libstdc++
condition_variable
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1 // <condition_variable> -*- C++ -*-
2 
3 // Copyright (C) 2008-2020 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 <chrono>
39 
40 #include <bits/std_mutex.h>
41 #include <bits/unique_lock.h>
42 #include <ext/concurrence.h>
43 #include <bits/alloc_traits.h>
44 #include <bits/allocator.h>
45 #include <bits/unique_ptr.h>
46 #include <bits/shared_ptr.h>
47 #include <bits/cxxabi_forced.h>
48 
49 #if __cplusplus > 201703L
50 #define __cpp_lib_jthread 201907L
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
73  {
76 #ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
77  using __clock_t = steady_clock;
78 #else
79  using __clock_t = system_clock;
80 #endif
81  typedef __gthread_cond_t __native_type;
82 
83 #ifdef __GTHREAD_COND_INIT
84  __native_type _M_cond = __GTHREAD_COND_INIT;
85 #else
86  __native_type _M_cond;
87 #endif
88 
89  public:
90  typedef __native_type* native_handle_type;
91 
92  condition_variable() noexcept;
93  ~condition_variable() noexcept;
94 
95  condition_variable(const condition_variable&) = delete;
96  condition_variable& operator=(const condition_variable&) = delete;
97 
98  void
99  notify_one() noexcept;
100 
101  void
102  notify_all() noexcept;
103 
104  void
105  wait(unique_lock<mutex>& __lock) noexcept;
106 
107  template<typename _Predicate>
108  void
109  wait(unique_lock<mutex>& __lock, _Predicate __p)
110  {
111  while (!__p())
112  wait(__lock);
113  }
114 
115 #ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
116  template<typename _Duration>
117  cv_status
118  wait_until(unique_lock<mutex>& __lock,
120  { return __wait_until_impl(__lock, __atime); }
121 #endif
122 
123  template<typename _Duration>
124  cv_status
125  wait_until(unique_lock<mutex>& __lock,
127  { return __wait_until_impl(__lock, __atime); }
128 
129  template<typename _Clock, typename _Duration>
130  cv_status
131  wait_until(unique_lock<mutex>& __lock,
133  {
134 #if __cplusplus > 201703L
135  static_assert(chrono::is_clock_v<_Clock>);
136 #endif
137  const typename _Clock::time_point __c_entry = _Clock::now();
138  const __clock_t::time_point __s_entry = __clock_t::now();
139  const auto __delta = __atime - __c_entry;
140  const auto __s_atime = __s_entry + __delta;
141 
142  if (__wait_until_impl(__lock, __s_atime) == cv_status::no_timeout)
143  return cv_status::no_timeout;
144  // We got a timeout when measured against __clock_t but
145  // we need to check against the caller-supplied clock
146  // to tell whether we should return a timeout.
147  if (_Clock::now() < __atime)
148  return cv_status::no_timeout;
149  return cv_status::timeout;
150  }
151 
152  template<typename _Clock, typename _Duration, typename _Predicate>
153  bool
154  wait_until(unique_lock<mutex>& __lock,
156  _Predicate __p)
157  {
158  while (!__p())
159  if (wait_until(__lock, __atime) == cv_status::timeout)
160  return __p();
161  return true;
162  }
163 
164  template<typename _Rep, typename _Period>
165  cv_status
166  wait_for(unique_lock<mutex>& __lock,
167  const chrono::duration<_Rep, _Period>& __rtime)
168  {
169  using __dur = typename steady_clock::duration;
170  auto __reltime = chrono::duration_cast<__dur>(__rtime);
171  if (__reltime < __rtime)
172  ++__reltime;
173  return wait_until(__lock, steady_clock::now() + __reltime);
174  }
175 
176  template<typename _Rep, typename _Period, typename _Predicate>
177  bool
178  wait_for(unique_lock<mutex>& __lock,
179  const chrono::duration<_Rep, _Period>& __rtime,
180  _Predicate __p)
181  {
182  using __dur = typename steady_clock::duration;
183  auto __reltime = chrono::duration_cast<__dur>(__rtime);
184  if (__reltime < __rtime)
185  ++__reltime;
186  return wait_until(__lock, steady_clock::now() + __reltime,
187  std::move(__p));
188  }
189 
190  native_handle_type
191  native_handle()
192  { return &_M_cond; }
193 
194  private:
195 #ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
196  template<typename _Dur>
197  cv_status
198  __wait_until_impl(unique_lock<mutex>& __lock,
200  {
201  auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
202  auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
203 
204  __gthread_time_t __ts =
205  {
206  static_cast<std::time_t>(__s.time_since_epoch().count()),
207  static_cast<long>(__ns.count())
208  };
209 
210  pthread_cond_clockwait(&_M_cond, __lock.mutex()->native_handle(),
211  CLOCK_MONOTONIC,
212  &__ts);
213 
214  return (steady_clock::now() < __atime
215  ? cv_status::no_timeout : cv_status::timeout);
216  }
217 #endif
218 
219  template<typename _Dur>
220  cv_status
221  __wait_until_impl(unique_lock<mutex>& __lock,
223  {
224  auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
225  auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
226 
227  __gthread_time_t __ts =
228  {
229  static_cast<std::time_t>(__s.time_since_epoch().count()),
230  static_cast<long>(__ns.count())
231  };
232 
233  __gthread_cond_timedwait(&_M_cond, __lock.mutex()->native_handle(),
234  &__ts);
235 
236  return (system_clock::now() < __atime
237  ? cv_status::no_timeout : cv_status::timeout);
238  }
239  };
240 
241  void
242  notify_all_at_thread_exit(condition_variable&, unique_lock<mutex>);
243 
244  struct __at_thread_exit_elt
245  {
246  __at_thread_exit_elt* _M_next;
247  void (*_M_cb)(void*);
248  };
249 
250  inline namespace _V2 {
251 
252  /// condition_variable_any
253  // Like above, but mutex is not required to have try_lock.
