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1 // (C) Copyright 2012 Vicente J. Botet Escriba
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2 // Distributed under the Boost Software License, Version 1.0. (See
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3 // accompanying file LICENSE_1_0.txt or copy at
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4 // http://www.boost.org/LICENSE_1_0.txt)
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5
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6
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7 #ifndef BOOST_THREAD_TESTABLE_LOCKABLE_HPP
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8 #define BOOST_THREAD_TESTABLE_LOCKABLE_HPP
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9
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10 #include <boost/thread/detail/config.hpp>
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11
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12 #include <boost/thread/thread_only.hpp>
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13
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14 #include <boost/atomic.hpp>
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15 #include <boost/assert.hpp>
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16
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17 #include <boost/config/abi_prefix.hpp>
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18
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19 namespace boost
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20 {
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21 /**
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22 * Based on Associate Mutexes with Data to Prevent Races, By Herb Sutter, May 13, 2010
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23 * http://www.drdobbs.com/windows/associate-mutexes-with-data-to-prevent-r/224701827?pgno=3
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24 *
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25 * Make our mutex testable if it isn't already.
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26 *
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27 * Many mutex services (including boost::mutex) don't provide a way to ask,
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28 * "Do I already hold a lock on this mutex?"
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29 * Sometimes it is needed to know if a method like is_locked to be available.
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30 * This wrapper associates an arbitrary lockable type with a thread id that stores the ID of the thread that
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31 * currently holds the lockable. The thread id initially holds an invalid value that means no threads own the mutex.
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32 * When we acquire a lock, we set the thread id; and when we release a lock, we reset it back to its default no id state.
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33 *
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34 */
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35 template <typename Lockable>
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36 class testable_mutex
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37 {
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38 Lockable mtx_;
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39 atomic<thread::id> id_;
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40 public:
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41 /// the type of the wrapped lockable
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42 typedef Lockable lockable_type;
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43
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44 /// Non copyable
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45 BOOST_THREAD_NO_COPYABLE(testable_mutex)
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46
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47 testable_mutex() : id_(thread::id()) {}
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48
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49 void lock()
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50 {
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51 BOOST_ASSERT(! is_locked_by_this_thread());
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52 mtx_.lock();
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53 id_ = this_thread::get_id();
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54 }
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55
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56 void unlock()
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57 {
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58 BOOST_ASSERT(is_locked_by_this_thread());
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59 id_ = thread::id();
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60 mtx_.unlock();
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61 }
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62
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63 bool try_lock()
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64 {
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65 BOOST_ASSERT(! is_locked_by_this_thread());
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66 if (mtx_.try_lock())
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67 {
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68 id_ = this_thread::get_id();
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69 return true;
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70 }
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71 else
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72 {
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73 return false;
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74 }
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75 }
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76 #ifdef BOOST_THREAD_USES_CHRONO
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77 template <class Rep, class Period>
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78 bool try_lock_for(const chrono::duration<Rep, Period>& rel_time)
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79 {
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80 BOOST_ASSERT(! is_locked_by_this_thread());
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81 if (mtx_.try_lock_for(rel_time))
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82 {
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83 id_ = this_thread::get_id();
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84 return true;
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85 }
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86 else
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87 {
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88 return false;
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89 }
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90 }
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91 template <class Clock, class Duration>
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92 bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time)
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93 {
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94 BOOST_ASSERT(! is_locked_by_this_thread());
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95 if (mtx_.try_lock_until(abs_time))
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96 {
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97 id_ = this_thread::get_id();
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98 return true;
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99 }
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100 else
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101 {
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102 return false;
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103 }
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104 }
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105 #endif
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106
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107 bool is_locked_by_this_thread() const
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108 {
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109 return this_thread::get_id() == id_;
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110 }
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111 bool is_locked() const
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112 {
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113 return ! (thread::id() == id_);
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114 }
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115
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116 thread::id get_id() const
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117 {
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118 return id_;
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119 }
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120
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121 // todo add the shared and upgrade mutex functions
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122 };
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123
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124 template <typename Lockable>
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125 struct is_testable_lockable : false_type
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126 {};
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127
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128 template <typename Lockable>
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129 struct is_testable_lockable<testable_mutex<Lockable> > : true_type
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130 {};
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131
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132 // /**
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133 // * Overloaded function used to check if the mutex is locked when it is testable and do nothing otherwise.
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134 // *
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135 // * This function is used usually to assert the pre-condition when the function can only be called when the mutex
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136 // * must be locked by the current thread.
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137 // */
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138 // template <typename Lockable>
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139 // bool is_locked_by_this_thread(testable_mutex<Lockable> const& mtx)
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140 // {
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141 // return mtx.is_locked();
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142 // }
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143 // template <typename Lockable>
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144 // bool is_locked_by_this_thread(Lockable const&)
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145 // {
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146 // return true;
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147 // }
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148 }
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149
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150 #include <boost/config/abi_suffix.hpp>
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151
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152 #endif // header
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