1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
|
------------------------------------------------------------------------------
-- --
-- GNAT RUN-TIME COMPONENTS --
-- --
-- S Y S T E M . A T O M I C _ P R I M I T I V E S --
-- --
-- S p e c --
-- --
-- Copyright (C) 2012-2022, Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 3, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. --
-- --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception, --
-- version 3.1, as published by the Free Software Foundation. --
-- --
-- You should have received a copy of the GNU General Public License and --
-- a copy of the GCC Runtime Library Exception along with this program; --
-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
-- <http://www.gnu.org/licenses/>. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
-- This package contains both atomic primitives defined from GCC built-in
-- functions and operations used by the compiler to generate the lock-free
-- implementation of protected objects.
with Interfaces.C;
package System.Atomic_Primitives is
pragma Pure;
type uint is mod 2 ** Long_Integer'Size;
type uint8 is mod 2**8
with Size => 8;
type uint16 is mod 2**16
with Size => 16;
type uint32 is mod 2**32
with Size => 32;
type uint64 is mod 2**64
with Size => 64;
Relaxed : constant := 0;
Consume : constant := 1;
Acquire : constant := 2;
Release : constant := 3;
Acq_Rel : constant := 4;
Seq_Cst : constant := 5;
Last : constant := 6;
subtype Mem_Model is Integer range Relaxed .. Last;
------------------------------------
-- GCC built-in atomic primitives --
------------------------------------
generic
type Atomic_Type is mod <>;
function Atomic_Load
(Ptr : Address;
Model : Mem_Model := Seq_Cst) return Atomic_Type;
pragma Import (Intrinsic, Atomic_Load, "__atomic_load_n");
function Atomic_Load_8 is new Atomic_Load (uint8);
function Atomic_Load_16 is new Atomic_Load (uint16);
function Atomic_Load_32 is new Atomic_Load (uint32);
function Atomic_Load_64 is new Atomic_Load (uint64);
generic
type Atomic_Type is mod <>;
function Atomic_Compare_Exchange
(Ptr : Address;
Expected : Address;
Desired : Atomic_Type;
Weak : Boolean := False;
Success_Model : Mem_Model := Seq_Cst;
Failure_Model : Mem_Model := Seq_Cst) return Boolean;
pragma Import
(Intrinsic, Atomic_Compare_Exchange, "__atomic_compare_exchange_n");
function Atomic_Compare_Exchange_8 is new Atomic_Compare_Exchange (uint8);
function Atomic_Compare_Exchange_16 is new Atomic_Compare_Exchange (uint16);
function Atomic_Compare_Exchange_32 is new Atomic_Compare_Exchange (uint32);
function Atomic_Compare_Exchange_64 is new Atomic_Compare_Exchange (uint64);
function Atomic_Test_And_Set
(Ptr : System.Address;
Model : Mem_Model := Seq_Cst) return Boolean;
pragma Import (Intrinsic, Atomic_Test_And_Set, "__atomic_test_and_set");
procedure Atomic_Clear
(Ptr : System.Address;
Model : Mem_Model := Seq_Cst);
pragma Import (Intrinsic, Atomic_Clear, "__atomic_clear");
function Atomic_Always_Lock_Free
(Size : Interfaces.C.size_t;
Ptr : System.Address := System.Null_Address) return Boolean;
pragma Import
(Intrinsic, Atomic_Always_Lock_Free, "__atomic_always_lock_free");
--------------------------
-- Lock-free operations --
--------------------------
-- The lock-free implementation uses two atomic instructions for the
-- expansion of protected operations:
-- * Lock_Free_Read atomically loads the value contained in Ptr (with the
-- Acquire synchronization mode).
-- * Lock_Free_Try_Write atomically tries to write the Desired value into
-- Ptr if Ptr contains the Expected value. It returns true if the value
-- in Ptr was changed, or False if it was not, in which case Expected is
-- updated to the unexpected value in Ptr. Note that it does nothing and
-- returns true if Desired and Expected are equal.
generic
type Atomic_Type is mod <>;
function Lock_Free_Read (Ptr : Address) return Atomic_Type;
function Lock_Free_Read_8 is new Lock_Free_Read (uint8);
function Lock_Free_Read_16 is new Lock_Free_Read (uint16);
function Lock_Free_Read_32 is new Lock_Free_Read (uint32);
function Lock_Free_Read_64 is new Lock_Free_Read (uint64);
generic
type Atomic_Type is mod <>;
function Lock_Free_Try_Write
(Ptr : Address;
Expected : in out Atomic_Type;
Desired : Atomic_Type) return Boolean;
function Lock_Free_Try_Write_8 is new Lock_Free_Try_Write (uint8);
function Lock_Free_Try_Write_16 is new Lock_Free_Try_Write (uint16);
function Lock_Free_Try_Write_32 is new Lock_Free_Try_Write (uint32);
function Lock_Free_Try_Write_64 is new Lock_Free_Try_Write (uint64);
private
pragma Inline (Lock_Free_Read);
pragma Inline (Lock_Free_Try_Write);
end System.Atomic_Primitives;
|