255  {
256 #ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
258 #else
260 #endif
261  condition_variable _M_cond;
262  shared_ptr<mutex> _M_mutex;
263 
264  // scoped unlock - unlocks in ctor, re-locks in dtor
265  template<typename _Lock>
266  struct _Unlock
267  {
268  explicit _Unlock(_Lock& __lk) : _M_lock(__lk) { __lk.unlock(); }
269 
270  ~_Unlock() noexcept(false)
271  {
272  if (uncaught_exception())
273  {
274  __try
275  { _M_lock.lock(); }
276  __catch(const __cxxabiv1::__forced_unwind&)
277  { __throw_exception_again; }
278  __catch(...)
279  { }
280  }
281  else
282  _M_lock.lock();
283  }
284 
285  _Unlock(const _Unlock&) = delete;
286  _Unlock& operator=(const _Unlock&) = delete;
287 
288  _Lock& _M_lock;
289  };
290 
291  public:
292  condition_variable_any() : _M_mutex(std::make_shared<mutex>()) { }
293  ~condition_variable_any() = default;
294 
296  condition_variable_any& operator=(const condition_variable_any&) = delete;
297 
298  void
299  notify_one() noexcept
300  {
301  lock_guard<mutex> __lock(*_M_mutex);
302  _M_cond.notify_one();
303  }
304 
305  void
306  notify_all() noexcept
307  {
308  lock_guard<mutex> __lock(*_M_mutex);
309  _M_cond.notify_all();
310  }
311 
312  template<typename _Lock>
313  void
314  wait(_Lock& __lock)
315  {
316  shared_ptr<mutex> __mutex = _M_mutex;
317  unique_lock<mutex> __my_lock(*__mutex);
318  _Unlock<_Lock> __unlock(__lock);
319  // *__mutex must be unlocked before re-locking __lock so move
320  // ownership of *__mutex lock to an object with shorter lifetime.
321  unique_lock<mutex> __my_lock2(std::move(__my_lock));
322  _M_cond.wait(__my_lock2);
323  }
324 
325 
326  template<typename _Lock, typename _Predicate>
327  void
328  wait(_Lock& __lock, _Predicate __p)
329  {
330  while (!__p())
331  wait(__lock);
332  }
333 
334  template<typename _Lock, typename _Clock, typename _Duration>
335  cv_status
336  wait_until(_Lock& __lock,
338  {
339  shared_ptr<mutex> __mutex = _M_mutex;
340  unique_lock<mutex> __my_lock(*__mutex);
341  _Unlock<_Lock> __unlock(__lock);
342  // *__mutex must be unlocked before re-locking __lock so move
343  // ownership of *__mutex lock to an object with shorter lifetime.
