Le Fri, 27 Sep 2013, Tom Ridge a écrit :
> Dear caml-list,
> 
> I have a little program which creates a thread, and then sits in a loop:
> 
> --
> 
> let f () =
>   let _ = ignore (print_endline "3") in
>   let _ = ignore (print_endline "hello") in
>   let _ = ignore (print_endline "4") in
>   ()
> 
> let main () =
>   let _ = ignore (print_endline "1") in
>   let t = Thread.create f () in
>   (* let _ = Thread.join t in *)
>   let _ = ignore (print_endline "2") in
>   while true do
>     flush stdout;
>   done
> 
> let _ = main ()
> 
> --
> 
> I compile the program with the following Makefile clause:
> 
> test.byte: test.ml FORCE
> ocamlc -o $@ -thread unix.cma threads.cma $<
> 
> When I run the program I get the output:
> 
> 1
> 2
> 
> and the program then sits in the loop. I was expecting the output from
> f to show up as well. If you wait a while, it does. But you have to
> wait quite a while.
> 
> What am I doing wrong here? I notice that if I put Thread.yield in the
> while loop then f's output gets printed pretty quickly. But why should
> the while loop affect scheduling of f's thread?

I believe the main lock on the GC can only be released if you allocate
or call yield() explicitely. In this case, I suspect that flush does
neither, so the loop goes on and the f thread starves.

Please let more knowledgeable people correct me if I'm confused.

Cheers,

-- 
Simon