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) 1992-2017, 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 3, or (at your option) any later ver- --
14 -- sion. GNAT 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. --
18 -- As a special exception under Section 7 of GPL version 3, you are granted --
19 -- additional permissions described in the GCC Runtime Library Exception, --
20 -- version 3.1, as published by the Free Software Foundation. --
22 -- You should have received a copy of the GNU General Public License and --
23 -- a copy of the GCC Runtime Library Exception along with this program; --
24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
25 -- <http://www.gnu.org/licenses/>. --
27 -- GNARL was developed by the GNARL team at Florida State University. --
28 -- Extensive contributions were provided by Ada Core Technologies, Inc. --
30 ------------------------------------------------------------------------------
32 with System
.Task_Primitives
.Operations
;
34 with System
.Parameters
;
35 with System
.Soft_Links
;
37 with Ada
.Unchecked_Conversion
;
39 package body Ada
.Dynamic_Priorities
is
41 package STPO
renames System
.Task_Primitives
.Operations
;
42 package SSL
renames System
.Soft_Links
;
44 use System
.Parameters
;
47 function Convert_Ids
is new
48 Ada
.Unchecked_Conversion
49 (Task_Identification
.Task_Id
, System
.Tasking
.Task_Id
);
55 -- Inquire base priority of a task
58 (T
: Ada
.Task_Identification
.Task_Id
:=
59 Ada
.Task_Identification
.Current_Task
) return System
.Any_Priority
61 Target
: constant Task_Id
:= Convert_Ids
(T
);
62 Error_Message
: constant String := "Trying to get the priority of a ";
65 if Target
= Convert_Ids
(Ada
.Task_Identification
.Null_Task_Id
) then
66 raise Program_Error
with Error_Message
& "null task";
69 if Task_Identification
.Is_Terminated
(T
) then
70 raise Tasking_Error
with Error_Message
& "terminated task";
73 return Target
.Common
.Base_Priority
;
80 -- Change base priority of a task dynamically
82 procedure Set_Priority
83 (Priority
: System
.Any_Priority
;
84 T
: Ada
.Task_Identification
.Task_Id
:=
85 Ada
.Task_Identification
.Current_Task
)
87 Target
: constant Task_Id
:= Convert_Ids
(T
);
88 Error_Message
: constant String := "Trying to set the priority of a ";
89 Yield_Needed
: Boolean;
92 if Target
= Convert_Ids
(Ada
.Task_Identification
.Null_Task_Id
) then
93 raise Program_Error
with Error_Message
& "null task";
96 -- Setting the priority of an already-terminated task doesn't do
97 -- anything (see RM-D.5.1(7)). Note that Get_Priority is different in
100 if Task_Identification
.Is_Terminated
(T
) then
110 STPO
.Write_Lock
(Target
);
112 Target
.Common
.Base_Priority
:= Priority
;
114 if Target
.Common
.Call
/= null
116 Target
.Common
.Call
.Acceptor_Prev_Priority
/= Priority_Not_Boosted
118 -- Target is within a rendezvous, so ensure the correct priority
119 -- will be reset when finishing the rendezvous, and only change the
120 -- priority immediately if the new priority is greater than the
121 -- current (inherited) priority.
123 Target
.Common
.Call
.Acceptor_Prev_Priority
:= Priority
;
125 if Priority
>= Target
.Common
.Current_Priority
then
126 Yield_Needed
:= True;
127 STPO
.Set_Priority
(Target
, Priority
);
129 Yield_Needed
:= False;
133 Yield_Needed
:= True;
134 STPO
.Set_Priority
(Target
, Priority
);
136 if Target
.Common
.State
= Entry_Caller_Sleep
then
137 Target
.Pending_Priority_Change
:= True;
138 STPO
.Wakeup
(Target
, Target
.Common
.State
);
142 STPO
.Unlock
(Target
);
148 if STPO
.Self
= Target
and then Yield_Needed
then
150 -- Yield is needed to enforce FIFO task dispatching
152 -- LL Set_Priority is made while holding the RTS lock so that it is
153 -- inheriting high priority until it release all the RTS locks.
155 -- If this is used in a system where Ceiling Locking is not enforced
156 -- we may end up getting two Yield effects.
161 SSL
.Abort_Undefer
.all;
164 end Ada
.Dynamic_Priorities
;