libstdc++-v3/include/std/condition_variable

   1 // <condition_variable> -*- C++ -*-
   2
   3 // Copyright (C) 2008-2022 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 #pragma GCC system_header
  33
  34 #if __cplusplus < 201103L
  35 # include <bits/c++0x_warning.h>
  36 #else
  37
  38 #include <bits/chrono.h>
  39 #include <bits/std_mutex.h>
  40 #include <bits/unique_lock.h>
  41 #include <bits/alloc_traits.h>
  42 #include <bits/shared_ptr.h>
  43 #include <bits/cxxabi_forced.h>
  44
  45 #if __cplusplus > 201703L
  46 # include <stop_token>
  47 #endif
  48
  49 #if defined(_GLIBCXX_HAS_GTHREADS)
  50
  51 namespace std _GLIBCXX_VISIBILITY(default)
  52 {
  53 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  54
  55   /**
  56    * @defgroup condition_variables Condition Variables
  57    * @ingroup concurrency
  58    *
  59    * Classes for condition_variable support.
  60    * @{
  61    */
  62
  63   /// cv_status
  64   enum class cv_status { no_timeout, timeout };
  65
  66   /// condition_variable
  67   class condition_variable
  68   {
  69     using steady_clock = chrono::steady_clock;
  70     using system_clock = chrono::system_clock;
  71 #ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
  72     using __clock_t = steady_clock;
  73 #else
  74     using __clock_t = system_clock;
  75 #endif
  76
  77     __condvar _M_cond;
  78
  79   public:
  80     typedef __gthread_cond_t*           native_handle_type;
  81
  82     condition_variable() noexcept;
  83     ~condition_variable() noexcept;
  84
  85     condition_variable(const condition_variable&) = delete;
  86     condition_variable& operator=(const condition_variable&) = delete;
  87
  88     void
  89     notify_one() noexcept;
  90
  91     void
  92     notify_all() noexcept;
  93
  94     void
  95     wait(unique_lock<mutex>& __lock);
  96
  97     template<typename _Predicate>
  98       void
  99       wait(unique_lock<mutex>& __lock, _Predicate __p)
 100       {
 101         while (!__p())
 102           wait(__lock);
 103       }
 104
 105 #ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
 106     template<typename _Duration>
 107       cv_status
 108       wait_until(unique_lock<mutex>& __lock,
 109                  const chrono::time_point<steady_clock, _Duration>& __atime)
 110       { return __wait_until_impl(__lock, __atime); }
 111 #endif
 112
 113     template<typename _Duration>
 114       cv_status
 115       wait_until(unique_lock<mutex>& __lock,
 116                  const chrono::time_point<system_clock, _Duration>& __atime)
 117       { return __wait_until_impl(__lock, __atime); }
 118
 119     template<typename _Clock, typename _Duration>
 120       cv_status
 121       wait_until(unique_lock<mutex>& __lock,
 122                  const chrono::time_point<_Clock, _Duration>& __atime)
 123       {
 124 #if __cplusplus > 201703L
 125         static_assert(chrono::is_clock_v<_Clock>);
 126 #endif
 127         using __s_dur = typename __clock_t::duration;
 128         const typename _Clock::time_point __c_entry = _Clock::now();
 129         const __clock_t::time_point __s_entry = __clock_t::now();
 130         const auto __delta = __atime - __c_entry;
 131         const auto __s_atime = __s_entry +
 132           chrono::__detail::ceil<__s_dur>(__delta);
 133
 134         if (__wait_until_impl(__lock, __s_atime) == cv_status::no_timeout)
 135           return cv_status::no_timeout;
 136         // We got a timeout when measured against __clock_t but
 137         // we need to check against the caller-supplied clock
 138         // to tell whether we should return a timeout.
