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From: Ludovic Brenta <ludovic@ludovic-brenta.org>
Newsgroups: comp.lang.ada
Subject: Re: task model
Date: Thu, 15 Oct 2009 11:00:17 -0700 (PDT)
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Date: 2009-10-15T11:00:17-07:00
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Michael Tabak wrote on comp.lang.ada:
> I'm prototyping some tasking with multiple accepts, the code is as
> follows:
>
> with Ada.Text_Io;
> use Ada.Text_Io;
>
> procedure task_test is
>
> =A0 =A0procedure Process_Primary(node: in Integer) is
>
> =A0 =A0begin
>
> =A0 =A0 =A0 =A0Put_Line("This is number" & Integer'Image(node));
>
> =A0 =A0end Process_Primary;
>
> =A0 =A0task proc1 is
> =A0 =A0 =A0entry process1(node : Integer);
> =A0 =A0 =A0entry continue;
> =A0 =A0end proc1;
>
> =A0 =A0task body proc1 is
> =A0 =A0begin
>
> =A0 =A0 =A0accept process1( node : Integer) do
>
> =A0 =A0 =A0 =A0Process_Primary( node );
>
> =A0 =A0 =A0end;
>
> =A0 =A0 =A0accept continue do
> =A0 =A0 =A0 =A0Put_Line("Called Continue task1");
> =A0 =A0 =A0end;
>
> =A0 =A0end proc1;
>
> =A0 =A0task proc2 is
> =A0 =A0 =A0entry process2(node : Integer);
> =A0 =A0 =A0entry continue;
> =A0 =A0end proc2;
>
> =A0 =A0task body proc2 is
> =A0 =A0begin
>
> =A0 =A0 =A0accept process2( node : Integer) do
>
> =A0 =A0 =A0 =A0 =A0Process_Primary( node );
>
> =A0 =A0 =A0end;
>
> =A0 =A0 =A0accept continue do
> =A0 =A0 =A0 =A0Put_Line("Called Continue task2");
> =A0 =A0 =A0end;
>
> =A0 =A0end proc2;
>
> begin
> =A0 for i in 1..2 loop
> =A0 =A0proc1.process1(1);
> =A0 =A0proc2.process2(2);
> =A0 =A0proc1.continue;
> =A0 =A0proc2.continue;
> =A0 end loop;
> end task_test;
> -------------------------------------------------------------------------=
--------------------------------------------
>
> I get the out put I expect:
>
> This is number 1
> This is number 2
> Called Continue task1
> Called Continue task2
>
> But I also get the following error which I can't track down:
>
> raised TASKING_ERROR : s-tasren.adb:486

Your expectations are wrong :)

Your environment task contains a loop calling each task four times:
for each task the call sequence is processN, continue, processN,
continue.  But the tasks do not contain a loop, so they can accept
only the first two entry calls and then they terminate.  So the second
call to process1 raises Tasking_Error because task1 has terminated by
now.

HTH

--
Ludovic Brenta.