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------------------------------------------------------------------------------

--                                                                          --

--                 GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                 --

--                                                                          --

--                 S Y S T E M . T A S K _ P R I M I T I V E S              --

--                                                                          --

--                                  S p e c                                 --

--                                                                          --

--          Copyright (C) 1991-2011, Free Software Foundation, Inc.         --

--                                                                          --

-- GNARL is free software; you can  redistribute it  and/or modify it under --

-- terms of the  GNU General Public License as published  by the Free Soft- --

-- ware  Foundation;  either version 3,  or (at your option) any later ver- --

-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --

-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --

-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --

--                                                                          --

-- As a special exception under Section 7 of GPL version 3, you are granted --

-- additional permissions described in the GCC Runtime Library Exception,   --

-- version 3.1, as published by the Free Software Foundation.               --

--                                                                          --

-- You should have received a copy of the GNU General Public License and    --

-- a copy of the GCC Runtime Library Exception along with this program;     --

-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --

-- <http://www.gnu.org/licenses/>.                                          --

--                                                                          --

-- GNARL was developed by the GNARL team at Florida State University.       --

-- Extensive contributions were provided by Ada Core Technologies, Inc.     --

--                                                                          --

------------------------------------------------------------------------------

--  This is the DEC Unix 4.0 version of this package

--  This package provides low-level support for most tasking features

pragma Polling (Off);

--  Turn off polling, we do not want ATC polling to take place during tasking

--  operations. It causes infinite loops and other problems.

with Interfaces.C;

with System.OS_Interface;

package System.Task_Primitives is

   pragma Preelaborate;

   type Lock is limited private;

   --  Should be used for implementation of protected objects

   type RTS_Lock is limited private;

   --  Should be used inside the runtime system. The difference between Lock

   --  and the RTS_Lock is that the later one serves only as a semaphore so

   --  that do not check for ceiling violations.

   type Suspension_Object is limited private;

   --  Should be used for the implementation of Ada.Synchronous_Task_Control

   type Task_Body_Access is access procedure;

   --  Pointer to the task body's entry point (or possibly a wrapper

   --  declared local to the GNARL).

   type Private_Data is limited private;

   --  Any information that the GNULLI needs maintained on a per-task basis.

   --  A component of this type is guaranteed to be included

   subtype Task_Address is System.Address;

   --  In some versions of Task_Primitives, notably for VMS, Task_Address is

   --  the short version of address defined in System.Aux_DEC. To avoid

   --  dragging Aux_DEC into tasking packages a tasking specific subtype is

   --  defined here.

   Task_Address_Size : constant := Standard'Address_Size;

   --  The size of Task_Address

   Alternate_Stack_Size : constant := 0;

   --  No alternate signal stack is used on this platform

private

   type Lock is record

      L       : aliased System.OS_Interface.pthread_mutex_t;

      Ceiling : Interfaces.C.int;

   end record;

   type RTS_Lock is new System.OS_Interface.pthread_mutex_t;

   type Suspension_Object is record

      State : Boolean;

      pragma Atomic (State);

      --  Boolean that indicates whether the object is open. This field is

      --  marked Atomic to ensure that we can read its value without locking

      --  the access to the Suspension_Object.

      Waiting : Boolean;

      --  Flag showing if there is a task already suspended on this object

      L : aliased System.OS_Interface.pthread_mutex_t;

      --  Protection for ensuring mutual exclusion on the Suspension_Object

      CV : aliased System.OS_Interface.pthread_cond_t;

      --  Condition variable used to queue threads until the is signaled

   end record;

   type Private_Data is record

      Thread : aliased System.OS_Interface.pthread_t;

      pragma Atomic (Thread);

      --  Thread field may be updated by two different threads of control.

      --  (See, Enter_Task and Create_Task in s-taprop.adb). They put the same

      --  value (thr_self value). We do not want to use lock on those

      --  operations and the only thing we have to make sure is that they are

      --  updated in atomic fashion.

      CV : aliased System.OS_Interface.pthread_cond_t;

      L : aliased RTS_Lock;

      --  Protection for all components is lock L

   end record;

end System.Task_Primitives;