libstdc++
std_mutex.h
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1 // std::mutex implementation -*- C++ -*-
2 
3 // Copyright (C) 2003-2023 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 <errno.h> // EBUSY
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  /// @cond undocumented
57 
58  // Common base class for std::mutex and std::timed_mutex
59  class __mutex_base
60  {
61  protected:
62  typedef __gthread_mutex_t __native_type;
63 
64 #ifdef __GTHREAD_MUTEX_INIT
65  __native_type _M_mutex = __GTHREAD_MUTEX_INIT;
66 
67  constexpr __mutex_base() noexcept = default;
68 #else
69  __native_type _M_mutex;
70 
71  __mutex_base() noexcept
72  {
73  // XXX EAGAIN, ENOMEM, EPERM, EBUSY(may), EINVAL(may)
74  __GTHREAD_MUTEX_INIT_FUNCTION(&_M_mutex);
75  }
76 
77  ~__mutex_base() noexcept { __gthread_mutex_destroy(&_M_mutex); }
78 #endif
79 
80  __mutex_base(const __mutex_base&) = delete;
81  __mutex_base& operator=(const __mutex_base&) = delete;
82  };
83  /// @endcond
84 
85  /** The standard mutex type.
86  *
87  * A simple, non-recursive, non-timed mutex.
88  *
89  * Do not call `lock()` and `unlock()` directly, use a scoped lock type
90  * such as `std::unique_lock`, `std::lock_guard`, or (since C++17)
91  * `std::scoped_lock`.
92  *
93  * @headerfile mutex
94  * @since C++11
95  */
96  class mutex : private __mutex_base
97  {
98  public:
99  typedef __native_type* native_handle_type;
100 
101 #ifdef __GTHREAD_MUTEX_INIT
102  constexpr
103 #endif
104  mutex() noexcept = default;
105  ~mutex() = default;
106 
107  mutex(const mutex&) = delete;
108  mutex& operator=(const mutex&) = delete;
109 
110  void
111  lock()
112  {
113  int __e = __gthread_mutex_lock(&_M_mutex);
114 
115  // EINVAL, EAGAIN, EBUSY, EINVAL, EDEADLK(may)
116  if (__e)
117  __throw_system_error(__e);
118  }
119 
120  _GLIBCXX_NODISCARD
121  bool
122  try_lock() noexcept
123  {
124  // XXX EINVAL, EAGAIN, EBUSY
125  return !__gthread_mutex_trylock(&_M_mutex);
126  }
127 
128  void
129  unlock()
130  {
131  // XXX EINVAL, EAGAIN, EPERM
132  __gthread_mutex_unlock(&_M_mutex);
133  }
134 
135  native_handle_type
136  native_handle() noexcept
137  { return &_M_mutex; }
138  };
139 
140  /// @cond undocumented
141 
142  // Implementation details for std::condition_variable
143  class __condvar
144  {
145  using timespec = __gthread_time_t;
146 
147  public:
148  __condvar() noexcept
149  {
150 #ifndef __GTHREAD_COND_INIT
151  __GTHREAD_COND_INIT_FUNCTION(&_M_cond);
152 #endif
153  }
154 
155  ~__condvar()
156  {
157  int __e __attribute__((__unused__)) = __gthread_cond_destroy(&_M_cond);
158  __glibcxx_assert(__e != EBUSY); // threads are still blocked
159  }
160 
161  __condvar(const __condvar&) = delete;
162  __condvar& operator=(const __condvar&) = delete;
163 
164  __gthread_cond_t* native_handle() noexcept { return &_M_cond; }
165 
166  // Expects: Calling thread has locked __m.
