Re: Freezing a task

[Adam Beneschan <adam@irvine.com>]

On Nov 17, 7:33 am, "Rego, P." <pvr...@gmail.com> wrote:
> Is is possible to freeze a task?
>
> I mean, if I have a task
>
> task body My_Task is
> begin
>   accept Start;
>   loop
>     Put ("1");
>     Put ("2");
>     Put ("3");
>     ...
>     Put ("n");
>   end loop;
> end My_Task;
>
> is there a way that I can "freeze" the task in its current state? If, for instance, the execution finished executing Put ("2");, how can I freeze it and later I can turn it to continue? I want to provoque a freeze from outside the task, and also from outside, order it to continue.
>
> I could sure implement, if I had the spec like
>
> type State_Type is
>   (RUN,
>    FROZEN);
>
> task type My_Task (State : State_Type) is
>    entry Start;
> end My_Task;
> --
>
> the body:
>
> task body My_Task is
> begin
>   accept Start;
>   loop
>     Put ("1");
>     Put ("2");
>     Put ("3");
>     ...
>     Put ("n");
>
>     loop
>      if State = RUN then exit; end if;
>     end loop;
>   end loop;
> end My_Task;
>
> but it would not be the case because I had to wait for the nth Put instruction line (i.e., the task would not be actually frozen, because the inside loop would be running).
>
> And T.E.D. from stackoverflow suggested me something that I could infer as
>
> task type My_Task (Start : Start_Type) is
>    entry Start;
>    entry Run;
> end My_Task
> --
> task body My_Task is
> begin
>   accept Start;
>   loop
>     Put ("1");
>     Put ("2");
>     Put ("3");
>     ...
>     Put ("n");
>
>     if State = FROZEN then
>        accept Run;
>        State := RUN;
>     end if;
>   end loop;
> end My_Task;
>
> Is there a more elegant way to do this? Maybe some procedure My_Task.FreezeNow in a unknown (by me) package? Thanks

Aside from the other suggestions, you might want to look into
Ada.Synchronous_Task_Control and Ada.Asynchronous_Task_Control.  I'm
not really clear on what you're trying to accomplish, so it's hard for
me to say whether those are appropriate solutions for you.  I think
that the other methods that have been suggested--an entry call on
another task or on a protected object, or an ACCEPT statement--would
be preferable if they get the job done.

                               -- Adam