1 // Low-level functions for atomic operations: Generic version -*- C++ -*-
2
3 // Copyright (C) 1999-2020 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 #include <ext/atomicity.h>
26 #include <ext/concurrence.h>
27
28 namespace
29 {
30 __gnu_cxx::__mutex&
get_atomic_mutex()31 get_atomic_mutex()
32 {
33 static __gnu_cxx::__mutex atomic_mutex;
34 return atomic_mutex;
35 }
36 } // anonymous namespace
37
_GLIBCXX_VISIBILITY(default)38 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
39 {
40 _GLIBCXX_BEGIN_NAMESPACE_VERSION
41
42 _Atomic_word
43 __attribute__ ((__unused__))
44 __exchange_and_add(volatile _Atomic_word* __mem, int __val) throw ()
45 {
46 __gnu_cxx::__scoped_lock sentry(get_atomic_mutex());
47 _Atomic_word __result;
48 __result = *__mem;
49 *__mem += __val;
50 return __result;
51 }
52
53 void
54 __attribute__ ((__unused__))
55 __atomic_add(volatile _Atomic_word* __mem, int __val) throw ()
56 { __exchange_and_add(__mem, __val); }
57
58 _GLIBCXX_END_NAMESPACE_VERSION
59 } // namespace
60