1// <condition_variable> -*- C++ -*-
2
3// Copyright (C) 2008-2025 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 include/condition_variable
26 * This is a Standard C++ Library header.
27 */
28
29#ifndef _GLIBCXX_CONDITION_VARIABLE
30#define _GLIBCXX_CONDITION_VARIABLE 1
31
32#ifdef _GLIBCXX_SYSHDR
33#pragma GCC system_header
34#endif
35
36#include <bits/requires_hosted.h> // threading primitive
37
38#if __cplusplus < 201103L
39# include <bits/c++0x_warning.h>
40#else
41
42#include <bits/chrono.h>
43#include <bits/error_constants.h>
44#include <bits/std_mutex.h>
45#include <bits/unique_lock.h>
46#include <bits/alloc_traits.h>
47#include <bits/shared_ptr.h>
48#include <bits/cxxabi_forced.h>
49
50#if __cplusplus > 201703L
51# include <stop_token>
52#endif
53
54#if defined(_GLIBCXX_HAS_GTHREADS)
55
56namespace std _GLIBCXX_VISIBILITY(default)
57{
58_GLIBCXX_BEGIN_NAMESPACE_VERSION
59
60 /**
61 * @defgroup condition_variables Condition Variables
62 * @ingroup concurrency
63 *
64 * Classes for condition_variable support.
65 * @{
66 */
67
68 /// cv_status
69 enum class cv_status { no_timeout, timeout };
70
71 /// condition_variable
72 class condition_variable
73 {
74 using steady_clock = chrono::steady_clock;
75 using system_clock = chrono::system_clock;
76#ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
77 using __clock_t = steady_clock;
78#else
79 using __clock_t = system_clock;
80#endif
81
82 __condvar _M_cond;
83
84 public:
85 typedef __gthread_cond_t* native_handle_type;
86
87 condition_variable() noexcept;
88 ~condition_variable() noexcept;
89
90 condition_variable(const condition_variable&) = delete;
91 condition_variable& operator=(const condition_variable&) = delete;
92
93 void
94 notify_one() noexcept;
95
96 void
97 notify_all() noexcept;
98
99 void
100 wait(unique_lock<mutex>& __lock);
101
102 template<typename _Predicate>
103 void
104 wait(unique_lock<mutex>& __lock, _Predicate __p)
105 {
106 while (!__p())
107 wait(__lock);
108 }
109
110#ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
111 template<typename _Duration>
112 cv_status
113 wait_until(unique_lock<mutex>& __lock,
114 const chrono::time_point<steady_clock, _Duration>& __atime)
115 { return __wait_until_impl(__lock, __atime); }
116#endif
117
118 template<typename _Duration>
119 cv_status
120 wait_until(unique_lock<mutex>& __lock,
121 const chrono::time_point<system_clock, _Duration>& __atime)
122 { return __wait_until_impl(__lock, __atime); }
123
124 template<typename _Clock, typename _Duration>
125 cv_status
126 wait_until(unique_lock<mutex>& __lock,
127 const chrono::time_point<_Clock, _Duration>& __atime)
128 {
129#if __cplusplus > 201703L
130 static_assert(chrono::is_clock_v<_Clock>);
131#endif
132 using __s_dur = typename __clock_t::duration;
133 const typename _Clock::time_point __c_entry = _Clock::now();
134 const __clock_t::time_point __s_entry = __clock_t::now();
135 const auto __delta = __atime - __c_entry;
136 const auto __s_atime = __s_entry +
137 chrono::__detail::ceil<__s_dur>(__delta);
138
139 if (__wait_until_impl(__lock, __s_atime) == cv_status::no_timeout)
140 return cv_status::no_timeout;
141 // We got a timeout when measured against __clock_t but
142 // we need to check against the caller-supplied clock
143 // to tell whether we should return a timeout.
