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) 1991-1994, Florida State University             --
10--                     Copyright (C) 1995-2011, AdaCore                     --
11--                                                                          --
12-- GNAT is free software;  you can  redistribute it  and/or modify it under --
13-- terms of the  GNU General Public License as published  by the Free Soft- --
14-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
15-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
16-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
17-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
18--                                                                          --
19-- As a special exception under Section 7 of GPL version 3, you are granted --
20-- additional permissions described in the GCC Runtime Library Exception,   --
21-- version 3.1, as published by the Free Software Foundation.               --
22--                                                                          --
23-- You should have received a copy of the GNU General Public License and    --
24-- a copy of the GCC Runtime Library Exception along with this program;     --
25-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
26-- <http://www.gnu.org/licenses/>.                                          --
27--                                                                          --
28-- GNARL was developed by the GNARL team at Florida State University.       --
29-- Extensive contributions were provided by Ada Core Technologies, Inc.     --
30--                                                                          --
31------------------------------------------------------------------------------
32
33--  This is a POSIX-like version of this package
34
35--  Note: this file can only be used for POSIX compliant systems
36
37pragma Polling (Off);
38--  Turn off polling, we do not want ATC polling to take place during tasking
39--  operations. It causes infinite loops and other problems.
40
41with System.OS_Interface;
42
43package System.Task_Primitives is
44   pragma Preelaborate;
45
46   type Lock is limited private;
47   --  Should be used for implementation of protected objects
48
49   type RTS_Lock is limited private;
50   --  Should be used inside the runtime system. The difference between Lock
51   --  and the RTS_Lock is that the later one serves only as a semaphore so
52   --  that do not check for ceiling violations.
53
54   type Suspension_Object is limited private;
55   --  Should be used for the implementation of Ada.Synchronous_Task_Control
56
57   type Task_Body_Access is access procedure;
58   --  Pointer to the task body's entry point (or possibly a wrapper declared
59   --  local to the GNARL).
60
61   type Private_Data is limited private;
62   --  Any information that the GNULLI needs maintained on a per-task basis.
63   --  A component of this type is guaranteed to be included in the
64   --  Ada_Task_Control_Block.
65
66   subtype Task_Address is System.Address;
67   --  In some versions of Task_Primitives, notably for VMS, Task_Address is
68   --  the short version of address defined in System.Aux_DEC. To avoid
69   --  dragging Aux_DEC into tasking packages a tasking specific subtype is
70   --  defined here.
71
72   Task_Address_Size : constant := Standard'Address_Size;
73   --  The size of Task_Address
74
75   Alternate_Stack_Size : constant := System.OS_Interface.Alternate_Stack_Size;
76   --  Import value from System.OS_Interface
77
78private
79
80   type Lock is record
81      RW : aliased System.OS_Interface.pthread_rwlock_t;
82      WO : aliased System.OS_Interface.pthread_mutex_t;
83   end record;
84
85   type RTS_Lock is new System.OS_Interface.pthread_mutex_t;
86
87   type Suspension_Object is record
88      State : Boolean;
89      pragma Atomic (State);
90      --  Boolean that indicates whether the object is open. This field is
91      --  marked Atomic to ensure that we can read its value without locking
92      --  the access to the Suspension_Object.
93
94      Waiting : Boolean;
95      --  Flag showing if there is a task already suspended on this object
96
97      L : aliased System.OS_Interface.pthread_mutex_t;
98      --  Protection for ensuring mutual exclusion on the Suspension_Object
99
100      CV : aliased System.OS_Interface.pthread_cond_t;
101      --  Condition variable used to queue threads until condition is signaled
102   end record;
103
104   type Private_Data is record
105      Thread : aliased System.OS_Interface.pthread_t;
106      pragma Atomic (Thread);
107      --  Thread field may be updated by two different threads of control.
108      --  (See, Enter_Task and Create_Task in s-taprop.adb). They put the same
109      --  value (thr_self value). We do not want to use lock on those
110      --  operations and the only thing we have to make sure is that they are
111      --  updated in atomic fashion.
112
113      LWP : aliased System.Address;
114      --  The purpose of this field is to provide a better tasking support on
115      --  gdb. The order of the two first fields (Thread and LWP) is important.
116      --  On targets where lwp is not relevant, this is equivalent to Thread.
117
118      CV : aliased System.OS_Interface.pthread_cond_t;
119      --  Should be commented ??? (in all versions of taspri)
120
121      L : aliased RTS_Lock;
122      --  Protection for all components is lock L
123   end record;
124
125end System.Task_Primitives;
126