344  unique_lock<mutex> __my_lock2(std::move(__my_lock));
345  return _M_cond.wait_until(__my_lock2, __atime);
346  }
347 
348  template<typename _Lock, typename _Clock,
349  typename _Duration, typename _Predicate>
350  bool
351  wait_until(_Lock& __lock,
353  _Predicate __p)
354  {
355  while (!__p())
356  if (wait_until(__lock, __atime) == cv_status::timeout)
357  return __p();
358  return true;
359  }
360 
361  template<typename _Lock, typename _Rep, typename _Period>
362  cv_status
363  wait_for(_Lock& __lock, const chrono::duration<_Rep, _Period>& __rtime)
364  { return wait_until(__lock, __clock_t::now() + __rtime); }
365 
366  template<typename _Lock, typename _Rep,
367  typename _Period, typename _Predicate>
368  bool
369  wait_for(_Lock& __lock,
370  const chrono::duration<_Rep, _Period>& __rtime, _Predicate __p)
371  { return wait_until(__lock, __clock_t::now() + __rtime, std::move(__p)); }
372 
373 #ifdef __cpp_lib_jthread
374  template <class _Lock, class _Predicate>
375  bool wait(_Lock& __lock,
376  stop_token __stoken,
377  _Predicate __p)
378  {
379  if (__stoken.stop_requested())
380  {
381  return __p();
382  }
383 
384  std::stop_callback __cb(__stoken, [this] { notify_all(); });
385  shared_ptr<mutex> __mutex = _M_mutex;
386  while (!__p())
387  {
388  unique_lock<mutex> __my_lock(*__mutex);
389  if (__stoken.stop_requested())
390  {
391  return false;
392  }
393  // *__mutex must be unlocked before re-locking __lock so move
394  // ownership of *__mutex lock to an object with shorter lifetime.
395  _Unlock<_Lock> __unlock(__lock);
396  unique_lock<mutex> __my_lock2(std::move(__my_lock));
397  _M_cond.wait(__my_lock2);
398  }
399  return true;
400  }
401 
402  template <class _Lock, class _Clock, class _Duration, class _Predicate>
403  bool wait_until(_Lock& __lock,
404  stop_token __stoken,
405  const chrono::time_point<_Clock, _Duration>& __abs_time,
406  _Predicate __p)
407  {
408  if (__stoken.stop_requested())
409  {
410  return __p();
411  }
412 
413  std::stop_callback __cb(__stoken, [this] { notify_all(); });
414  shared_ptr<mutex> __mutex = _M_mutex;
415  while (!__p())
416  {
417  bool __stop;
418  {
419  unique_lock<mutex> __my_lock(*__mutex);
420  if (__stoken.stop_requested())
421  {
422  return false;
423  }
424  _Unlock<_Lock> __u(__lock);
425  unique_lock<mutex> __my_lock2(std::move(__my_lock));
426  const auto __status = _M_cond.wait_until(__my_lock2, __abs_time);
427  __stop = (__status == std::cv_status::timeout) || __stoken.stop_requested();
428  }
429  if (__stop)
430  {
431  return __p();
432  }
433  }
434  return true;
435  }
436 
437  template <class _Lock, class _Rep, class _Period, class _Predicate>
438  bool wait_for(_Lock& __lock,
439  stop_token __stoken,
440  const chrono::duration<_Rep, _Period>& __rel_time,
441  _Predicate __p)
442  {
443  auto __abst = std::chrono::steady_clock::now() + __rel_time;
444  return wait_until(__lock,
445  std::move(__stoken),
446  __abst,
447  std::move(__p));
448  }
449 #endif
450  };
451 
452  } // end inline namespace
453 
454  // @} group condition_variables
455 _GLIBCXX_END_NAMESPACE_VERSION
456 } // namespace
457 
458 #endif // _GLIBCXX_HAS_GTHREADS
459 #endif // C++11
460 #endif // _GLIBCXX_CONDITION_VARIABLE
std::shared_ptr
A smart pointer with reference-counted copy semantics.
Definition: bits/shared_ptr.h:121
alloc_traits.h
unique_lock.h
std::chrono::_V2::steady_clock
Monotonic clock.
Definition: chrono:1028
std::chrono::_V2::system_clock
System clock.
Definition: chrono:988
std::lock_guard
A simple scoped lock type.
Definition: std_mutex.h:153
std::uncaught_exception
bool uncaught_exception() noexcept
cxxabi_forced.h
std
ISO C++ entities toplevel namespace is std.
std::chrono::time_point
time_point
Definition: chrono:74
std::_V2::condition_variable_any
condition_variable_any
Definition: condition_variable:254
std::unique_lock
A movable scoped lock type.
Definition: unique_lock.h:56
std_mutex.h
allocator.h
stop_token
std::cv_status
cv_status
cv_status
Definition: condition_variable:69
unique_ptr.h
chrono
std::condition_variable
condition_variable
Definition: condition_variable:72
concurrence.h
c++0x_warning.h
std::chrono::duration
duration
Definition: chrono:71
__cxxabiv1::__forced_unwind
Thrown as part of forced unwinding.
Definition: cxxabi_forced.h:48
std::move
constexpr std::remove_reference< _Tp >::type && move(_Tp &&__t) noexcept
Convert a value to an rvalue.
Definition: move.h:101