144 if (_Clock::now() < __atime)
145 return cv_status::no_timeout;
146 return cv_status::timeout;
147 }
148
149 template<typename _Clock, typename _Duration, typename _Predicate>
150 bool
151 wait_until(unique_lock<mutex>& __lock,
152 const chrono::time_point<_Clock, _Duration>& __atime,
153 _Predicate __p)
154 {
155 while (!__p())
156 if (wait_until(__lock, __atime) == cv_status::timeout)
157 return __p();
158 return true;
159 }
160
161 template<typename _Rep, typename _Period>
162 cv_status
163 wait_for(unique_lock<mutex>& __lock,
164 const chrono::duration<_Rep, _Period>& __rtime)
165 {
166 using __dur = typename steady_clock::duration;
167 return wait_until(__lock,
168 steady_clock::now() +
169 chrono::__detail::ceil<__dur>(__rtime));
170 }
171
172 template<typename _Rep, typename _Period, typename _Predicate>
173 bool
174 wait_for(unique_lock<mutex>& __lock,
175 const chrono::duration<_Rep, _Period>& __rtime,
176 _Predicate __p)
177 {
178 using __dur = typename steady_clock::duration;
179 return wait_until(__lock,
180 steady_clock::now() +
181 chrono::__detail::ceil<__dur>(__rtime),
182 std::move(__p));
183 }
184
185 native_handle_type
186 native_handle()
187 { return _M_cond.native_handle(); }
188
189 private:
190#ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
191 template<typename _Dur>
192 cv_status
193 __wait_until_impl(unique_lock<mutex>& __lock,
194 const chrono::time_point<steady_clock, _Dur>& __atime)
195 {
196 auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
197 auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
198
199 __gthread_time_t __ts =
200 {
201 .tv_sec: static_cast<std::time_t>(__s.time_since_epoch().count()),
202 .tv_nsec: static_cast<long>(__ns.count())
203 };
204
205 _M_cond.wait_until(m&: *__lock.mutex(), CLOCK_MONOTONIC, abs_time&: __ts);
206
207 return (steady_clock::now() < __atime
208 ? cv_status::no_timeout : cv_status::timeout);
209 }
210#endif
211
212 template<typename _Dur>
213 cv_status
214 __wait_until_impl(unique_lock<mutex>& __lock,
215 const chrono::time_point<system_clock, _Dur>& __atime)
216 {
217 auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
218 auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
219
220 __gthread_time_t __ts =
221 {
222 .tv_sec: static_cast<std::time_t>(__s.time_since_epoch().count()),
223 .tv_nsec: static_cast<long>(__ns.count())
224 };
225
226 _M_cond.wait_until(m&: *__lock.mutex(), abs_time&: __ts);
227
228 return (system_clock::now() < __atime
229 ? cv_status::no_timeout : cv_status::timeout);
230 }
231 };
232
233 void
234 notify_all_at_thread_exit(condition_variable&, unique_lock<mutex>);
235
236 struct __at_thread_exit_elt
237 {
238 __at_thread_exit_elt* _M_next;
239 void (*_M_cb)(void*);
240 };
241
242_GLIBCXX_BEGIN_INLINE_ABI_NAMESPACE(_V2)
243
244 /// condition_variable_any
245 // Like above, but mutex is not required to have try_lock.
246 class condition_variable_any
247 {
248#ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
249 using __clock_t = chrono::steady_clock;
250#else
251 using __clock_t = chrono::system_clock;
252#endif
253 condition_variable _M_cond;
254 shared_ptr<mutex> _M_mutex;
255
256 // scoped unlock - unlocks in ctor, re-locks in dtor
257 template<typename _Lock>
258 struct _Unlock
259 {
260 explicit _Unlock(_Lock& __lk) : _M_lock(__lk) { __lk.unlock(); }
261
262#pragma GCC diagnostic push
263#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
264 ~_Unlock() noexcept(false)
265 {
266 if (uncaught_exception())
267 {
268 __try
269 { _M_lock.lock(); }
270 __catch(const __cxxabiv1::__forced_unwind&)
271 { __throw_exception_again; }
272 __catch(...)
273 { }
274 }
275 else
276 _M_lock.lock();
277 }
278#pragma GCC diagnostic pop
279
280 _Unlock(const _Unlock&) = delete;
281 _Unlock& operator=(const _Unlock&) = delete;
282
283 _Lock& _M_lock;
284 };
285
286 public:
287 condition_variable_any() : _M_mutex(std::make_shared<mutex>()) { }
288 ~condition_variable_any() = default;
289
290 condition_variable_any(const condition_variable_any&) = delete;
291 condition_variable_any& operator=(const condition_variable_any&) = delete;
292
293 void
294 notify_one() noexcept
295 {
296 lock_guard<mutex> __lock(*_M_mutex);
297 _M_cond.notify_one();
298 }
299
300 void
301 notify_all() noexcept
302 {
303 lock_guard<mutex> __lock(*_M_mutex);
304 _M_cond.notify_all();
305 }
306
307 template<typename _Lock>
308 void
309 wait(_Lock& __lock)
310 {
311 shared_ptr<mutex> __mutex = _M_mutex;
312 unique_lock<mutex> __my_lock(*__mutex);
313 _Unlock<_Lock> __unlock(__lock);
314 // *__mutex must be unlocked before re-locking __lock so move
315 // ownership of *__mutex lock to an object with shorter lifetime.
