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

--                                                                          --

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

--                                                                          --

--                 A D A . D Y N A M I C _ P R I O R I T I E S              --

--                                                                          --

--                                  B o d y                                 --

--                                                                          --

--          Copyright (C) 1992-2005, 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.     --

--                                                                          --

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

with Ada.Task_Identification;

--  used for Task_Id

--           Current_Task

--           Null_Task_Id

--           Is_Terminated

with System.Task_Primitives.Operations;

--  used for Write_Lock

--           Unlock

--           Set_Priority

--           Wakeup

--           Self

with System.Tasking;

--  used for Task_Id

with System.Parameters;

--  used for Single_Lock

with System.Soft_Links;

--  use for Abort_Defer

--          Abort_Undefer

with Unchecked_Conversion;

package body Ada.Dynamic_Priorities is

   package STPO renames System.Task_Primitives.Operations;

   package SSL renames System.Soft_Links;

   use System.Parameters;

   use System.Tasking;

   function Convert_Ids is new

     Unchecked_Conversion

       (Task_Identification.Task_Id, System.Tasking.Task_Id);

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

   -- Get_Priority --

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

   --  Inquire base priority of a task

   function Get_Priority

     (T : Ada.Task_Identification.Task_Id :=

        Ada.Task_Identification.Current_Task) return System.Any_Priority

   is

      Target : constant Task_Id := Convert_Ids (T);

      Error_Message : constant String := "Trying to get the priority of a ";

   begin

      if Target = Convert_Ids (Ada.Task_Identification.Null_Task_Id) then

         raise Program_Error with Error_Message & "null task";

      end if;

      if Task_Identification.Is_Terminated (T) then

         raise Tasking_Error with Error_Message & "null task";

      end if;

      return Target.Common.Base_Priority;

   end Get_Priority;

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

   -- Set_Priority --

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

   --  Change base priority of a task dynamically

   procedure Set_Priority

     (Priority : System.Any_Priority;

      T        : Ada.Task_Identification.Task_Id :=

                   Ada.Task_Identification.Current_Task)

   is

      Target  : constant Task_Id := Convert_Ids (T);

      Self_ID : constant Task_Id := STPO.Self;

      Error_Message : constant String := "Trying to set the priority of a ";

   begin

      if Target = Convert_Ids (Ada.Task_Identification.Null_Task_Id) then

         raise Program_Error with Error_Message & "null task";

      end if;

      if Task_Identification.Is_Terminated (T) then

         raise Tasking_Error with Error_Message & "terminated task";

      end if;

      SSL.Abort_Defer.all;

      if Single_Lock then

         STPO.Lock_RTS;

      end if;

      STPO.Write_Lock (Target);

      if Self_ID = Target then

         Target.Common.Base_Priority := Priority;

         STPO.Set_Priority (Target, Priority);

         STPO.Unlock (Target);

         if Single_Lock then

            STPO.Unlock_RTS;

         end if;

         --  Yield is needed to enforce FIFO task dispatching

         --  LL Set_Priority is made while holding the RTS lock so that it

         --  is inheriting high priority until it release all the RTS locks.

         --  If this is used in a system where Ceiling Locking is

         --  not enforced we may end up getting two Yield effects.

         STPO.Yield;

      else

         Target.New_Base_Priority := Priority;

         Target.Pending_Priority_Change := True;

         Target.Pending_Action := True;

         STPO.Wakeup (Target, Target.Common.State);

         --  If the task is suspended, wake it up to perform the change.

         --  check for ceiling violations ???

         STPO.Unlock (Target);

         if Single_Lock then

            STPO.Unlock_RTS;

         end if;

      end if;

      SSL.Abort_Undefer.all;

   end Set_Priority;

end Ada.Dynamic_Priorities;