libstdc++
std_mutex.h
Go to the documentation of this file.
1 // std::mutex implementation -*- C++ -*-
2 
3 // Copyright (C) 2003-2020 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 /** @file bits/std_mutex.h
26  * This is an internal header file, included by other library headers.
27  * Do not attempt to use it directly. @headername{mutex}
28  */
29 
30 #ifndef _GLIBCXX_MUTEX_H
31 #define _GLIBCXX_MUTEX_H 1
32 
33 #pragma GCC system_header
34 
35 #if __cplusplus < 201103L
36 # include <bits/c++0x_warning.h>
37 #else
38 
39 #include <system_error>
40 #include <bits/functexcept.h>
41 #include <bits/gthr.h>
42 
43 namespace std _GLIBCXX_VISIBILITY(default)
44 {
45 _GLIBCXX_BEGIN_NAMESPACE_VERSION
46 
47  /**
48  * @defgroup mutexes Mutexes
49  * @ingroup concurrency
50  *
51  * Classes for mutex support.
52  * @{
53  */
54 
55 #ifdef _GLIBCXX_HAS_GTHREADS
56  // Common base class for std::mutex and std::timed_mutex
57  class __mutex_base
58  {
59  protected:
60  typedef __gthread_mutex_t __native_type;
61 
62 #ifdef __GTHREAD_MUTEX_INIT
63  __native_type _M_mutex = __GTHREAD_MUTEX_INIT;
64 
65  constexpr __mutex_base() noexcept = default;
66 #else
67  __native_type _M_mutex;
68 
69  __mutex_base() noexcept
70  {
71  // XXX EAGAIN, ENOMEM, EPERM, EBUSY(may), EINVAL(may)
72  __GTHREAD_MUTEX_INIT_FUNCTION(&_M_mutex);
73  }
74 
75  ~__mutex_base() noexcept { __gthread_mutex_destroy(&_M_mutex); }
76 #endif
77 
78  __mutex_base(const __mutex_base&) = delete;
79  __mutex_base& operator=(const __mutex_base&) = delete;
80  };
81 
82  /// The standard mutex type.
83  class mutex : private __mutex_base
84  {
85  public:
86  typedef __native_type* native_handle_type;
87 
88 #ifdef __GTHREAD_MUTEX_INIT
89  constexpr
90 #endif
91  mutex() noexcept = default;
92  ~mutex() = default;
93 
94  mutex(const mutex&) = delete;
95  mutex& operator=(const mutex&) = delete;
96 
97  void
98  lock()
99  {
100  int __e = __gthread_mutex_lock(&_M_mutex);
101 
102  // EINVAL, EAGAIN, EBUSY, EINVAL, EDEADLK(may)
103  if (__e)
104  __throw_system_error(__e);
105  }
106 
107  bool
108  try_lock() noexcept
109  {
110  // XXX EINVAL, EAGAIN, EBUSY
111  return !__gthread_mutex_trylock(&_M_mutex);
112  }
113 
114  void
115  unlock()
116  {
117  // XXX EINVAL, EAGAIN, EPERM
118  __gthread_mutex_unlock(&_M_mutex);
119  }
120 
121  native_handle_type
122  native_handle() noexcept
123  { return &_M_mutex; }
124  };
125 
126 #endif // _GLIBCXX_HAS_GTHREADS
127 
128  /// Do not acquire ownership of the mutex.
129  struct defer_lock_t { explicit defer_lock_t() = default; };
130 
131  /// Try to acquire ownership of the mutex without blocking.
132  struct try_to_lock_t { explicit try_to_lock_t() = default; };
133 
134  /// Assume the calling thread has already obtained mutex ownership
135  /// and manage it.
136  struct adopt_lock_t { explicit adopt_lock_t() = default; };
137 
138  /// Tag used to prevent a scoped lock from acquiring ownership of a mutex.
139  _GLIBCXX17_INLINE constexpr defer_lock_t defer_lock { };
140 
141  /// Tag used to prevent a scoped lock from blocking if a mutex is locked.
142  _GLIBCXX17_INLINE constexpr try_to_lock_t try_to_lock { };
143 
144  /// Tag used to make a scoped lock take ownership of a locked mutex.
145  _GLIBCXX17_INLINE constexpr adopt_lock_t adopt_lock { };
146 
147  /** @brief A simple scoped lock type.
148  *
149  * A lock_guard controls mutex ownership within a scope, releasing
150  * ownership in the destructor.
151  */
152  template<typename _Mutex>
154  {
155  public:
156  typedef _Mutex mutex_type;
157 
158  explicit lock_guard(mutex_type& __m) : _M_device(__m)
159  { _M_device.lock(); }
160 
161  lock_guard(mutex_type& __m, adopt_lock_t) noexcept : _M_device(__m)
162  { } // calling thread owns mutex
163 
164  ~lock_guard()
165  { _M_device.unlock(); }
166 
167  lock_guard(const lock_guard&) = delete;
168  lock_guard& operator=(const lock_guard&) = delete;
169 
170  private:
171  mutex_type& _M_device;
172  };
173 
174  /// @} group mutexes
175 _GLIBCXX_END_NAMESPACE_VERSION
176 } // namespace
177 #endif // C++11
178 #endif // _GLIBCXX_MUTEX_H
constexpr try_to_lock_t try_to_lock
Tag used to prevent a scoped lock from blocking if a mutex is locked.
Definition: std_mutex.h:142
constexpr adopt_lock_t adopt_lock
Tag used to make a scoped lock take ownership of a locked mutex.
Definition: std_mutex.h:145
constexpr defer_lock_t defer_lock
Tag used to prevent a scoped lock from acquiring ownership of a mutex.
Definition: std_mutex.h:139
ISO C++ entities toplevel namespace is std.
The standard mutex type.
Definition: std_mutex.h:84
Do not acquire ownership of the mutex.
Definition: std_mutex.h:129
Try to acquire ownership of the mutex without blocking.
Definition: std_mutex.h:132
Assume the calling thread has already obtained mutex ownership and manage it.
Definition: std_mutex.h:136
A simple scoped lock type.
Definition: std_mutex.h:154