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From: =?ISO-8859-1?Q?Bj=F6rn_Lundin?= <b.f.lundin@gmail.com>
Newsgroups: comp.lang.ada
Subject: Re: assigning priority to task
Date: Wed, 24 Sep 2014 16:55:02 +0200
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Date: 2014-09-24T16:55:02+02:00
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On 2014-09-24 15:17, Stribor40 wrote:
> how is calling another task at the entry point different from main thread calling another function or procedure and passing parameters to those? sorry if question is dumb but I am just failing to see the difference....
> Is it because of tasks synchronization mechanism that calling tasks waits if another tasks is using things defined after accept statement?
> 

(Not compiled code)

task T is
  entry T1;
  entry T2;
end T


task body T is
begin

  loop
    select
      accept T1 do
        Put_Line ("rendez-vouz start");
        Put_Line ("Do_stuff that holds caller");
        Put_Line ("rendez-vouz stop");
      done
    or
      accept T1 do
        Put_Line ("rendez-vouz start");
        Put_Line ("rendez-vouz stop");
      done
      -- parallel execution from here
      Put_Line ("Do_stuff that DOES NOT hold caller");
      -- to here
    or
      terminate;
    end select;
  end loop;
end T



if main calls T.T1, the difference
compared with calling a procedure
T1 in package T is that the work is
performed in another thread and main waits until complete.
You do not get parallel execution.
You serialize work, but could use a protected object instead

however,

if main calls T.T2, the difference
compared with calling a procedure
T2 in package T is that the work is
performed in another thread and main is released right away,
so the T2 work is carried out while main continues.
You get _parallel_ execution.



--
Björn