libstdc++
mutex
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1// <mutex> -*- C++ -*-
2
3// Copyright (C) 2003-2020 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/mutex
26 * This is a Standard C++ Library header.
27 */
28
29#ifndef _GLIBCXX_MUTEX
30#define _GLIBCXX_MUTEX 1
31
32#pragma GCC system_header
33
34#if __cplusplus < 201103L
35# include <bits/c++0x_warning.h>
36#else
37
38#include <tuple>
39#include <chrono>
40#include <exception>
41#include <type_traits>
42#include <system_error>
43#include <bits/std_mutex.h>
44#include <bits/unique_lock.h>
45#if ! _GTHREAD_USE_MUTEX_TIMEDLOCK
46# include <condition_variable>
47# include <thread>
48#endif
49#ifndef _GLIBCXX_HAVE_TLS
50# include <bits/std_function.h>
51#endif
52
53namespace std _GLIBCXX_VISIBILITY(default)
54{
55_GLIBCXX_BEGIN_NAMESPACE_VERSION
56
57 /**
58 * @addtogroup mutexes
59 * @{
60 */
61
62#ifdef _GLIBCXX_HAS_GTHREADS
63
64 // Common base class for std::recursive_mutex and std::recursive_timed_mutex
65 class __recursive_mutex_base
66 {
67 protected:
68 typedef __gthread_recursive_mutex_t __native_type;
69
70 __recursive_mutex_base(const __recursive_mutex_base&) = delete;
71 __recursive_mutex_base& operator=(const __recursive_mutex_base&) = delete;
72
73#ifdef __GTHREAD_RECURSIVE_MUTEX_INIT
74 __native_type _M_mutex = __GTHREAD_RECURSIVE_MUTEX_INIT;
75
76 __recursive_mutex_base() = default;
77#else
78 __native_type _M_mutex;
79
80 __recursive_mutex_base()
81 {
82 // XXX EAGAIN, ENOMEM, EPERM, EBUSY(may), EINVAL(may)
83 __GTHREAD_RECURSIVE_MUTEX_INIT_FUNCTION(&_M_mutex);
84 }
85
86 ~__recursive_mutex_base()
87 { __gthread_recursive_mutex_destroy(&_M_mutex); }
88#endif
89 };
90
91 /// The standard recursive mutex type.
92 class recursive_mutex : private __recursive_mutex_base
93 {
94 public:
95 typedef __native_type* native_handle_type;
96
97 recursive_mutex() = default;
98 ~recursive_mutex() = default;
99
100 recursive_mutex(const recursive_mutex&) = delete;
101 recursive_mutex& operator=(const recursive_mutex&) = delete;
102
103 void
104 lock()
105 {
106 int __e = __gthread_recursive_mutex_lock(&_M_mutex);
107
108 // EINVAL, EAGAIN, EBUSY, EINVAL, EDEADLK(may)
109 if (__e)
110 __throw_system_error(__e);
111 }
112
113 bool
114 try_lock() noexcept
115 {
116 // XXX EINVAL, EAGAIN, EBUSY
117 return !__gthread_recursive_mutex_trylock(&_M_mutex);
118 }
119
120 void
121 unlock()
122 {
123 // XXX EINVAL, EAGAIN, EBUSY
124 __gthread_recursive_mutex_unlock(&_M_mutex);
125 }
126
127 native_handle_type
128 native_handle() noexcept
129 { return &_M_mutex; }
130 };
131
132#if _GTHREAD_USE_MUTEX_TIMEDLOCK
133 template<typename _Derived>
134 class __timed_mutex_impl
135 {
136 protected:
137 template<typename _Rep, typename _Period>
138 bool
139 _M_try_lock_for(const chrono::duration<_Rep, _Period>& __rtime)
140 {
141#if _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK
142 using __clock = chrono::steady_clock;
143#else
144 using __clock = chrono::system_clock;
145#endif
146
147 auto __rt = chrono::duration_cast<__clock::duration>(__rtime);
148 if (ratio_greater<__clock::period, _Period>())
149 ++__rt;
150 return _M_try_lock_until(__clock::now() + __rt);
151 }
152
153 template<typename _Duration>
154 bool
155 _M_try_lock_until(const chrono::time_point<chrono::system_clock,
156 _Duration>& __atime)
157 {
158 auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
159 auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
160
161 __gthread_time_t __ts = {
162 static_cast<std::time_t>(__s.time_since_epoch().count()),
163 static_cast<long>(__ns.count())
164 };
165
166 return static_cast<_Derived*>(this)->_M_timedlock(__ts);
167 }
168
169#ifdef _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK
170 template<typename _Duration>
171 bool
172 _M_try_lock_until(const chrono::time_point<chrono::steady_clock,
173 _Duration>& __atime)
174 {
175 auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
176 auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
177
178 __gthread_time_t __ts = {
179 static_cast<std::time_t>(__s.time_since_epoch().count()),
180 static_cast<long>(__ns.count())
181 };
182
183 return static_cast<_Derived*>(this)->_M_clocklock(CLOCK_MONOTONIC,
184 __ts);
185 }
186#endif
187
188 template<typename _Clock, typename _Duration>
189 bool
190 _M_try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime)
191 {
192#if __cplusplus > 201703L
193 static_assert(chrono::is_clock_v<_Clock>);
194#endif
195 // The user-supplied clock may not tick at the same rate as
196 // steady_clock, so we must loop in order to guarantee that
197 // the timeout has expired before returning false.
