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    _Atomic_word __result = *__mem;
70    *__mem += __val;
71    return __result;
72  }
73
74  static inline void
75  __atomic_add_single(_Atomic_word* __mem, int __val)
76  { *__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    if (__gthread_active_p())
84      return __exchange_and_add(__mem, __val);
85    else
86      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    if (__gthread_active_p())
98      __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
119