316 unique_lock<mutex> __my_lock2(std::move(__my_lock));
317 _M_cond.wait(lock&: __my_lock2);
318 }
319
320
321 template<typename _Lock, typename _Predicate>
322 void
323 wait(_Lock& __lock, _Predicate __p)
324 {
325 while (!__p())
326 wait(__lock);
327 }
328
329 template<typename _Lock, typename _Clock, typename _Duration>
330 cv_status
331 wait_until(_Lock& __lock,
332 const chrono::time_point<_Clock, _Duration>& __atime)
333 {
334 shared_ptr<mutex> __mutex = _M_mutex;
335 unique_lock<mutex> __my_lock(*__mutex);
336 _Unlock<_Lock> __unlock(__lock);
337 // *__mutex must be unlocked before re-locking __lock so move
338 // ownership of *__mutex lock to an object with shorter lifetime.
339 unique_lock<mutex> __my_lock2(std::move(__my_lock));
340 return _M_cond.wait_until(__my_lock2, __atime);
341 }
342
343 template<typename _Lock, typename _Clock,
344 typename _Duration, typename _Predicate>
345 bool
346 wait_until(_Lock& __lock,
347 const chrono::time_point<_Clock, _Duration>& __atime,
348 _Predicate __p)
349 {
350 while (!__p())
351 if (wait_until(__lock, __atime) == cv_status::timeout)
352 return __p();
353 return true;
354 }
355
356 template<typename _Lock, typename _Rep, typename _Period>
357 cv_status
358 wait_for(_Lock& __lock, const chrono::duration<_Rep, _Period>& __rtime)
359 { return wait_until(__lock, __clock_t::now() + __rtime); }
360
361 template<typename _Lock, typename _Rep,
362 typename _Period, typename _Predicate>
363 bool
364 wait_for(_Lock& __lock,
365 const chrono::duration<_Rep, _Period>& __rtime, _Predicate __p)
366 { return wait_until(__lock, __clock_t::now() + __rtime, std::move(__p)); }
367
368#ifdef __glibcxx_jthread
369 template <class _Lock, class _Predicate>
370 bool wait(_Lock& __lock,
371 stop_token __stoken,
372 _Predicate __p)
373 {
374 if (__stoken.stop_requested())
375 {
376 return __p();
377 }
378
379 std::stop_callback __cb(__stoken, [this] { notify_all(); });
380 shared_ptr<mutex> __mutex = _M_mutex;
381 while (!__p())
382 {
383 unique_lock<mutex> __my_lock(*__mutex);
384 if (__stoken.stop_requested())
385 {
386 return false;
387 }
388 // *__mutex must be unlocked before re-locking __lock so move
389 // ownership of *__mutex lock to an object with shorter lifetime.
390 _Unlock<_Lock> __unlock(__lock);
391 unique_lock<mutex> __my_lock2(std::move(__my_lock));
392 _M_cond.wait(lock&: __my_lock2);
393 }
394 return true;
395 }
396
397 template <class _Lock, class _Clock, class _Duration, class _Predicate>
398 bool wait_until(_Lock& __lock,
399 stop_token __stoken,
400 const chrono::time_point<_Clock, _Duration>& __abs_time,
401 _Predicate __p)
402 {
403 if (__stoken.stop_requested())
404 {
405 return __p();
406 }
407
408 std::stop_callback __cb(__stoken, [this] { notify_all(); });
409 shared_ptr<mutex> __mutex = _M_mutex;
410 while (!__p())
411 {
412 bool __stop;
413 {
414 unique_lock<mutex> __my_lock(*__mutex);
415 if (__stoken.stop_requested())
416 {
417 return false;
418 }
419 _Unlock<_Lock> __u(__lock);
420 unique_lock<mutex> __my_lock2(std::move(__my_lock));
421 const auto __status = _M_cond.wait_until(__my_lock2, __abs_time);
422 __stop = (__status == std::cv_status::timeout) || __stoken.stop_requested();
423 }
424 if (__stop)
425 {
426 return __p();
427 }
428 }
429 return true;
430 }
431
432 template <class _Lock, class _Rep, class _Period, class _Predicate>
433 bool wait_for(_Lock& __lock,
434 stop_token __stoken,
435 const chrono::duration<_Rep, _Period>& __rel_time,
436 _Predicate __p)
437 {
438 auto __abst = std::chrono::steady_clock::now() + __rel_time;
439 return wait_until(__lock,
440 std::move(__stoken),
441 __abst,
442 std::move(__p));
443 }
444#endif
445 };
446
447_GLIBCXX_END_INLINE_ABI_NAMESPACE(_V2)
448
449 /// @} group condition_variables
450_GLIBCXX_END_NAMESPACE_VERSION
451} // namespace
452
453#endif // _GLIBCXX_HAS_GTHREADS
454#endif // C++11
455#endif // _GLIBCXX_CONDITION_VARIABLE
456