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 where no alternate stack
34--  is needed for stack checking.
35
36--  Note: this file can only be used for POSIX compliant systems
37
38pragma Polling (Off);
39--  Turn off polling, we do not want ATC polling to take place during tasking
40--  operations. It causes infinite loops and other problems.
41
42with System.OS_Interface;
43
44package System.Task_Primitives is
45   pragma Preelaborate;
46
47   type Lock is limited private;
48   --  Should be used for implementation of protected objects
49
50   type RTS_Lock is limited private;
51   --  Should be used inside the runtime system. The difference between Lock
52   --  and the RTS_Lock is that the later one serves only as a semaphore so
53   --  that do not check for ceiling violations.
54
55   type Suspension_Object is limited private;
56   --  Should be used for the implementation of Ada.Synchronous_Task_Control
57
58   type Task_Body_Access is access procedure;
59   --  Pointer to the task body's entry point (or possibly a wrapper declared
60   --  local to the GNARL).
61
62   type Private_Data is limited private;
63   --  Any information that the GNULLI needs maintained on a per-task basis.
64   --  A component of this type is guaranteed to be included in the
65   --  Ada_Task_Control_Block.
66
67   subtype Task_Address is System.Address;
68   --  In some versions of Task_Primitives, notably for VMS, Task_Address is
69   --  the short version of address defined in System.Aux_DEC. To avoid
70   --  dragging Aux_DEC into tasking packages a tasking specific subtype is
71   --  defined here.
72
73   Task_Address_Size : constant := Standard'Address_Size;
74   --  The size of Task_Address
75
76   Alternate_Stack_Size : constant := 0;
77   --  No alternate signal stack is used on this platform
78
79private
80
81   type Lock is record
82      WO : aliased System.OS_Interface.pthread_mutex_t;
83      RW : aliased System.OS_Interface.pthread_rwlock_t;
84   end record;
85
86   type RTS_Lock is new System.OS_Interface.pthread_mutex_t;
87
88   type Suspension_Object is record
89      State : Boolean;
90      pragma Atomic (State);
91      --  Boolean that indicates whether the object is open. This field is
92      --  marked Atomic to ensure that we can read its value without locking
93      --  the access to the Suspension_Object.
94
95      Waiting : Boolean;
96      --  Flag showing if there is a task already suspended on this object
97
98      L : aliased System.OS_Interface.pthread_mutex_t;
99      --  Protection for ensuring mutual exclusion on the Suspension_Object
100
101      CV : aliased System.OS_Interface.pthread_cond_t;
102      --  Condition variable used to queue threads until condition is signaled
103   end record;
104
105   type Private_Data is record
106      Thread : aliased System.OS_Interface.pthread_t;
107      pragma Atomic (Thread);
108      --  Thread field may be updated by two different threads of control.
109      --  (See, Enter_Task and Create_Task in s-taprop.adb). They put the same
110      --  value (thr_self value). We do not want to use lock on those
111      --  operations and the only thing we have to make sure is that they are
112      --  updated in atomic fashion.
113
114      LWP : aliased System.Address;
115      --  The purpose of this field is to provide a better tasking support on
116      --  gdb. The order of the two first fields (Thread and LWP) is important.
117      --  On targets where lwp is not relevant, this is equivalent to Thread.
118
119      CV : aliased System.OS_Interface.pthread_cond_t;
120      --  Should be commented ??? (in all versions of taspri)
121
122      L : aliased RTS_Lock;
123      --  Protection for all components is lock L
124   end record;
125
126end System.Task_Primitives;
127