Re: [Caml-list] Why systhreads?

[Sven Luther <luther@dpt-info.u-strasbg.fr>]

On Tue, Nov 26, 2002 at 10:02:54AM +0100, Xavier Leroy wrote:
> Blair Zajac wrote:
> 
> > To summarize, for (2) system threads are required and and you can't
> > prevent blocking with user level threads easily or at all.  For (3),
> > making the Ocaml system support SMP is "Too complex; too hard to
> > debug" and SMP boxes aren't all that popular.
> > Aren't these contradictory statements?
> > 
> > For Ocaml to support a Ocaml program to have one thread to block on a
> > system call and to allow other threads to continue, doesn't this support
> > SMP?  Does Ocaml support this?
> 
> No to the first question.  Yes to the second.
> 
> By "supporting SMP", I mean having several threads executing Caml code
> in parallel, thus using the Caml runtime system in a concurrent fashion.
> This is the hard part.  
> 
> In the current implementation of systhreads, the Caml executor and
> runtime system is one big critical section: at most one thread can
> execute Caml code at a given time, but arbitrarily many other threads
> can be blocked on I/O (and thus isn't calling the Caml runtime system).
> Each thread leaves the critical section before calling a potentially
> blocking I/O operation, and re-enters it when the I/O completes.

In the case i have a multi-threaded lablgtk executable, having ine
thread managing the interface and the other running programs, that even
if i had a way of killing a thread (or setting a mutex or whatever to
signal it to stop), that if the running thread is looping, i will never
be able to execute the interface thread which will (trough a callback)
set the mutex to the stop option, because the running thread doesn't do
blocking IO ?

Mmm, checking the mutex is a blocking IO though, isn't it ? 

keeping the GUI alive even if some other stuff is taking time or looping
forever is a nice application of threading support.

Friendly,

Sven Luther
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