Re: task activation

[Robert A Duff <bobduff@world.std.com>]

"Matthew Heaney" <matthew_heaney@acm.org> writes:

> It is my understanding that a task "activates" when you hit the begin 
> part of the block in which the task is declared:
> 
> procedure Main is
>   task O is ...
>   task body O is ...;
> begin
>   <whatever>
> end Main;
> 
> In this example, task O activates when procedure Main reaches its begin.
> 
> Now, suppose we wanted to activate the task earlier than that.  Let's
> declare O in a nested package:
> 
> procedure Main is
>   package P is
>     task O is ...;
>   end;
>   package body P is
>     task body O is ...;
>   end;
> begin
>   <whatever>
> end;
> 
> 
> Does task O activate when
> 
> 1) the elaboration of nested package P completes (hit the begin part of
> P's body); that is, prior to hitting the begin part of Main.  Or,
> 
> 2) no, the nesting doesn't matter, and O still activates when you hit
> the begin part of procedure Main.

Number 1.

> Another question: suppose package P is a library level package (and
> therefore task O is a library level task).  Does O get activated when
> 
> 1) you hit the begin part of P's body; that is, prior to hitting the
> begin part of Ada main subprogram Main?  Or,
> 
> 2) no, the library-levelness doesn't matter, and O still is activated
> when you hit the begin part of the Ada main.

Number 1 again.  If you have a bunch of such packages, they will get
elaborated in some order that depends on with clauses and various
pragmas -- but when you elaborate the package body, the tasks therein
will be activated.

Another way to control the timing of activation is to put the task in
the heap -- then, an allocator causes the activation, and you can put
that allocator whereever you like.

- Bob