------------------------------------------------------------------------------
--                                                                          --
--                 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) 1991-2017, Florida State University             --
--                     Copyright (C) 1995-2020, AdaCore                     --
--                                                                          --
-- GNAT 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 a POSIX-like version of this package

--  Note: this file can only be used for POSIX compliant systems

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 latter serves only as a semaphore so that
   --  we 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 in the
   --  Ada_Task_Control_Block.

   subtype Task_Address is System.Address;
   Task_Address_Size : constant := Standard'Address_Size;
   --  Type used for task addresses and its size

   Alternate_Stack_Size : constant := System.OS_Interface.Alternate_Stack_Size;
   --  Import value from System.OS_Interface

private

   type RTS_Lock is new System.OS_Interface.pthread_mutex_t;

   type Lock is record
      RW : aliased System.OS_Interface.pthread_rwlock_t;
      WO : aliased RTS_Lock;
   end record;

   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 RTS_Lock;
      --  Protection for ensuring mutual exclusion on the Suspension_Object

      CV : aliased System.OS_Interface.pthread_cond_t;
      --  Condition variable used to queue threads until condition is signaled
   end record;

   type Private_Data is limited 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.

      LWP : aliased System.Address;
      --  The purpose of this field is to provide a better tasking support on
      --  gdb. The order of the two first fields (Thread and LWP) is important.
      --  On targets where lwp is not relevant, this is equivalent to Thread.

      CV : aliased System.OS_Interface.pthread_cond_t;
      --  Should be commented ??? (in all versions of taspri)

      L : aliased RTS_Lock;
      --  Protection for all components is lock L
   end record;

end System.Task_Primitives;
