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-- C954010.A

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--

-- OBJECTIVE:

--      Check that a requeue within an accept statement does not block.

--      This test uses: Requeue to an entry in a different task

--                      Parameterless call

--                      Requeue with abort

--

-- TEST DESCRIPTION:

--      In the Distributor task, requeue two successive calls on the entries

--      of two separate target tasks.  Verify that the target tasks are

--      run in parallel proving that the first requeue does not block

--      while the first target rendezvous takes place.

--

--      This series of tests uses a simulation of a transaction driven

--      processing system.  Line Drivers accept input from an external source

--      and build them into transaction records.  These records are then

--      encapsulated in message tasks which remain extant for the life of the

--      transaction in the system. The message tasks put themselves on the

--      input queue of a Distributor which, from information in the

--      transaction and/or system load conditions forwards them to other

--      operating tasks. These in turn might forward the transactions to yet

--      other tasks for further action.  The  routing is, in real life,

--      dynamic and unpredictable at the time of message generation. All

--      rerouting in this  model is done by means of requeues.

--

--      This test is directed towards the BLOCKING of the REQUEUE only

--      If the original caller does not block, the outcome of the test will

--      not be affected.  If the original caller does not continue after

--      the return, the test will not pass.

--      If the requeue gets placed on the wrong entry a failing test could

--      pass (eg. if the first message is delivered to the second

--      computation task and the second message to the first) - a check for

--      this condition is made in other tests

--

--

-- CHANGE HISTORY:

--      06 Dec 94   SAIC    ACVC 2.0

--

--!

with Report;

with ImpDef;

procedure C954010 is

   -- Mechanism to count the number of Message tasks completed

   protected TC_Tasks_Completed is

      procedure Increment;

      function  Count return integer;

   private

      Number_Complete : integer := 0;

   end TC_Tasks_Completed;

   --

   TC_Expected_To_Complete   : constant integer := 2;

   task type Message_Task;

   type acc_Message_Task is access Message_Task;

   task Line_Driver is

      entry Start;

   end Line_Driver;

   task Distributor is

      entry Input;

   end Distributor;

   task Credit_Computation is

      entry Input;

   end Credit_Computation;

   task Debit_Computation is

      entry Input;

      entry TC_Artificial_Rendezvous_1;      -- test purposes only

      entry TC_Artificial_Rendezvous_2;      -- test purposes only

   end Debit_Computation;

   -- Mechanism to count the number of Message tasks completed

   protected body TC_Tasks_Completed is

      procedure Increment is

      begin

         Number_Complete := Number_Complete + 1;

      end Increment;

      function Count return integer is

      begin

         return Number_Complete;

      end Count;

   end TC_Tasks_Completed;

   -- Assemble messages received from an external source

   --   Creates a message task for each and sends this to a Distributor

   --   for appropriate disposal around the network of tasks

   --      Such a task would normally be designed to loop continuously

   --      creating the messages as input is received.  Simulate this

   --      but limit it to two dummy messages for this test and allow it

   --      to terminate at that point

   --

   task body Line_Driver is

   begin

      accept Start;      -- Wait for trigger from main

      for i in 1..2 loop

         declare

            -- create a new message task

            N : acc_Message_Task := new Message_Task;

         begin

            -- preparation code

            null; -- stub

         end;   -- declare

      end loop;

   exception

      when others =>

         Report.Failed ("Unexpected exception in Line_Driver");

   end Line_Driver;

   task body Message_Task is

   begin

      -- Queue up on Distributor's Input queue

      Distributor.Input;

      -- After the required computations have been performed

      -- return the message appropriately (probably to an output

      -- line driver

      null;            -- stub

      -- Increment to show completion of this task

      TC_Tasks_Completed.Increment;

   exception

      when others =>

         Report.Failed ("Unexpected exception in Message_Task");

   end Message_Task;

   -- Dispose each input message to the appropriate computation tasks

   --    Normally this would be according to some parameters in the entry

   --    but this simple test is using parameterless entries.

   --

   task body Distributor is

     Last_was_for_Credit_Computation : Boolean := false;   -- switch

   begin

      loop

         select

            accept Input do

               -- Determine to which task the message should be

               -- distributed

               --      For this test arbitrarily send the first to

               --      Credit_Computation and the second to Debit_Computation

               if Last_was_for_Credit_Computation then

                  requeue Debit_Computation.Input with abort;

               else

                  Last_was_for_Credit_Computation := true;

                  requeue Credit_Computation.Input with abort;

               end if;

            end Input;

         or

            terminate;

         end select;

      end loop;

   exception

      when others =>

         Report.Failed ("Unexpected exception in Distributor");

   end Distributor;

   -- Computation task.  After the computation is performed the rendezvous

   -- in the original message task is completed.

   task body Credit_Computation is

   begin

      loop

         select

            accept Input do

               -- Perform the computations required for this message

               --

               null;     -- stub

               --   For the test:

               --   Artificially rendezvous with Debit_Computation.

               --   If the first requeue in Distributor has blocked

               --   waiting for the current rendezvous to complete then the

               --   second message will not be sent to Debit_Computation

               --   which will still be waiting on its Input accept.

               --   This task will HANG

               --

               Debit_Computation.TC_Artificial_Rendezvous_1;

               --

            end Input;

         or

            terminate;

         end select;

      end loop;

   exception

      when others =>

         Report.Failed ("Unexpected exception in Credit_Computation");

   end Credit_Computation;

   -- Computation task.  After the computation is performed the rendezvous

   -- in the original message task is completed.

   task body Debit_Computation is

      Message_Count      : integer := 0;

      TC_AR1_is_complete : Boolean := false;

   begin

      loop

         select

            accept Input do

               -- Perform the computations required for this message

               null;    -- stub

            end Input;

            Message_Count := Message_Count + 1;

         or

            -- Guard until the rendezvous with the message for this task

            -- has completed

            when Message_Count > 0 =>

            accept TC_Artificial_Rendezvous_1;    -- see comments in

                                                  -- Credit_Computation above

            TC_AR1_is_complete := true;

         or

            -- Completion rendezvous with the main procedure

            when TC_AR1_is_complete =>

            accept TC_Artificial_Rendezvous_2;

         or

            terminate;

         end select;

      end loop;

   exception

      when others =>

         Report.Failed ("Unexpected exception in Debit_Computation");

   end Debit_Computation;

begin -- c954010

   Report.Test ("C954010", "Requeue in an accept body does not block");

   Line_Driver.Start;

   -- Ensure that both messages were delivered to the computation tasks

   -- This shows that both requeues were effective.

   --

   Debit_Computation.TC_Artificial_Rendezvous_2;

   -- Ensure that the message tasks completed

   while (TC_Tasks_Completed.Count < TC_Expected_To_Complete) loop

      delay ImpDef.Minimum_Task_Switch;

   end loop;

   Report.Result;

end C954010;