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-- C954A02.A

--

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--*

--

-- OBJECTIVE:

--      Check that if a task requeued with abort on a protected entry queue

--      is aborted, the protected entry call is canceled and the aborted

--      task becomes completed.

--

-- TEST DESCRIPTION:

--      Declare a protected type which simulates a printer device driver

--      (foundation code).

--

--      Declare a task which simulates a printer server for multiple printers.

--

--      For the protected type, declare an entry with a barrier that is set

--      false by a protected procedure (which simulates starting a print job

--      on the printer), and is set true by a second protected procedure (which

--      simulates a handler called when the printer interrupts, indicating

--      that printing is done).

--

--      For the task, declare an entry whose corresponding accept statement

--      contains a call to first protected procedure of the protected type

--      (which sets the barrier of the protected entry to false), followed by

--      a requeue with abort to the protected entry. Declare a second entry

--      which does nothing.

--

--      Declare a "requesting" task which calls the printer server task entry

--      (and thus executes the requeue). Attempt to abort the requesting

--      task. Verify that it is aborted, that the requeued entry call is

--      canceled, and that the corresponding entry body is not executed.

--

-- TEST FILES:

--      This test depends on the following foundation code:

--

--         F954A00.A

--

--

--

-- CHANGE HISTORY:

--      06 Dec 94   SAIC    ACVC 2.0

--      10 Oct 96   SAIC    Added pragma elaborate

--

--!

package C954A02_0 is  -- Printer server abstraction.

   -- Simulate a system with multiple printers. The entry Print requests

   -- that data be printed on the next available printer. The entry call

   -- is accepted when a printer is available, and completes when printing

   -- is done.

   task Printer_Server is

      entry Print (File_Name : String);        -- Test the requeue statement.

      entry Verify_Results;                    -- Artifice for test purposes.

   end Printer_Server;

end C954A02_0;

     --==================================================================--

with Report;

with ImpDef;

with F954A00;              -- Printer device abstraction.

use  F954A00;

pragma Elaborate(F954a00);

package body C954A02_0 is  -- Printer server abstraction.

   task body Printer_Server is

      Printers_Busy  : Boolean    := True;

      Index          : Printer_ID := 1;

      Print_Accepted : Boolean    := False;

   begin

      loop

         -- Wait for a printer to become available:

         while Printers_Busy loop

            Printers_Busy := False;                        -- Exit loop if

                                                           -- entry accepted.

            select

               Printer(Index).Done_Printing;               -- Accepted immed.

                                                           -- when printer is

                                                           -- available.

            else

               Index := 1 + (Index mod Number_Of_Printers);-- Entry not immed.

               Printers_Busy := True;                      -- accepted; keep

            end select;                                    -- looping.

            -- Allow other task to get control

            delay ImpDef.Minimum_Task_Switch;

         end loop;                                         -- Value of Index

                                                           -- at loop exit

                                                           -- identifies the

                                                           -- avail. printer.

         -- Wait for a print request or terminate:

         select

            accept Print (File_Name : String) do

               Print_Accepted := True;                     -- Allow

                                                           -- Verify_Results

                                                           -- to be accepted.

               Printer(Index).Start_Printing (File_Name);  -- Begin printing on

                                                           -- the available

               --                        --                -- printer.

               -- Requeue is tested here --

               --                        --

                                                           -- Requeue caller so

               requeue Printer(Index).Done_Printing        -- server task free

                 with abort;                               -- to accept other

            end Print;                                     -- requests.

         or

            -- Guard ensures that Verify_Results cannot be accepted

            -- until after Print has been accepted. This avoids a

            -- race condition in the main program.

            when Print_Accepted => accept Verify_Results;  -- Artifice for

                                                           -- testing purposes.

         or

            terminate;

         end select;

      end loop;

   exception

      when others =>

         Report.Failed ("Exception raised in Printer_Server task");

   end Printer_Server;

end C954A02_0;

     --==================================================================--

with Report;

with ImpDef;

with F954A00;    -- Printer device abstraction.

with C954A02_0;  -- Printer server abstraction.

use  C954A02_0;

use  F954A00;

procedure C954A02 is

   -- Length of time which simulates a very long process

   Long_Enough : constant Duration := ImpDef.Clear_Ready_Queue;

               --==============================================--

   task Print_Request;                       -- Send a print request.

   task body Print_Request is

      My_File : constant String := "MYFILE.DAT";

   begin

      Printer_Server.Print (My_File);          -- Invoke requeue statement.

      Report.Failed ("Task continued execution following entry call");

   exception

      when others =>

         Report.Failed ("Exception raised in Print_Request task");

   end Print_Request;

               --==============================================--

begin  -- Main program.

   Report.Test ("C954A02", "Abort a requeue on a Protected entry");

   -- To pass this test, the following must be true:

   --

   --    (A) The abort of Print_Request takes place immediately.

   --    (B) The Done_Printing entry call is canceled, and the corresponding

   --        entry body is not executed.

   --

   -- Call the entry Verify_Results. The entry call will not be accepted

   -- until after Print_Request has been requeued to Done_Printing.

   Printer_Server.Verify_Results;           -- Accepted after Print_Request is

                                            -- requeued to Done_Printing.

   -- Verify that the Done_Printing entry call has not been completed.

   --

   if Printer(1).Is_Done then

      Report.Failed ("Target entry of requeue executed prematurely");

   else

      -- Simulate an application which needs access to the printer within

      -- a specified time, and which aborts the current printer job if time

      -- runs out.

      select

         Printer(1).Done_Printing;          -- Wait for printer to come free.

      or

         delay Long_Enough;                 -- Print job took too long.

         abort Print_Request;               -- Abort print job.

      end select;

      Printer_Server.Verify_Results;        -- Abortion completion point: force

                                            -- Print_Request abort to complete.

      -- Verify (A): that Print_Request has been aborted.

      -- Note: the test will hang if the task as not been aborted

      --

      while not Print_Request'Terminated loop

         delay ImpDef.Minimum_Task_Switch;

      end loop;

      -- Verify (B): that the Done_Printing entry call was canceled, and

      -- the corresponding entry body was not executed.

      --

      -- Set the barrier of the entry to true, then check that the entry

      -- body is not executed. If the entry call is NOT canceled, the

      -- entry body will execute when the barrier is set true.

      Printer(1).Handle_Interrupt;       -- Simulate a printer interrupt,

                                         -- signaling that printing is

                                         -- done.

      if Printer(1).Is_Done then

         Report.Failed ("Entry call was not canceled");

      end if;

   end if;

   Report.Result;

end C954A02;