1------------------------------------------------------------------------------
2--                                                                          --
3--                  GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                --
4--                                                                          --
5--                 S Y S T E M . T A S K _ P R I M I T I V E S              --
6--                                                                          --
7--                                  S p e c                                 --
8--                                                                          --
9--          Copyright (C) 2001-2011, Free Software Foundation, Inc.         --
10--                                                                          --
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.                                     --
17--                                                                          --
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.               --
21--                                                                          --
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/>.                                          --
26--                                                                          --
27-- GNARL was developed by the GNARL team at Florida State University.       --
28-- Extensive contributions were provided by Ada Core Technologies, Inc.     --
29--                                                                          --
30------------------------------------------------------------------------------
31
32--  This is a VxWorks version of this package
33
34pragma Polling (Off);
35--  Turn off polling, we do not want ATC polling to take place during tasking
36--  operations. It causes infinite loops and other problems.
37
38with System.OS_Interface;
39
40package System.Task_Primitives is
41   pragma Preelaborate;
42
43   type Lock is limited private;
44   --  Should be used for implementation of protected objects
45
46   type RTS_Lock is limited private;
47   --  Should be used inside the runtime system. The difference between Lock
48   --  and the RTS_Lock is that the later one serves only as a semaphore so
49   --  that do not check for ceiling violations.
50
51   type Suspension_Object is limited private;
52   --  Should be used for the implementation of Ada.Synchronous_Task_Control
53
54   type Task_Body_Access is access procedure;
55   --  Pointer to the task body's entry point (or possibly a wrapper
56   --  declared local to the GNARL).
57
58   type Private_Data is limited private;
59   --  Any information that the GNULLI needs maintained on a per-task basis.
60   --  A component of this type is guaranteed to be included in the
61   --  Ada_Task_Control_Block.
62
63   subtype Task_Address is System.Address;
64   --  In some versions of Task_Primitives, notably for VMS, Task_Address is
65   --  the short version of address defined in System.Aux_DEC. To avoid
66   --  dragging Aux_DEC into tasking packages a tasking specific subtype is
67   --  defined here.
68
69   Task_Address_Size : constant := Standard'Address_Size;
70   --  The size of Task_Address
71
72   Alternate_Stack_Size : constant := 0;
73   --  No alternate signal stack is used on this platform
74
75private
76
77   type Priority_Type is (Prio_None, Prio_Protect, Prio_Inherit);
78
79   type Lock is record
80      Mutex    : System.OS_Interface.SEM_ID;
81      Protocol : Priority_Type;
82
83      Prio_Ceiling : System.OS_Interface.int;
84      --  Priority ceiling of lock
85   end record;
86
87   type RTS_Lock is new Lock;
88
89   type Suspension_Object is record
90      State : Boolean;
91      pragma Atomic (State);
92      --  Boolean that indicates whether the object is open. This field is
93      --  marked Atomic to ensure that we can read its value without locking
94      --  the access to the Suspension_Object.
95
96      Waiting : Boolean;
97      --  Flag showing if there is a task already suspended on this object
98
99      L : aliased System.OS_Interface.SEM_ID;
100      --  Protection for ensuring mutual exclusion on the Suspension_Object
101
102      CV : aliased System.OS_Interface.SEM_ID;
103      --  Condition variable used to queue threads until condition is signaled
104   end record;
105
106   type Private_Data is record
107      Thread : aliased System.OS_Interface.t_id := 0;
108      pragma Atomic (Thread);
109      --  Thread field may be updated by two different threads of control.
110      --  (See, Enter_Task and Create_Task in s-taprop.adb).
111      --  They put the same value (thr_self value). We do not want to
112      --  use lock on those operations and the only thing we have to
113      --  make sure is that they are updated in atomic fashion.
114
115      LWP : aliased System.OS_Interface.t_id := 0;
116      --  The purpose of this field is to provide a better tasking support on
117      --  gdb. The order of the two first fields (Thread and LWP) is important.
118      --  On targets where lwp is not relevant, this is equivalent to Thread.
119
120      CV : aliased System.OS_Interface.SEM_ID;
121
122      L  : aliased RTS_Lock;
123      --  Protection for all components is lock L
124   end record;
125
126end System.Task_Primitives;
127