198 auto __now = _Clock::now();
199 do {
200 auto __rtime = __atime - __now;
201 if (_M_try_lock_for(__rtime))
202 return true;
203 __now = _Clock::now();
204 } while (__atime > __now);
205 return false;
206 }
207 };
208
209 /// The standard timed mutex type.
210 class timed_mutex
211 : private __mutex_base, public __timed_mutex_impl<timed_mutex>
212 {
213 public:
214 typedef __native_type* native_handle_type;
215
216 timed_mutex() = default;
217 ~timed_mutex() = default;
218
219 timed_mutex(const timed_mutex&) = delete;
220 timed_mutex& operator=(const timed_mutex&) = delete;
221
222 void
223 lock()
224 {
225 int __e = __gthread_mutex_lock(&_M_mutex);
226
227 // EINVAL, EAGAIN, EBUSY, EINVAL, EDEADLK(may)
228 if (__e)
229 __throw_system_error(__e);
230 }
231
232 bool
233 try_lock() noexcept
234 {
235 // XXX EINVAL, EAGAIN, EBUSY
236 return !__gthread_mutex_trylock(&_M_mutex);
237 }
238
239 template <class _Rep, class _Period>
240 bool
241 try_lock_for(const chrono::duration<_Rep, _Period>& __rtime)
242 { return _M_try_lock_for(__rtime); }
243
244 template <class _Clock, class _Duration>
245 bool
246 try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime)
247 { return _M_try_lock_until(__atime); }
248
249 void
250 unlock()
251 {
252 // XXX EINVAL, EAGAIN, EBUSY
253 __gthread_mutex_unlock(&_M_mutex);
254 }
255
256 native_handle_type
257 native_handle() noexcept
258 { return &_M_mutex; }
259
260 private:
261 friend class __timed_mutex_impl<timed_mutex>;
262
263 bool
264 _M_timedlock(const __gthread_time_t& __ts)
265 { return !__gthread_mutex_timedlock(&_M_mutex, &__ts); }
266
267#if _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK
268 bool
269 _M_clocklock(clockid_t clockid, const __gthread_time_t& __ts)
270 { return !pthread_mutex_clocklock(&_M_mutex, clockid, &__ts); }
271#endif
272 };
273
274 /// recursive_timed_mutex
275 class recursive_timed_mutex
276 : private __recursive_mutex_base,
277 public __timed_mutex_impl<recursive_timed_mutex>
278 {
279 public:
280 typedef __native_type* native_handle_type;
281
282 recursive_timed_mutex() = default;
283 ~recursive_timed_mutex() = default;
284
285 recursive_timed_mutex(const recursive_timed_mutex&) = delete;
286 recursive_timed_mutex& operator=(const recursive_timed_mutex&) = delete;
287
288 void
289 lock()
290 {
291 int __e = __gthread_recursive_mutex_lock(&_M_mutex);
292
293 // EINVAL, EAGAIN, EBUSY, EINVAL, EDEADLK(may)
294 if (__e)
295 __throw_system_error(__e);
296 }
297
298 bool
299 try_lock() noexcept
300 {
301 // XXX EINVAL, EAGAIN, EBUSY
302 return !__gthread_recursive_mutex_trylock(&_M_mutex);
303 }
304
305 template <class _Rep, class _Period>
306 bool
307 try_lock_for(const chrono::duration<_Rep, _Period>& __rtime)
308 { return _M_try_lock_for(__rtime); }
309
310 template <class _Clock, class _Duration>
311 bool
312 try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime)
313 { return _M_try_lock_until(__atime); }
314
315 void
316 unlock()
317 {
318 // XXX EINVAL, EAGAIN, EBUSY
319 __gthread_recursive_mutex_unlock(&_M_mutex);
320 }
321
322 native_handle_type
323 native_handle() noexcept
324 { return &_M_mutex; }
325
326 private:
327 friend class __timed_mutex_impl<recursive_timed_mutex>;
328
329 bool
330 _M_timedlock(const __gthread_time_t& __ts)
331 { return !__gthread_recursive_mutex_timedlock(&_M_mutex, &__ts); }
332
333#ifdef _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK
334 bool
335 _M_clocklock(clockid_t clockid, const __gthread_time_t& __ts)
