libstdc++
std_mutex.h
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1 // std::mutex implementation -*- C++ -*-
2 
3 // Copyright (C) 2003-2021 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  // Implementation details for std::condition_variable
127  class __condvar
128  {
129  using timespec = __gthread_time_t;
130 
131  public:
132  __condvar() noexcept
133  {
134 #ifndef __GTHREAD_COND_INIT
135  __GTHREAD_COND_INIT_FUNCTION(&_M_cond);
136 #endif
137  }
138 
139  ~__condvar()
140  {
141  int __e __attribute__((__unused__)) = __gthread_cond_destroy(&_M_cond);
142  __glibcxx_assert(__e != EBUSY); // threads are still blocked
143  }
144 
145  __condvar(const __condvar&) = delete;
146  __condvar& operator=(const __condvar&) = delete;
147 
148  __gthread_cond_t* native_handle() noexcept { return &_M_cond; }
149 
150  // Expects: Calling thread has locked __m.
151  void
152  wait(mutex& __m) noexcept
153  {
154  int __e __attribute__((__unused__))
155  = __gthread_cond_wait(&_M_cond, __m.native_handle());
156  __glibcxx_assert(__e == 0);
157  }
158 
159  void
160  wait_until(mutex& __m, timespec& __abs_time) noexcept
161  {
162  __gthread_cond_timedwait(&_M_cond, __m.native_handle(), &__abs_time);
163  }
164 
165 #ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
166  void
167  wait_until(mutex& __m, clockid_t __clock, timespec& __abs_time) noexcept
168  {
169  pthread_cond_clockwait(&_M_cond, __m.native_handle(), __clock,
170  &__abs_time);
171  }
172 #endif
173 
174  void
175  notify_one() noexcept
176  {
177  int __e __attribute__((__unused__)) = __gthread_cond_signal(&_M_cond);
178  __glibcxx_assert(__e == 0);
179  }
180 
181  void
182  notify_all() noexcept
183  {
184  int __e __attribute__((__unused__)) = __gthread_cond_broadcast(&_M_cond);
185  __glibcxx_assert(__e == 0);
186  }
187 
188  protected:
189 #ifdef __GTHREAD_COND_INIT
190  __gthread_cond_t _M_cond = __GTHREAD_COND_INIT;
191 #else
192  __gthread_cond_t _M_cond;
193 #endif
194  };
195 
196 #endif // _GLIBCXX_HAS_GTHREADS
197 
198  /// Do not acquire ownership of the mutex.
199  struct defer_lock_t { explicit defer_lock_t() = default; };
200 
201  /// Try to acquire ownership of the mutex without blocking.
202  struct try_to_lock_t { explicit try_to_lock_t() = default; };
203 
204  /// Assume the calling thread has already obtained mutex ownership
205  /// and manage it.
206  struct adopt_lock_t { explicit adopt_lock_t() = default; };
207 
208  /// Tag used to prevent a scoped lock from acquiring ownership of a mutex.
209  _GLIBCXX17_INLINE constexpr defer_lock_t defer_lock { };
210 
211  /// Tag used to prevent a scoped lock from blocking if a mutex is locked.
212  _GLIBCXX17_INLINE constexpr try_to_lock_t try_to_lock { };
213 
214  /// Tag used to make a scoped lock take ownership of a locked mutex.
215  _GLIBCXX17_INLINE constexpr adopt_lock_t adopt_lock { };
216 
217  /** @brief A simple scoped lock type.
218  *
219  * A lock_guard controls mutex ownership within a scope, releasing
220  * ownership in the destructor.
221  */
222  template<typename _Mutex>
224  {
225  public:
226  typedef _Mutex mutex_type;
227 
228  explicit lock_guard(mutex_type& __m) : _M_device(__m)
229  { _M_device.lock(); }
230 
231  lock_guard(mutex_type& __m, adopt_lock_t) noexcept : _M_device(__m)
232  { } // calling thread owns mutex
233 
234  ~lock_guard()
235  { _M_device.unlock(); }
236 
237  lock_guard(const lock_guard&) = delete;
238  lock_guard& operator=(const lock_guard&) = delete;
239 
240  private:
241  mutex_type& _M_device;
242  };
243 
244  /// @} group mutexes
245 _GLIBCXX_END_NAMESPACE_VERSION
246 } // namespace
247 #endif // C++11
248 #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:212
constexpr adopt_lock_t adopt_lock
Tag used to make a scoped lock take ownership of a locked mutex.
Definition: std_mutex.h:215
constexpr defer_lock_t defer_lock
Tag used to prevent a scoped lock from acquiring ownership of a mutex.
Definition: std_mutex.h:209
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:199
Try to acquire ownership of the mutex without blocking.
Definition: std_mutex.h:202
Assume the calling thread has already obtained mutex ownership and manage it.
Definition: std_mutex.h:206
A simple scoped lock type.
Definition: std_mutex.h:224