Re: Advice, tasking and hardware

["Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org>]

On 05/27/2016 05:25 PM, rieachus@comcast.net wrote:
> 
> package Shutdown is
>   task Suspend is
>     entry Stop;
>     entry Wait;
>   end Suspend;
> end Shutdown;
> ...
> package body Shutdown is
> begin
>  task body Suspend is
>  begin
>    accept Stop;
>    loop
>      select
>        accept Wait;
>      or
>        accept Stop; -- in case of multiple calls to Stop.
>      or
>        terminate;
>      end select;
>    end loop;
>  end Shutdown;

Is there any reason for this to be a task? I've always used a protected object:

package Shutdown is
   protected Control is
      procedure Time_To_Die;
      -- Tell the system to shut down

      function Time_To_Die return Boolean;
      -- Returns True if the system is shutting down

      entry Wait;
      -- Blocks until the system is shutting down
   private -- Control
      Shutting_Down : Boolean := False;
   end Control;
end Shutdown;

Procedure Time_To_Die sets Shutting_Down to True, function Time_To_Die returns
Shutting_Down, and Wait is null and has the barrier "when Shutting_Down".
Procedure Time_To_Die and Wait work the same as Stop and Wait. The function is
useful for sporadic tasks that block on an entry waiting for something to do.

-- 
Jeff Carter
"I'm a kike, a yid, a heebie, a hook nose! I'm Kosher,
Mum! I'm a Red Sea pedestrian, and proud of it!"
Monty Python's Life of Brian
77