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
_GLIBCXX_VISIBILITY(default)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>
223 class lock_guard
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
249