1 | // Support for atomic operations -*- C++ -*- |
2 | |
3 | // Copyright (C) 2004-2017 Free Software Foundation, Inc. |
4 | // |
5 | // This file is part of the GNU ISO C++ Library. This library is free |
6 | // software; you can redistribute it and/or modify it under the |
7 | // terms of the GNU General Public License as published by the |
8 | // Free Software Foundation; either version 3, or (at your option) |
9 | // any later version. |
10 | |
11 | // This library is distributed in the hope that it will be useful, |
12 | // but WITHOUT ANY WARRANTY; without even the implied warranty of |
13 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
14 | // GNU General Public License for more details. |
15 | |
16 | // Under Section 7 of GPL version 3, you are granted additional |
17 | // permissions described in the GCC Runtime Library Exception, version |
18 | // 3.1, as published by the Free Software Foundation. |
19 | |
20 | // You should have received a copy of the GNU General Public License and |
21 | // a copy of the GCC Runtime Library Exception along with this program; |
22 | // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see |
23 | // <http://www.gnu.org/licenses/>. |
24 | |
25 | /** @file ext/atomicity.h |
26 | * This file is a GNU extension to the Standard C++ Library. |
27 | */ |
28 | |
29 | #ifndef _GLIBCXX_ATOMICITY_H |
30 | #define _GLIBCXX_ATOMICITY_H 1 |
31 | |
32 | #pragma GCC system_header |
33 | |
34 | #include <bits/c++config.h> |
35 | #include <bits/gthr.h> |
36 | #include <bits/atomic_word.h> |
37 | |
38 | namespace __gnu_cxx _GLIBCXX_VISIBILITY(default) |
39 | { |
40 | _GLIBCXX_BEGIN_NAMESPACE_VERSION |
41 | |
42 | // Functions for portable atomic access. |
43 | // To abstract locking primitives across all thread policies, use: |
44 | // __exchange_and_add_dispatch |
45 | // __atomic_add_dispatch |
46 | #ifdef _GLIBCXX_ATOMIC_BUILTINS |
47 | static inline _Atomic_word |
48 | __exchange_and_add(volatile _Atomic_word* __mem, int __val) |
49 | { return __atomic_fetch_add(__mem, __val, __ATOMIC_ACQ_REL); } |
50 | |
51 | static inline void |
52 | __atomic_add(volatile _Atomic_word* __mem, int __val) |
53 | { __atomic_fetch_add(__mem, __val, __ATOMIC_ACQ_REL); } |
54 | #else |
55 | _Atomic_word |
56 | __attribute__ ((__unused__)) |
57 | __exchange_and_add(volatile _Atomic_word*, int) throw (); |
58 | |
59 | void |
60 | __attribute__ ((__unused__)) |
61 | __atomic_add(volatile _Atomic_word*, int) throw (); |
62 | #endif |
63 | |
64 | static inline _Atomic_word |
65 | __exchange_and_add_single(_Atomic_word* __mem, int __val) |
66 | { |
67 | _Atomic_word __result = *__mem; |
68 | *__mem += __val; |
69 | return __result; |
70 | } |
71 | |
72 | static inline void |
73 | __atomic_add_single(_Atomic_word* __mem, int __val) |
74 | { *__mem += __val; } |
75 | |
76 | static inline _Atomic_word |
77 | __attribute__ ((__unused__)) |
78 | __exchange_and_add_dispatch(_Atomic_word* __mem, int __val) |
79 | { |
80 | #ifdef __GTHREADS |
81 | if (__gthread_active_p()) |
82 | return __exchange_and_add(__mem, __val); |
83 | else |
84 | return __exchange_and_add_single(__mem, __val); |
85 | #else |
86 | return __exchange_and_add_single(__mem, __val); |
87 | #endif |
88 | } |
89 | |
90 | static inline void |
91 | __attribute__ ((__unused__)) |
92 | __atomic_add_dispatch(_Atomic_word* __mem, int __val) |
93 | { |
94 | #ifdef __GTHREADS |
95 | if (__gthread_active_p()) |
96 | __atomic_add(__mem, __val); |
97 | else |
98 | __atomic_add_single(__mem, __val); |
99 | #else |
100 | __atomic_add_single(__mem, __val); |
101 | #endif |
102 | } |
103 | |
104 | _GLIBCXX_END_NAMESPACE_VERSION |
105 | } // namespace |
106 | |
107 | // Even if the CPU doesn't need a memory barrier, we need to ensure |
108 | // that the compiler doesn't reorder memory accesses across the |
109 | // barriers. |
110 | #ifndef _GLIBCXX_READ_MEM_BARRIER |
111 | #define _GLIBCXX_READ_MEM_BARRIER __atomic_thread_fence (__ATOMIC_ACQUIRE) |
112 | #endif |
113 | #ifndef _GLIBCXX_WRITE_MEM_BARRIER |
114 | #define _GLIBCXX_WRITE_MEM_BARRIER __atomic_thread_fence (__ATOMIC_RELEASE) |
115 | #endif |
116 | |
117 | #endif |
118 | |