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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) 1991-2009, 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 a OpenVMS/Alpha 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;
with System.Aux_DEC;
 
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 in the
   --  Ada_Task_Control_Block.
 
   subtype Task_Address is System.Aux_DEC.Short_Address;
   --  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 := System.Aux_DEC.Short_Address_Size;
   --  The size of Task_Address
 
   Alternate_Stack_Size : constant := 0;
   --  No alternate signal stack is used on this platform
 
private
 
   type Exc_Stack_T is array (0 .. 8192) of aliased Character;
   for Exc_Stack_T'Alignment use Standard'Maximum_Alignment;
   type Exc_Stack_Ptr_T is access all Exc_Stack_T;
 
   type Lock is record
      L         : aliased System.OS_Interface.pthread_mutex_t;
      Prio      : Interfaces.C.int;
      Prio_Save : 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 ondition 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
 
      Exc_Stack_Ptr : Exc_Stack_Ptr_T;
      --  ??? This needs comments
 
      AST_Pending : Boolean;
      --  Used to detect delay and sleep timeouts
 
   end record;
 
end System.Task_Primitives;