's says that semaphores are for signal handlers
> >> and for inter-process synchronization and discourages their use anywhere
> >> else.
> >
> > That's an interesting link, thanks!
> > I don't interpret the text in the same way that you do, but
> > maybe I am not understanding something properly.
>
>Maybe I don't, either. The standard cannot make definitive statements that
>"semaphore is bad". Folks on comp.programming.threads newsgroup seem to
>make such statements in more clear language ;-)
>
> > Further down from "Much experience with semaphores shows",
> > there is this text:
> >
> > "Counting semaphores are well matched to dealing with producer/consumer
> > problems, including those that might exist between threads of
> > different processes, or between a signal handler and a thread. In
> > the former case, there may be little or no memory shared by the
> > processes; in the latter case, one is not communicating between
> > co-equal threads, but between a thread and an interrupt-like entity.
> > It is for these reasons that IEEE Std 1003.1-2001 allows semaphores
> > to be used by threads."
>
>Doesn't it say that semaphores are retained for inter-process communication
>and for signal handlers?
>
> > This is the use-case that I am interested in.
>
>Which one? Signal handler or inter-process communication?

does it really matter? semaphores are useful (and can be misused, like a 
lot of other things in life).  Why the resistance to putting them in?

>- Volodya
>
>
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Victor A. Wagner Jr.      http://rudbek.com
The five most dangerous words in the English language:
               "There oughta be a law"