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1 | // (C) Copyright 2013 Andrey Semashev |
2 | // (C) Copyright 2013 Vicente J. Botet Escriba | |
3 | // | |
4 | // Distributed under the Boost Software License, Version 1.0. (See accompanying | |
5 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
6 | ||
7 | //#define __STDC_CONSTANT_MACROS | |
8 | #include <boost/thread/detail/config.hpp> | |
9 | #include <boost/thread/once.hpp> | |
10 | #include <boost/thread/pthread/pthread_mutex_scoped_lock.hpp> | |
11 | #include <boost/assert.hpp> | |
12 | #include <boost/static_assert.hpp> | |
13 | #include <boost/atomic.hpp> | |
14 | #include <boost/memory_order.hpp> | |
15 | #include <pthread.h> | |
16 | ||
17 | namespace boost | |
18 | { | |
19 | namespace thread_detail | |
20 | { | |
21 | ||
22 | enum flag_states | |
23 | { | |
24 | uninitialized, in_progress, initialized | |
25 | }; | |
26 | ||
27 | ||
28 | #ifndef BOOST_THREAD_PROVIDES_ONCE_CXX11 | |
29 | BOOST_STATIC_ASSERT_MSG(sizeof(atomic_int_type) == sizeof(atomic_type), "Boost.Thread: unsupported platform"); | |
30 | #endif | |
31 | ||
32 | static pthread_mutex_t once_mutex = PTHREAD_MUTEX_INITIALIZER; | |
33 | static pthread_cond_t once_cv = PTHREAD_COND_INITIALIZER; | |
34 | ||
35 | BOOST_THREAD_DECL bool enter_once_region(once_flag& flag) BOOST_NOEXCEPT | |
36 | { | |
37 | atomic_type& f = get_atomic_storage(flag); | |
38 | if (f.load(memory_order_acquire) != initialized) | |
39 | { | |
40 | pthread::pthread_mutex_scoped_lock lk(&once_mutex); | |
41 | if (f.load(memory_order_acquire) != initialized) | |
42 | { | |
43 | while (true) | |
44 | { | |
45 | atomic_int_type expected = uninitialized; | |
46 | if (f.compare_exchange_strong(expected, in_progress, memory_order_acq_rel, memory_order_acquire)) | |
47 | { | |
48 | // We have set the flag to in_progress | |
49 | return true; | |
50 | } | |
51 | else if (expected == initialized) | |
52 | { | |
53 | // Another thread managed to complete the initialization | |
54 | return false; | |
55 | } | |
56 | else | |
57 | { | |
58 | // Wait until the initialization is complete | |
59 | //pthread::pthread_mutex_scoped_lock lk(&once_mutex); | |
60 | BOOST_VERIFY(!pthread_cond_wait(&once_cv, &once_mutex)); | |
61 | } | |
62 | } | |
63 | } | |
64 | } | |
65 | return false; | |
66 | } | |
67 | ||
68 | BOOST_THREAD_DECL void commit_once_region(once_flag& flag) BOOST_NOEXCEPT | |
69 | { | |
70 | atomic_type& f = get_atomic_storage(flag); | |
71 | { | |
72 | pthread::pthread_mutex_scoped_lock lk(&once_mutex); | |
73 | f.store(initialized, memory_order_release); | |
74 | } | |
75 | BOOST_VERIFY(!pthread_cond_broadcast(&once_cv)); | |
76 | } | |
77 | ||
78 | BOOST_THREAD_DECL void rollback_once_region(once_flag& flag) BOOST_NOEXCEPT | |
79 | { | |
80 | atomic_type& f = get_atomic_storage(flag); | |
81 | { | |
82 | pthread::pthread_mutex_scoped_lock lk(&once_mutex); | |
83 | f.store(uninitialized, memory_order_release); | |
84 | } | |
85 | BOOST_VERIFY(!pthread_cond_broadcast(&once_cv)); | |
86 | } | |
87 | ||
88 | } // namespace thread_detail | |
89 | ||
90 | } // namespace boost |