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The C and C++ Include Header Files
cat -n /usr/include/c++/15/condition_variable
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 56 namespace 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 static_cast<std::time_t>(__s.time_since_epoch().count()), 202 static_cast<long>(__ns.count()) 203 }; 204 205 _M_cond.wait_until(*__lock.mutex(), CLOCK_MONOTONIC, __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 static_cast<std::time_t>(__s.time_since_epoch().count()), 223 static_cast<long>(__ns.count()) 224 }; 225 226 _M_cond.wait_until(*__lock.mutex(), __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(__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(__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