 139         if (_Clock::now() < __atime)
 140           return cv_status::no_timeout;
 141         return cv_status::timeout;
 142       }
 143
 144     template<typename _Clock, typename _Duration, typename _Predicate>
 145       bool
 146       wait_until(unique_lock<mutex>& __lock,
 147                  const chrono::time_point<_Clock, _Duration>& __atime,
 148                  _Predicate __p)
 149       {
 150         while (!__p())
 151           if (wait_until(__lock, __atime) == cv_status::timeout)
 152             return __p();
 153         return true;
 154       }
 155
 156     template<typename _Rep, typename _Period>
 157       cv_status
 158       wait_for(unique_lock<mutex>& __lock,
 159                const chrono::duration<_Rep, _Period>& __rtime)
 160       {
 161         using __dur = typename steady_clock::duration;
 162         return wait_until(__lock,
 163                           steady_clock::now() +
 164                           chrono::__detail::ceil<__dur>(__rtime));
 165       }
 166
 167     template<typename _Rep, typename _Period, typename _Predicate>
 168       bool
 169       wait_for(unique_lock<mutex>& __lock,
 170                const chrono::duration<_Rep, _Period>& __rtime,
 171                _Predicate __p)
 172       {
 173         using __dur = typename steady_clock::duration;
 174         return wait_until(__lock,
 175                           steady_clock::now() +
 176                           chrono::__detail::ceil<__dur>(__rtime),
 177                           std::move(__p));
 178       }
 179
 180     native_handle_type
 181     native_handle()
 182     { return _M_cond.native_handle(); }
 183
 184   private:
 185 #ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
 186     template<typename _Dur>
 187       cv_status
 188       __wait_until_impl(unique_lock<mutex>& __lock,
 189                         const chrono::time_point<steady_clock, _Dur>& __atime)
 190       {
 191         auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
 192         auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
 193
 194         __gthread_time_t __ts =
 195           {
 196             static_cast<std::time_t>(__s.time_since_epoch().count()),
 197             static_cast<long>(__ns.count())
 198           };
 199
 200         _M_cond.wait_until(*__lock.mutex(), CLOCK_MONOTONIC, __ts);
 201
 202         return (steady_clock::now() < __atime
 203                 ? cv_status::no_timeout : cv_status::timeout);
 204       }
 205 #endif
 206
 207     template<typename _Dur>
 208       cv_status
 209       __wait_until_impl(unique_lock<mutex>& __lock,
 210                         const chrono::time_point<system_clock, _Dur>& __atime)
 211       {
 212         auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
 213         auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
 214
 215         __gthread_time_t __ts =
 216           {
 217             static_cast<std::time_t>(__s.time_since_epoch().count()),
 218             static_cast<long>(__ns.count())
 219           };
 220
 221         _M_cond.wait_until(*__lock.mutex(), __ts);
 222
 223         return (system_clock::now() < __atime
 224                 ? cv_status::no_timeout : cv_status::timeout);
 225       }
 226   };
 227
 228   void
 229   notify_all_at_thread_exit(condition_variable&, unique_lock<mutex>);
 230
 231   struct __at_thread_exit_elt
 232   {
 233     __at_thread_exit_elt* _M_next;
 234     void (*_M_cb)(void*);
 235   };
 236
 237 _GLIBCXX_BEGIN_INLINE_ABI_NAMESPACE(_V2)
 238
 239   /// condition_variable_any
 240   // Like above, but mutex is not required to have try_lock.
 241   class condition_variable_any
 242   {
 243 #ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
 244     using __clock_t = chrono::steady_clock;
 245 #else
 246     using __clock_t = chrono::system_clock;
 247 #endif
 248     condition_variable                  _M_cond;
 249     shared_ptr<mutex>                   _M_mutex;
 250
 251     // scoped unlock - unlocks in ctor, re-locks in dtor
 252     template<typename _Lock>
 253       struct _Unlock
 254       {
 255         explicit _Unlock(_Lock& __lk) : _M_lock(__lk) { __lk.unlock(); }
 256
 257 #pragma GCC diagnostic push
 258 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
 259         ~_Unlock() noexcept(false)
 260         {
 261           if (uncaught_exception())
 262             {
 263               __try
 264               { _M_lock.lock(); }
 265               __catch(const __cxxabiv1::__forced_unwind&)
 266               { __throw_exception_again; }
 267               __catch(...)
 268               { }
 269             }
 270           else
 271             _M_lock.lock();
 272         }
 273 #pragma GCC diagnostic pop
 274
 275         _Unlock(const _Unlock&) = delete;
 276         _Unlock& operator=(const _Unlock&) = delete;
 277
 278         _Lock& _M_lock;
 279       };
 280
 281   public:
 282     condition_variable_any() : _M_mutex(std::make_shared<mutex>()) { }
 283     ~condition_variable_any() = default;
 284
 285     condition_variable_any(const condition_variable_any&) = delete;
 286     condition_variable_any& operator=(const condition_variable_any&) = delete;
 287
 288     void
 289     notify_one() noexcept
 290     {
 291       lock_guard<mutex> __lock(*_M_mutex);
 292       _M_cond.notify_one();
 293     }
 294
 295     void
 296     notify_all() noexcept
 297     {
 298       lock_guard<mutex> __lock(*_M_mutex);
 299       _M_cond.notify_all();
 300     }
 301
 302     template<typename _Lock>
 303       void
 304       wait(_Lock& __lock)
 305       {
 306         shared_ptr<mutex> __mutex = _M_mutex;
 307         unique_lock<mutex> __my_lock(*__mutex);
 308         _Unlock<_Lock> __unlock(__lock);
 309         // *__mutex must be unlocked before re-locking __lock so move
 310         // ownership of *__mutex lock to an object with shorter lifetime.
