atomicity.h revision 117397 
1// Low-level functions for atomic operations: x86, x >= 3 version  -*- C++ -*-
2
3// Copyright (C) 2003 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, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
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#ifndef _BITS_ATOMICITY_H
31#define _BITS_ATOMICITY_H	1
32
33typedef int _Atomic_word;
34
35template <int __inst>
36struct __Atomicity_lock
37{
38  static volatile _Atomic_word _S_atomicity_lock;
39};
40
41template <int __inst>
42volatile _Atomic_word __Atomicity_lock<__inst>::_S_atomicity_lock = 0;
43
44template volatile _Atomic_word __Atomicity_lock<0>::_S_atomicity_lock;
45
46static inline _Atomic_word
47__attribute__ ((__unused__))
48__exchange_and_add (volatile _Atomic_word *__mem, int __val)
49{
50  register _Atomic_word __result, __tmp = 1;
51
52  /* obtain the atomic exchange/add spin lock */
53  do {
54    __asm__ __volatile__ ("xchg{l} {%0,%1|%1,%0}"
55			  : "+m" (__Atomicity_lock<0>::_S_atomicity_lock),
56			    "+r" (__tmp));
57  } while (__tmp);
58
59  __result = *__mem;
60  *__mem += __val;
61
62  /* release spin lock */
63  __Atomicity_lock<0>::_S_atomicity_lock = 0;
64
65  return __result;
66}
67
68static inline void
69__attribute__ ((__unused__))
70__atomic_add (volatile _Atomic_word* __mem, int __val)
71{
72  __exchange_and_add (__mem, __val);
73}
74
75#endif /* atomicity.h */
76