Are delay statements abortable?

Are delay statements abortable?

[davidb42]

Are delay statements interruptable/abortable?

I was expecting delay statements in tasks (or in the abortable part of
an asynchronous select construct) to be brought to a premature end on
aborting the task (or on the triggering event).

However, in the Ada implementation I am using, the abortion only seems
to take effect at the expiry of the delay.

For example, in the program below, the main task completes after 25
seconds, but the dependent task (and thus the program as a whole)
doesn't terminate until 40 seconds (at expiry of the 2nd 20 second
delay).

Is this right?
	David Bowerman
	CSC Australia.

   **************************************************************
with Text_IO;
procedure Test_Abort_of_Delay is

  task Dependent_Task;
  task body Dependent_Task is
  begin
    Text_IO.Put_Line ("Starting dependent task.");

    delay 20.0;
    Text_IO.Put_Line ("20 second delay has completed.");
    delay 20.0;
    Text_IO.Put_Line ("40 second delay has completed.");
    delay 20.0;
    Text_IO.Put_Line ("60 second delay has completed.");
    delay 20.0;
    Text_IO.Put_Line ("80 second delay has completed.");

    Text_IO.Put_Line ("Completing dependent task.");
  end Dependent_Task;

begin
  -- Main task
  Text_IO.Put_Line ("Starting main task.");

  delay 25.0;
  abort Dependent_Task;

  Text_IO.Put_Line ("Completing main task.");
end Test_Abort_of_Delay;


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Re: Are delay statements abortable?

[Ross]

I don't believe they are in ada terms, but you could always pull the
plug.....
R.

davidb42@my-deja.com wrote:

> Are delay statements interruptable/abortable?
>
> I was expecting delay statements in tasks (or in the abortable part of
> an asynchronous select construct) to be brought to a premature end on
> aborting the task (or on the triggering event).
>
> However, in the Ada implementation I am using, the abortion only seems
> to take effect at the expiry of the delay.
>
> For example, in the program below, the main task completes after 25
> seconds, but the dependent task (and thus the program as a whole)
> doesn't terminate until 40 seconds (at expiry of the 2nd 20 second
> delay).
>
> Is this right?
>         David Bowerman
>         CSC Australia.
>
>    **************************************************************
> with Text_IO;
> procedure Test_Abort_of_Delay is
>
>   task Dependent_Task;
>   task body Dependent_Task is
>   begin
>     Text_IO.Put_Line ("Starting dependent task.");
>
>     delay 20.0;
>     Text_IO.Put_Line ("20 second delay has completed.");
>     delay 20.0;
>     Text_IO.Put_Line ("40 second delay has completed.");
>     delay 20.0;
>     Text_IO.Put_Line ("60 second delay has completed.");
>     delay 20.0;
>     Text_IO.Put_Line ("80 second delay has completed.");
>
>     Text_IO.Put_Line ("Completing dependent task.");
>   end Dependent_Task;
>
> begin
>   -- Main task
>   Text_IO.Put_Line ("Starting main task.");
>
>   delay 25.0;
>   abort Dependent_Task;
>
>   Text_IO.Put_Line ("Completing main task.");
> end Test_Abort_of_Delay;
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.

Re: Are delay statements abortable?

[susan satnford]

davidb42 wrote:
> 
> 
> Are delay statements interruptable/abortable?
> yes they are
> I was expecting delay statements in tasks (or in the abortable part of
> an asynchronous select construct) to be brought to a premature end on
> aborting the task (or on the triggering event).
> 
> However, in the Ada implementation I am using, the abortion only seems
> to take effect at the expiry of the delay.
> 
> For example, in the program below, the main task completes after 25
> seconds, but the dependent task (and thus the program as a whole)
> doesn't terminate until 40 seconds (at expiry of the 2nd 20 second
> delay).
> 
> Is this right?
> David Bowerman
> CSC Australia.
> 
>    **************************************************************
> with Text_IO;
> procedure Test_Abort_of_Delay is
> 
>   task Dependent_Task;
>   task body Dependent_Task is
>   begin
>     Text_IO.Put_Line ("Starting dependent task.");
> 
>     delay 20.0;
>     Text_IO.Put_Line ("20 second delay has completed.");
>     delay 20.0;
>     Text_IO.Put_Line ("40 second delay has completed.");
>     delay 20.0;
>     Text_IO.Put_Line ("60 second delay has completed.");
>     delay 20.0;
>     Text_IO.Put_Line ("80 second delay has completed.");
> 
>     Text_IO.Put_Line ("Completing dependent task.");
>   end Dependent_Task;
> 
> REMOVED INCLUDED FILE Test_Abort_of_Delay;
> 
> 
> Sent via Deja.com http://www.deja.com/
> Before you buy.


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Re: Are delay statements abortable?

[Tucker Taft]

davidb42@my-deja.com wrote:
> 
> Are delay statements interruptable/abortable?

Yes.

> 
> I was expecting delay statements in tasks (or in the abortable part of
> an asynchronous select construct) to be brought to a premature end on
> aborting the task (or on the triggering event).

They should be.
> 
> However, in the Ada implementation I am using, the abortion only seems
> to take effect at the expiry of the delay.

This would not qualify as a "real-time-systems-annex" supporting
implementation in Ada 95.  "Real-time" implementations are required
to abort preemptively in Ada 95 (see RM95 D.6(2)).
> 
> For example, in the program below, the main task completes after 25
> seconds, but the dependent task (and thus the program as a whole)
> doesn't terminate until 40 seconds (at expiry of the 2nd 20 second
> delay).
> 
> Is this right?

In a non-real-time implementation, this is "correct" but not particularly
helpful.  In a "real-time" Ada 95 implementation, this would be incorrect.

>         David Bowerman
>         CSC Australia.
-- 
-Tucker Taft   stt@averstar.com   http://www.averstar.com/~stt/
Technical Director, Distributed IT Solutions  (www.averstar.com/tools)
AverStar (formerly Intermetrics, Inc.)   Burlington, MA  USA