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#pragma GCC system_header
33
34#include <bits/c++config.h>
35#include <bits/gthr.h>
36#include <bits/atomic_word.h>
37
38namespace __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 __asm __volatile ("":::"memory")
112#endif
113#ifndef _GLIBCXX_WRITE_MEM_BARRIER
114#define _GLIBCXX_WRITE_MEM_BARRIER __asm __volatile ("":::"memory")
115#endif
116
117#endif
118