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1 : // Support for atomic operations -*- C++ -*-
2 :
3 : // Copyright (C) 2004-2016 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 99241 : __exchange_and_add(volatile _Atomic_word* __mem, int __val)
49 99241 : { return __atomic_fetch_add(__mem, __val, __ATOMIC_ACQ_REL); }
50 :
51 : static inline void
52 62232 : __atomic_add(volatile _Atomic_word* __mem, int __val)
53 62232 : { __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 0 : __exchange_and_add_single(_Atomic_word* __mem, int __val)
66 : {
67 0 : _Atomic_word __result = *__mem;
68 0 : *__mem += __val;
69 0 : return __result;
70 : }
71 :
72 : static inline void
73 0 : __atomic_add_single(_Atomic_word* __mem, int __val)
74 0 : { *__mem += __val; }
75 :
76 : static inline _Atomic_word
77 : __attribute__ ((__unused__))
78 99241 : __exchange_and_add_dispatch(_Atomic_word* __mem, int __val)
79 : {
80 : #ifdef __GTHREADS
81 99241 : if (__gthread_active_p())
82 99241 : return __exchange_and_add(__mem, __val);
83 : else
84 0 : 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 62232 : __atomic_add_dispatch(_Atomic_word* __mem, int __val)
93 : {
94 : #ifdef __GTHREADS
95 62232 : if (__gthread_active_p())
96 62232 : __atomic_add(__mem, __val);
97 : else
98 0 : __atomic_add_single(__mem, __val);
99 : #else
100 : __atomic_add_single(__mem, __val);
101 : #endif
102 62232 : }
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
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