167  void
168  wait(mutex& __m)
169  {
170  int __e __attribute__((__unused__))
171  = __gthread_cond_wait(&_M_cond, __m.native_handle());
172  __glibcxx_assert(__e == 0);
173  }
174 
175  void
176  wait_until(mutex& __m, timespec& __abs_time)
177  {
178  __gthread_cond_timedwait(&_M_cond, __m.native_handle(), &__abs_time);
179  }
180 
181 #ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
182  void
183  wait_until(mutex& __m, clockid_t __clock, timespec& __abs_time)
184  {
185  pthread_cond_clockwait(&_M_cond, __m.native_handle(), __clock,
186  &__abs_time);
187  }
188 #endif
189 
190  void
191  notify_one() noexcept
192  {
193  int __e __attribute__((__unused__)) = __gthread_cond_signal(&_M_cond);
194  __glibcxx_assert(__e == 0);
195  }
196 
197  void
198  notify_all() noexcept
199  {
200  int __e __attribute__((__unused__)) = __gthread_cond_broadcast(&_M_cond);
201  __glibcxx_assert(__e == 0);
202  }
203 
204  protected:
205 #ifdef __GTHREAD_COND_INIT
206  __gthread_cond_t _M_cond = __GTHREAD_COND_INIT;
207 #else
208  __gthread_cond_t _M_cond;
209 #endif
210  };
211  /// @endcond
212 
213 #endif // _GLIBCXX_HAS_GTHREADS
214 
215  /// Do not acquire ownership of the mutex.
216  struct defer_lock_t { explicit defer_lock_t() = default; };
217 
218  /// Try to acquire ownership of the mutex without blocking.
219  struct try_to_lock_t { explicit try_to_lock_t() = default; };
220 
221  /// Assume the calling thread has already obtained mutex ownership
222  /// and manage it.
223  struct adopt_lock_t { explicit adopt_lock_t() = default; };
224 
225  /// Tag used to prevent a scoped lock from acquiring ownership of a mutex.
226  _GLIBCXX17_INLINE constexpr defer_lock_t defer_lock { };
227 
228  /// Tag used to prevent a scoped lock from blocking if a mutex is locked.
229  _GLIBCXX17_INLINE constexpr try_to_lock_t try_to_lock { };
230 
231  /// Tag used to make a scoped lock take ownership of a locked mutex.
232  _GLIBCXX17_INLINE constexpr adopt_lock_t adopt_lock { };
233 
234  /** @brief A simple scoped lock type.
235  *
236  * A lock_guard controls mutex ownership within a scope, releasing
237  * ownership in the destructor.
238  *
239  * @headerfile mutex
240  * @since C++11
241  */
242  template<typename _Mutex>
244  {
245  public:
246  typedef _Mutex mutex_type;
247 
248  explicit lock_guard(mutex_type& __m) : _M_device(__m)
249  { _M_device.lock(); }
250 
251  lock_guard(mutex_type& __m, adopt_lock_t) noexcept : _M_device(__m)
252  { } // calling thread owns mutex
253 
254  ~lock_guard()
255  { _M_device.unlock(); }
256 
257  lock_guard(const lock_guard&) = delete;
258  lock_guard& operator=(const lock_guard&) = delete;
259 
260  private:
261  mutex_type& _M_device;
262  };
263 
264  /// @} group mutexes
265 _GLIBCXX_END_NAMESPACE_VERSION
266 } // namespace
267 #endif // C++11
268 #endif // _GLIBCXX_MUTEX_H
constexpr defer_lock_t defer_lock
Tag used to prevent a scoped lock from acquiring ownership of a mutex.
Definition: std_mutex.h:226
Try to acquire ownership of the mutex without blocking.
Definition: std_mutex.h:219
A simple scoped lock type.
Definition: std_mutex.h:243
Do not acquire ownership of the mutex.
Definition: std_mutex.h:216
Assume the calling thread has already obtained mutex ownership and manage it.
Definition: std_mutex.h:223
constexpr adopt_lock_t adopt_lock
Tag used to make a scoped lock take ownership of a locked mutex.
Definition: std_mutex.h:232
ISO C++ entities toplevel namespace is std.
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:229