 311         unique_lock<mutex> __my_lock2(std::move(__my_lock));
 312         _M_cond.wait(__my_lock2);
 313       }
 314
 315
 316     template<typename _Lock, typename _Predicate>
 317       void
 318       wait(_Lock& __lock, _Predicate __p)
 319       {
 320         while (!__p())
 321           wait(__lock);
 322       }
 323
 324     template<typename _Lock, typename _Clock, typename _Duration>
 325       cv_status
 326       wait_until(_Lock& __lock,
 327                  const chrono::time_point<_Clock, _Duration>& __atime)
 328       {
 329         shared_ptr<mutex> __mutex = _M_mutex;
 330         unique_lock<mutex> __my_lock(*__mutex);
 331         _Unlock<_Lock> __unlock(__lock);
 332         // *__mutex must be unlocked before re-locking __lock so move
 333         // ownership of *__mutex lock to an object with shorter lifetime.
 334         unique_lock<mutex> __my_lock2(std::move(__my_lock));
 335         return _M_cond.wait_until(__my_lock2, __atime);
 336       }
 337
 338     template<typename _Lock, typename _Clock,
 339              typename _Duration, typename _Predicate>
 340       bool
 341       wait_until(_Lock& __lock,
 342                  const chrono::time_point<_Clock, _Duration>& __atime,
 343                  _Predicate __p)
 344       {
 345         while (!__p())
 346           if (wait_until(__lock, __atime) == cv_status::timeout)
 347             return __p();
 348         return true;
 349       }
 350
 351     template<typename _Lock, typename _Rep, typename _Period>
 352       cv_status
 353       wait_for(_Lock& __lock, const chrono::duration<_Rep, _Period>& __rtime)
 354       { return wait_until(__lock, __clock_t::now() + __rtime); }
 355
 356     template<typename _Lock, typename _Rep,
 357              typename _Period, typename _Predicate>
 358       bool
 359       wait_for(_Lock& __lock,
 360                const chrono::duration<_Rep, _Period>& __rtime, _Predicate __p)
 361       { return wait_until(__lock, __clock_t::now() + __rtime, std::move(__p)); }
 362
 363 #ifdef __cpp_lib_jthread
 364     template <class _Lock, class _Predicate>
 365     bool wait(_Lock& __lock,
 366               stop_token __stoken,
 367               _Predicate __p)
 368     {
 369       if (__stoken.stop_requested())
 370         {
 371           return __p();
 372         }
 373
 374       std::stop_callback __cb(__stoken, [this] { notify_all(); });
 375       shared_ptr<mutex> __mutex = _M_mutex;
 376       while (!__p())
 377         {
 378           unique_lock<mutex> __my_lock(*__mutex);
 379           if (__stoken.stop_requested())
 380             {
 381               return false;
 382             }
 383           // *__mutex must be unlocked before re-locking __lock so move
 384           // ownership of *__mutex lock to an object with shorter lifetime.
 385           _Unlock<_Lock> __unlock(__lock);
 386           unique_lock<mutex> __my_lock2(std::move(__my_lock));
 387           _M_cond.wait(__my_lock2);
 388         }
 389       return true;
 390     }
 391
 392     template <class _Lock, class _Clock, class _Duration, class _Predicate>
 393     bool wait_until(_Lock& __lock,
 394                     stop_token __stoken,
 395                     const chrono::time_point<_Clock, _Duration>& __abs_time,
 396                     _Predicate __p)
 397     {
 398       if (__stoken.stop_requested())
 399         {
 400           return __p();
 401         }
 402
 403       std::stop_callback __cb(__stoken, [this] { notify_all(); });
 404       shared_ptr<mutex> __mutex = _M_mutex;
 405       while (!__p())
 406         {
 407           bool __stop;
 408           {
 409             unique_lock<mutex> __my_lock(*__mutex);
 410             if (__stoken.stop_requested())
 411               {
 412                 return false;
 413               }
 414             _Unlock<_Lock> __u(__lock);
 415             unique_lock<mutex> __my_lock2(std::move(__my_lock));
 416             const auto __status = _M_cond.wait_until(__my_lock2, __abs_time);
 417             __stop = (__status == std::cv_status::timeout) || __stoken.stop_requested();
 418           }
 419           if (__stop)
 420             {
 421               return __p();
 422             }
 423         }
 424       return true;
 425     }
 426
 427     template <class _Lock, class _Rep, class _Period, class _Predicate>
 428     bool wait_for(_Lock& __lock,
 429                   stop_token __stoken,
 430                   const chrono::duration<_Rep, _Period>& __rel_time,
 431                   _Predicate __p)
 432     {
 433       auto __abst = std::chrono::steady_clock::now() + __rel_time;
 434       return wait_until(__lock,
 435                         std::move(__stoken),
 436                         __abst,
 437                         std::move(__p));
 438     }
 439 #endif
 440   };
 441
 442 _GLIBCXX_END_INLINE_ABI_NAMESPACE(_V2)
 443
 444   /// @} group condition_variables
 445 _GLIBCXX_END_NAMESPACE_VERSION
 446 } // namespace
 447
 448 #endif // _GLIBCXX_HAS_GTHREADS
 449 #endif // C++11
 450 #endif // _GLIBCXX_CONDITION_VARIABLE