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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) 1992-2012, 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. --
-- --
------------------------------------------------------------------------------
with System.Task_Primitives.Operations;
with System.Tasking;
with System.Parameters;
with System.Soft_Links;
with Ada.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
Ada.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 & "terminated 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);
Error_Message : constant String := "Trying to set the priority of a ";
Yield_Needed : Boolean;
begin
if Target = Convert_Ids (Ada.Task_Identification.Null_Task_Id) then
raise Program_Error with Error_Message & "null task";
end if;
-- Setting the priority of an already-terminated task doesn't do
-- anything (see RM-D.5.1(7)). Note that Get_Priority is different in
-- this regard.
if Task_Identification.Is_Terminated (T) then
return;
end if;
SSL.Abort_Defer.all;
if Single_Lock then
STPO.Lock_RTS;
end if;
STPO.Write_Lock (Target);
Target.Common.Base_Priority := Priority;
if Target.Common.Call /= null
and then
Target.Common.Call.Acceptor_Prev_Priority /= Priority_Not_Boosted
then
-- Target is within a rendezvous, so ensure the correct priority
-- will be reset when finishing the rendezvous, and only change the
-- priority immediately if the new priority is greater than the
-- current (inherited) priority.
Target.Common.Call.Acceptor_Prev_Priority := Priority;
if Priority >= Target.Common.Current_Priority then
Yield_Needed := True;
STPO.Set_Priority (Target, Priority);
else
Yield_Needed := False;
end if;
else
Yield_Needed := True;
STPO.Set_Priority (Target, Priority);
if Target.Common.State = Entry_Caller_Sleep then
Target.Pending_Priority_Change := True;
STPO.Wakeup (Target, Target.Common.State);
end if;
end if;
STPO.Unlock (Target);
if Single_Lock then
STPO.Unlock_RTS;
end if;
if STPO.Self = Target and then Yield_Needed then
-- 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;
end if;
SSL.Abort_Undefer.all;
end Set_Priority;
end Ada.Dynamic_Priorities;
|
