libstdc++

atomicity.h
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1 // Support for atomic operations -*- C++ -*-
2
3 // Copyright (C) 2004-2013 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 #include <bits/c++config.h>
33 #include <bits/gthr.h>
34 #include <bits/atomic_word.h>
35
36 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
37 {
38 _GLIBCXX_BEGIN_NAMESPACE_VERSION
39
40 // Functions for portable atomic access.
41 // To abstract locking primitives across all thread policies, use:
42 // __exchange_and_add_dispatch
43 // __atomic_add_dispatch
44 #ifdef _GLIBCXX_ATOMIC_BUILTINS
45 static inline _Atomic_word
46 __exchange_and_add(volatile _Atomic_word* __mem, int __val)
47 { return __atomic_fetch_add(__mem, __val, __ATOMIC_ACQ_REL); }
48
49 static inline void
50 __atomic_add(volatile _Atomic_word* __mem, int __val)
51 { __atomic_fetch_add(__mem, __val, __ATOMIC_ACQ_REL); }
52 #else
53 _Atomic_word
54 __attribute__ ((__unused__))
55 __exchange_and_add(volatile _Atomic_word*, int) throw ();
56
57 void
58 __attribute__ ((__unused__))
59 __atomic_add(volatile _Atomic_word*, int) throw ();
60 #endif
61
62 static inline _Atomic_word
63 __exchange_and_add_single(_Atomic_word* __mem, int __val)
64 {
65 _Atomic_word __result = *__mem;
66 *__mem += __val;
67 return __result;
68 }
69
70 static inline void
71 __atomic_add_single(_Atomic_word* __mem, int __val)
72 { *__mem += __val; }
73
74 static inline _Atomic_word
75 __attribute__ ((__unused__))
76 __exchange_and_add_dispatch(_Atomic_word* __mem, int __val)
77 {
78 #ifdef __GTHREADS
79 if (__gthread_active_p())
80 return __exchange_and_add(__mem, __val);
81 else
82 return __exchange_and_add_single(__mem, __val);
83 #else
84 return __exchange_and_add_single(__mem, __val);
85 #endif
86 }
87
88 static inline void
89 __attribute__ ((__unused__))
90 __atomic_add_dispatch(_Atomic_word* __mem, int __val)
91 {
92 #ifdef __GTHREADS
93 if (__gthread_active_p())
94 __atomic_add(__mem, __val);
95 else
96 __atomic_add_single(__mem, __val);
97 #else
98 __atomic_add_single(__mem, __val);
99 #endif
100 }
101
102 _GLIBCXX_END_NAMESPACE_VERSION
103 } // namespace
104
105 // Even if the CPU doesn't need a memory barrier, we need to ensure
106 // that the compiler doesn't reorder memory accesses across the
107 // barriers.
108 #ifndef _GLIBCXX_READ_MEM_BARRIER
109 #define _GLIBCXX_READ_MEM_BARRIER __asm __volatile ("":::"memory")
110 #endif
111 #ifndef _GLIBCXX_WRITE_MEM_BARRIER
112 #define _GLIBCXX_WRITE_MEM_BARRIER __asm __volatile ("":::"memory")
113 #endif
114
115 #endif