------------------------------------------------------------------------------
--                                                                          --
--                 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) 1991-2005 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 2,  or (at your option) any later ver- --
-- sion. GNARL 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.  See the GNU General Public License --
-- for  more details.  You should have  received  a copy of the GNU General --
-- Public License  distributed with GNARL; see file COPYING.  If not, write --
-- to  the  Free Software Foundation,  51  Franklin  Street,  Fifth  Floor, --
-- Boston, MA 02110-1301, USA.                                              --
--                                                                          --
-- As a special exception,  if other files  instantiate  generics from this --
-- unit, or you link  this unit with other files  to produce an executable, --
-- this  unit  does not  by itself cause  the resulting  executable  to  be --
-- covered  by the  GNU  General  Public  License.  This exception does not --
-- however invalidate  any other reasons why  the executable file  might be --
-- covered by the  GNU Public License.                                      --
--                                                                          --
-- 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;
--  used for int
--           size_t

with System.OS_Interface;
--  used for pthread_mutex_t
--           pthread_cond_t
--           pthread_t

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

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;