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) 1991-2017, Florida State University             --
10--                     Copyright (C) 1995-2019, 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 latter serves only as a semaphore so that
52   --  we 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   Task_Address_Size : constant := Standard'Address_Size;
68   --  Type used for task addresses and its size
69
70   Alternate_Stack_Size : constant := System.OS_Interface.Alternate_Stack_Size;
71   --  Import value from System.OS_Interface
72
73private
74
75   type RTS_Lock is new System.OS_Interface.pthread_mutex_t;
76
77   type Lock is record
78      RW : aliased System.OS_Interface.pthread_rwlock_t;
79      WO : aliased RTS_Lock;
80   end record;
81
82   type Suspension_Object is record
83      State : Boolean;
84      pragma Atomic (State);
85      --  Boolean that indicates whether the object is open. This field is
86      --  marked Atomic to ensure that we can read its value without locking
87      --  the access to the Suspension_Object.
88
89      Waiting : Boolean;
90      --  Flag showing if there is a task already suspended on this object
91
92      L : aliased RTS_Lock;
93      --  Protection for ensuring mutual exclusion on the Suspension_Object
94
95      CV : aliased System.OS_Interface.pthread_cond_t;
96      --  Condition variable used to queue threads until condition is signaled
97   end record;
98
99   type Private_Data is limited record
100      Thread : aliased System.OS_Interface.pthread_t;
101      pragma Atomic (Thread);
102      --  Thread field may be updated by two different threads of control.
103      --  (See, Enter_Task and Create_Task in s-taprop.adb). They put the same
104      --  value (thr_self value). We do not want to use lock on those
105      --  operations and the only thing we have to make sure is that they are
106      --  updated in atomic fashion.
107
108      LWP : aliased System.Address;
109      --  The purpose of this field is to provide a better tasking support on
110      --  gdb. The order of the two first fields (Thread and LWP) is important.
111      --  On targets where lwp is not relevant, this is equivalent to Thread.
112
113      CV : aliased System.OS_Interface.pthread_cond_t;
114      --  Should be commented ??? (in all versions of taspri)
115
116      L : aliased RTS_Lock;
117      --  Protection for all components is lock L
118   end record;
119
120end System.Task_Primitives;
121