Re: GC + thread

[Christophe Raffalli <Christophe.Raffalli@univ-savoie.fr>]

Max Skaller wrote:
> 
> Christophe Raffalli wrote:
> > This extension is also necessary (it is easy to have realistic examples
> > where the GC would collect much more thread with this extension).
> >
> > What do you think of that ?
> 
> Why is this necessary? In particular, because in/out channels have
> reduced functionality, I have opted to use Unix.file_descr instead:
> these are converted to/from in/out channels if necessary.

in/out channels are not necessary. As you create the pair, there is no
extra functionnality.
The point is just to help a GC extended to collect potentialy dead
thread: 

If a thread T is blocked while trying to read from channel A and there
is an active thread with a pointer on A, you can not collect the thread
T.

If a thread T is blocked while trying to read from channel A and there
is only active thread with a pointer on the in part of A, you can
collect the thread T : no thread will ever be able to write on channel A
and T will never wakeup. 

This situation arises in practice every time you have thread which will
only write (or read) on a given channel. Then it is better to let the GC
know this.

As the actual version of Ocaml can not collect threads, it is clear that
in/out channel are useless ...

But there are a lot of thread applications (like a virtual machine for
any process calculus like the pi-calculus) which really needs a GC
collecting thread in the way I described in my previous mail.



-- 
Christophe Raffalli
Université de Savoie
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tél: (33) 4 79 75 81 03
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mail: Christophe.Raffalli@univ-savoie.fr
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