1//////////////////////////////////////////////////////////////////////////////
2//
3// (C) Copyright Ion Gaztanaga 2005-2012. Distributed under the Boost
4// Software License, Version 1.0. (See accompanying file
5// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6//
7// See http://www.boost.org/libs/interprocess for documentation.
8//
9//////////////////////////////////////////////////////////////////////////////
10
11#ifndef BOOST_INTERPROCESS_DETAIL_SPIN_MUTEX_HPP
12#define BOOST_INTERPROCESS_DETAIL_SPIN_MUTEX_HPP
13
14#ifndef BOOST_CONFIG_HPP
15# include <boost/config.hpp>
16#endif
17#
18#if defined(BOOST_HAS_PRAGMA_ONCE)
19# pragma once
20#endif
21
22#include <boost/interprocess/detail/config_begin.hpp>
23#include <boost/interprocess/detail/workaround.hpp>
24#include <boost/assert.hpp>
25#include <boost/interprocess/detail/atomic.hpp>
26#include <boost/cstdint.hpp>
27#include <boost/interprocess/detail/os_thread_functions.hpp>
28#include <boost/interprocess/sync/detail/common_algorithms.hpp>
29#include <boost/interprocess/timed_utils.hpp>
30
31namespace boost {
32namespace interprocess {
33namespace ipcdetail {
34
35class spin_mutex
36{
37 spin_mutex(const spin_mutex &);
38 spin_mutex &operator=(const spin_mutex &);
39 public:
40
41 spin_mutex();
42 ~spin_mutex();
43
44 void lock();
45 bool try_lock();
46 template<class TimePoint>
47 bool timed_lock(const TimePoint &abs_time);
48
49 template<class TimePoint> bool try_lock_until(const TimePoint &abs_time)
50 { return this->timed_lock(abs_time); }
51
52 template<class Duration> bool try_lock_for(const Duration &dur)
53 { return this->timed_lock(duration_to_ustime(dur)); }
54
55 void unlock();
56 void take_ownership(){}
57 private:
58 volatile boost::uint32_t m_s;
59
60 struct common_lock_wrapper
61 {
62 common_lock_wrapper(spin_mutex &sp)
63 : m_sp(sp)
64 {}
65
66 void lock()
67 {
68 ipcdetail::try_based_lock(m&: m_sp);
69 }
70
71 template<class TimePoint>
72 bool timed_lock(const TimePoint &abs_time)
73 { return m_sp.timed_lock(abs_time); }
74
75 spin_mutex &m_sp;
76 };
77};
78
79inline spin_mutex::spin_mutex()
80 : m_s(0)
81{
82 //Note that this class is initialized to zero.
83 //So zeroed memory can be interpreted as an
84 //initialized mutex
85}
86
87inline spin_mutex::~spin_mutex()
88{
89 //Trivial destructor
90}
91
92inline void spin_mutex::lock(void)
93{
94 common_lock_wrapper clw(*this);
95 ipcdetail::timeout_when_locking_aware_lock(m&: clw);
96}
97
98inline bool spin_mutex::try_lock(void)
99{
100 boost::uint32_t prev_s = ipcdetail::atomic_cas32(mem: const_cast<boost::uint32_t*>(&m_s), with: 1, cmp: 0);
101 return m_s == 1 && prev_s == 0;
102}
103
104template<class TimePoint>
105inline bool spin_mutex::timed_lock(const TimePoint &abs_time)
106{ return ipcdetail::try_based_timed_lock(*this, abs_time); }
107
108inline void spin_mutex::unlock(void)
109{ ipcdetail::atomic_cas32(mem: const_cast<boost::uint32_t*>(&m_s), with: 0, cmp: 1); }
110
111} //namespace ipcdetail {
112} //namespace interprocess {
113} //namespace boost {
114
115#include <boost/interprocess/detail/config_end.hpp>
116
117#endif //BOOST_INTERPROCESS_DETAIL_SPIN_MUTEX_HPP
118

source code of boost/libs/interprocess/include/boost/interprocess/sync/spin/mutex.hpp