1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS --
5 -- A D A . D Y N A M I C _ P R I O R I T I E S --
9 -- Copyright (C) 1992-2008, Free Software Foundation, Inc. --
11 -- GNARL is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 2, or (at your option) any later ver- --
14 -- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNARL; see file COPYING. If not, write --
19 -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
20 -- Boston, MA 02110-1301, USA. --
22 -- As a special exception, if other files instantiate generics from this --
23 -- unit, or you link this unit with other files to produce an executable, --
24 -- this unit does not by itself cause the resulting executable to be --
25 -- covered by the GNU General Public License. This exception does not --
26 -- however invalidate any other reasons why the executable file might be --
27 -- covered by the GNU Public License. --
29 -- GNARL was developed by the GNARL team at Florida State University. --
30 -- Extensive contributions were provided by Ada Core Technologies, Inc. --
32 ------------------------------------------------------------------------------
34 with System.Task_Primitives.Operations;
36 with System.Parameters;
37 with System.Soft_Links;
39 with Ada.Unchecked_Conversion;
41 package body Ada.Dynamic_Priorities is
43 package STPO renames System.Task_Primitives.Operations;
44 package SSL renames System.Soft_Links;
46 use System.Parameters;
49 function Convert_Ids is new
50 Ada.Unchecked_Conversion
51 (Task_Identification.Task_Id, System.Tasking.Task_Id);
57 -- Inquire base priority of a task
60 (T : Ada.Task_Identification.Task_Id :=
61 Ada.Task_Identification.Current_Task) return System.Any_Priority
63 Target : constant Task_Id := Convert_Ids (T);
64 Error_Message : constant String := "Trying to get the priority of a ";
67 if Target = Convert_Ids (Ada.Task_Identification.Null_Task_Id) then
68 raise Program_Error with Error_Message & "null task";
71 if Task_Identification.Is_Terminated (T) then
72 raise Tasking_Error with Error_Message & "null task";
75 return Target.Common.Base_Priority;
82 -- Change base priority of a task dynamically
84 procedure Set_Priority
85 (Priority : System.Any_Priority;
86 T : Ada.Task_Identification.Task_Id :=
87 Ada.Task_Identification.Current_Task)
89 Target : constant Task_Id := Convert_Ids (T);
90 Error_Message : constant String := "Trying to set the priority of a ";
91 Yield_Needed : Boolean;
94 if Target = Convert_Ids (Ada.Task_Identification.Null_Task_Id) then
95 raise Program_Error with Error_Message & "null task";
98 if Task_Identification.Is_Terminated (T) then
99 raise Tasking_Error with Error_Message & "terminated task";
108 STPO.Write_Lock (Target);
110 Target.Common.Base_Priority := Priority;
112 if Target.Common.Call /= null
114 Target.Common.Call.Acceptor_Prev_Priority /= Priority_Not_Boosted
116 -- Target is within a rendezvous, so ensure the correct priority
117 -- will be reset when finishing the rendezvous, and only change the
118 -- priority immediately if the new priority is greater than the
119 -- current (inherited) priority.
121 Target.Common.Call.Acceptor_Prev_Priority := Priority;
123 if Priority >= Target.Common.Current_Priority then
124 Yield_Needed := True;
125 STPO.Set_Priority (Target, Priority);
127 Yield_Needed := False;
131 Yield_Needed := True;
132 STPO.Set_Priority (Target, Priority);
134 if Target.Common.State = Entry_Caller_Sleep then
135 Target.Pending_Priority_Change := True;
136 STPO.Wakeup (Target, Target.Common.State);
140 STPO.Unlock (Target);
146 if STPO.Self = Target and then Yield_Needed then
148 -- Yield is needed to enforce FIFO task dispatching
150 -- LL Set_Priority is made while holding the RTS lock so that it is
151 -- inheriting high priority until it release all the RTS locks.
153 -- If this is used in a system where Ceiling Locking is not enforced
154 -- we may end up getting two Yield effects.
159 SSL.Abort_Undefer.all;
162 end Ada.Dynamic_Priorities;