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1 : : // Support for atomic operations -*- C++ -*-
2 : :
3 : : // Copyright (C) 2004, 2005, 2006 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 2, 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 : : // You should have received a copy of the GNU General Public License along
17 : : // with this library; see the file COPYING. If not, write to the Free
18 : : // Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
19 : : // USA.
20 : :
21 : : // As a special exception, you may use this file as part of a free software
22 : : // library without restriction. Specifically, if other files instantiate
23 : : // templates or use macros or inline functions from this file, or you compile
24 : : // this file and link it with other files to produce an executable, this
25 : : // file does not by itself cause the resulting executable to be covered by
26 : : // the GNU General Public License. This exception does not however
27 : : // invalidate any other reasons why the executable file might be covered by
28 : : // the GNU General Public License.
29 : :
30 : : /** @file atomicity.h
31 : : * This is an internal header file, included by other library headers.
32 : : * You should not attempt to use it directly.
33 : : */
34 : :
35 : : #ifndef _GLIBCXX_ATOMICITY_H
36 : : #define _GLIBCXX_ATOMICITY_H 1
37 : :
38 : : #include <bits/c++config.h>
39 : : #include <bits/gthr.h>
40 : : #include <bits/atomic_word.h>
41 : :
42 : : _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)
43 : :
44 : : // Functions for portable atomic access.
45 : : // To abstract locking primitives across all thread policies, use:
46 : : // __exchange_and_add_dispatch
47 : : // __atomic_add_dispatch
48 : : #ifdef _GLIBCXX_ATOMIC_BUILTINS
49 : : static inline _Atomic_word
50 : : __exchange_and_add(volatile _Atomic_word* __mem, int __val)
51 : : { return __sync_fetch_and_add(__mem, __val); }
52 : :
53 : : static inline void
54 : : __atomic_add(volatile _Atomic_word* __mem, int __val)
55 : : { __sync_fetch_and_add(__mem, __val); }
56 : : #else
57 : : _Atomic_word
58 : : __attribute__ ((__unused__))
59 : : __exchange_and_add(volatile _Atomic_word*, int);
60 : :
61 : : void
62 : : __attribute__ ((__unused__))
63 : : __atomic_add(volatile _Atomic_word*, int);
64 : : #endif
65 : :
66 : : static inline _Atomic_word
67 : : __exchange_and_add_single(_Atomic_word* __mem, int __val)
68 : : {
69 : 0 : _Atomic_word __result = *__mem;
70 : 0 : *__mem += __val;
71 : 0 : return __result;
72 : : }
73 : :
74 : : static inline void
75 : : __atomic_add_single(_Atomic_word* __mem, int __val)
76 : 0 : { *__mem += __val; }
77 : :
78 : : static inline _Atomic_word
79 : : __attribute__ ((__unused__))
80 : : __exchange_and_add_dispatch(_Atomic_word* __mem, int __val)
81 : : {
82 : : #ifdef __GTHREADS
83 [ + - ]: 565077 : if (__gthread_active_p())
84 : 565077 : return __exchange_and_add(__mem, __val);
85 : : else
86 : 0 : return __exchange_and_add_single(__mem, __val);
87 : : #else
88 : : return __exchange_and_add_single(__mem, __val);
89 : : #endif
90 : : }
91 : :
92 : : static inline void
93 : : __attribute__ ((__unused__))
94 : : __atomic_add_dispatch(_Atomic_word* __mem, int __val)
95 : : {
96 : : #ifdef __GTHREADS
97 [ + - ]: 708033 : if (__gthread_active_p())
98 : 708033 : __atomic_add(__mem, __val);
99 : : else
100 : : __atomic_add_single(__mem, __val);
101 : : #else
102 : : __atomic_add_single(__mem, __val);
103 : : #endif
104 : : }
105 : :
106 : : _GLIBCXX_END_NAMESPACE
107 : :
108 : : // Even if the CPU doesn't need a memory barrier, we need to ensure
109 : : // that the compiler doesn't reorder memory accesses across the
110 : : // barriers.
111 : : #ifndef _GLIBCXX_READ_MEM_BARRIER
112 : : #define _GLIBCXX_READ_MEM_BARRIER __asm __volatile ("":::"memory")
113 : : #endif
114 : : #ifndef _GLIBCXX_WRITE_MEM_BARRIER
115 : : #define _GLIBCXX_WRITE_MEM_BARRIER __asm __volatile ("":::"memory")
116 : : #endif
117 : :
118 : : #endif
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