Re: GNAT and Tasklets

[vincent.diemunsch@gmail.com]

Le jeudi 18 décembre 2014 12:19:50 UTC+1, Dmitry A. Kazakov a écrit :
> On Thu, 18 Dec 2014 02:32:44 -0800 (PST), vincent.diemunsch@gmail.com
> wrote:
> 
> > Finaly, I really hope that the new version of the langage will keep Ada
> > simple and add "intelligence" in compilers and not add different new
> > features with :
> > - tasks for kernel threads
> > - coroutines or tasklets for user-level threads
> > - jobs for lightweight threads,
> > because this would be a major conceptual regression. I believe that
> > aspects on tasks could be an inelegant but decent way to solve the
> > problem.
> 
> Ideally yes, but if you consider the implications, you will have to
> reconsider protected actions and rendezvous. E.g. a protected action
> interlocking co-routines driven by the same thread do not need locking. Do
> you want to get advantage from this? Or, a rendezvous between them is a
> deadlock? Statically resolved? What with exception propagation on both
> ends? Forbidden? etc.
> 
> -- 
> Regards,
> Dmitry A. Kazakov
> http://www.dmitry-kazakov.de

yes, this is not a trivial issue. It needs a real study.

It would be interesting to do a little survey on existing code using tasking.
I have the impression that only tasks at Library level do rendez-vous and protected object synchronisation, and local tasks, most of the time, are limited to a rendez-vous with their parent task at the beginning or at the end. So maybe we should put restrictions on local tasks, so that we can map them to jobs.

This situation can be compared to Ravenscar restrictions, that allowed to use
fast, predictable tasking.

Kind regards,

Vincent