Re: select delay; then abort... in Annex E

["Alex R. Mosteo" <devnull@mailinator.com>]

Dr. Adrian Wrigley wrote:

> On Mon, 02 Oct 2006 09:33:46 +0200, Alex R. Mosteo wrote:
> 
>> Dr. Adrian Wrigley wrote:
>> 
>>> Hi guys,
>>> 
>>> Things are now working *much* better with my Annex E setup here.
>>> 
>>> The server hasn't been totally free of problems, but at least I
>>> can't point the finger at Glade this time ;-)
>>> 
>>> I wanted to limit the execution time of a partition. So I tried
>>> something like:
>>> 
>>> select
>>>    delay 10.0;
>>>    Complain;
>>> then abort
>>>    RemoteProcedure;
>>> end select;
>>> 
>>> the intent was that the partition would terminate if the
>>> RemoteProcedure exceeded the alloted 10s of execution time.
>>> 
>>> Unfortunately, what happens is that the code runs for the full
>>> duration of the RemoteProcedure (say 10 minutes), then it
>>> invokes Complain, finally exiting.
>> 
>> This is the behavior you get if you try the same with a Text_Io.Get_Line
>> call (that indeed is potentially blocking IO).
> 
> The strange thing is that the statement sequence in the abortable
> part executes right to the end (if there are several).  I would
> have thought the abort would happen as soon as it completes
> a blocking operation.
> 
> Regardless, it's a real nuisance if any remote call can
> hold up a task indefinitely.  I need real-time operation
> of my program (although at a *much* lower speed/latency
> than most software called "real-time").
> 
>>> Why can't the RemoteProcedure be aborted?  Is it because it
>>> is a blocking operation (E.4.17)? E.4.13 suggests the construct
>>> can be aborted (cancelling the remote operation), but the
>>> above code suggests it can't.
>>> 
>>> Is there a way to get my partition to terminate regardless
>>> of outstanding remote calls?
>> 
>> An idea is to do it the dirty way, creating a new task to do the call and
>> aborting it the rough way. I've taken a quick look at ARM05/9.8.5 but
>> couldn't conclude anything.
> 
> I had already tried this.  I used abort on a named task.  It didn't
> seem to do what I expected.
> 
> What happens is that the RCI call continues to completion.  All
> subsequent delay statements in the task take minimal time(!),
> but the task continues to run.  It can successfully call RCI
> units, and proceeds as normal (other than the instant delay statements)
> until it completes.
> 
> I have put together a test case which illustrates this.
> 
> Once a task has executed a RCI call, it cannot be aborted
> properly at all :(  (GNAT GPL 2006, Linux, FC5 i686)
> 
> Can anyone out there try this example for me please?
> (correct behaviour is to count to about six, then the program
> terminates. <example below>

I'm sorry, I'm leaving for a two weeks trip and don't have glade installed
nor the time to thinker right now. I'm using linux too, anyways.

> 
> Thanks.
> --
> Adrian
> 
> 
> $ ls *.ad[sb] *cfg
> a.adb  a.ads  cmain.adb  dist.cfg
> $ gnatdist -q dist.cfg
> $ cmain  # Illustrates incorrect behaviour
> J= 1
> J= 2
> J= 3
> J= 4
> Abort to be called
> Abort returned.  The program should stop shortly.
> J= 5
> J= 6
> <all the way up to 100>
> M= 1
> <all the way up to ten>
> $ cat *.ad[sb] *cfg
> package body A is
> 
>    function Next return Integer is
>    begin
>       return 0;
>    end Next;
> 
> end A;
> package A is
> 
>    pragma Remote_Call_Interface;
>    pragma All_Calls_Remote;
>    function Next return Integer;
> 
> end A;
> with Text_IO;
> with A;
> 
> procedure CMain is
> 
>    task AbortTest;
>    task body AbortTest is
>       X : Integer;
>    begin
> 
>       for J in 1 .. 100 loop
> 
>          X := A.Next; -- Delete this line for correct behaviour
>          delay 1.0;
> 
>          Text_IO.Put_Line ("J=" & Integer'Image (J));
> 
>       end loop;
> 
>       for M in 1 .. 10 loop
>          for K in 1 .. 600_000_000 loop
>             null;
>          end loop;
>          Text_IO.Put_Line ("M=" & Integer'Image (M));
>       end loop;
> 
>    end AbortTest;
> 
> begin
> 
>    delay 5.0;
> 
>    Text_IO.Put_Line ("Abort to be called");
>    abort AbortTest;
>    Text_IO.Put_Line ("Abort returned.  The program should stop shortly.");
> 
> end CMain;
> configuration Dist is
> 
>   APart : Partition := (A, CMain);
>   procedure CMain is in APart;
> 
> end Dist;
> $