336 { return !pthread_mutex_clocklock(&_M_mutex, clockid, &__ts); }
337#endif
338 };
339
340#else // !_GTHREAD_USE_MUTEX_TIMEDLOCK
341
342 /// timed_mutex
343 class timed_mutex
344 {
345 mutex _M_mut;
346 condition_variable _M_cv;
347 bool _M_locked = false;
348
349 public:
350
351 timed_mutex() = default;
352 ~timed_mutex() { __glibcxx_assert( !_M_locked ); }
353
354 timed_mutex(const timed_mutex&) = delete;
355 timed_mutex& operator=(const timed_mutex&) = delete;
356
357 void
358 lock()
359 {
360 unique_lock<mutex> __lk(_M_mut);
361 _M_cv.wait(__lk, [&]{ return !_M_locked; });
362 _M_locked = true;
363 }
364
365 bool
366 try_lock()
367 {
368 lock_guard<mutex> __lk(_M_mut);
369 if (_M_locked)
370 return false;
371 _M_locked = true;
372 return true;
373 }
374
375 template<typename _Rep, typename _Period>
376 bool
377 try_lock_for(const chrono::duration<_Rep, _Period>& __rtime)
378 {
379 unique_lock<mutex> __lk(_M_mut);
380 if (!_M_cv.wait_for(__lk, __rtime, [&]{ return !_M_locked; }))
381 return false;
382 _M_locked = true;
383 return true;
384 }
385
386 template<typename _Clock, typename _Duration>
387 bool
388 try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime)
389 {
390 unique_lock<mutex> __lk(_M_mut);
391 if (!_M_cv.wait_until(__lk, __atime, [&]{ return !_M_locked; }))
392 return false;
393 _M_locked = true;
394 return true;
395 }
396
397 void
398 unlock()
399 {
400 lock_guard<mutex> __lk(_M_mut);
401 __glibcxx_assert( _M_locked );
402 _M_locked = false;
403 _M_cv.notify_one();
404 }
405 };
406
407 /// recursive_timed_mutex
408 class recursive_timed_mutex
409 {
410 mutex _M_mut;
411 condition_variable _M_cv;
412 thread::id _M_owner;
413 unsigned _M_count = 0;
414
415 // Predicate type that tests whether the current thread can lock a mutex.
416 struct _Can_lock
417 {
418 // Returns true if the mutex is unlocked or is locked by _M_caller.
419 bool
420 operator()() const noexcept
421 { return _M_mx->_M_count == 0 || _M_mx->_M_owner == _M_caller; }
422
423 const recursive_timed_mutex* _M_mx;
424 thread::id _M_caller;
425 };
426
427 public:
428
429 recursive_timed_mutex() = default;
430 ~recursive_timed_mutex() { __glibcxx_assert( _M_count == 0 ); }
431
432 recursive_timed_mutex(const recursive_timed_mutex&) = delete;
433 recursive_timed_mutex& operator=(const recursive_timed_mutex&) = delete;
434
435 void
436 lock()
437 {
438 auto __id = this_thread::get_id();
439 _Can_lock __can_lock{this, __id};
440 unique_lock<mutex> __lk(_M_mut);
441 _M_cv.wait(__lk, __can_lock);
442 if (_M_count == -1u)
443 __throw_system_error(EAGAIN); // [thread.timedmutex.recursive]/3
444 _M_owner = __id;
445 ++_M_count;
446 }
447
448 bool
449 try_lock()
450 {
451 auto __id = this_thread::get_id();
452 _Can_lock __can_lock{this, __id};
453 lock_guard<mutex> __lk(_M_mut);
454 if (!__can_lock())
455 return false;
456 if (_M_count == -1u)
457 return false;
458 _M_owner = __id;
459 ++_M_count;
460 return true;
461 }
462
463 template<typename _Rep, typename _Period>
464 bool
465 try_lock_for(const chrono::duration<_Rep, _Period>& __rtime)
466 {
467 auto __id = this_thread::get_id();
468 _Can_lock __can_lock{this, __id};
469 unique_lock<mutex> __lk(_M_mut);
470 if (!_M_cv.wait_for(__lk, __rtime, __can_lock))
471 return false;
472 if (_M_count == -1u)
473 return false;
474 _M_owner = __id;
475 ++_M_count;
476 return true;
477 }
478
479 template<typename _Clock, typename _Duration>
480 bool
481 try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime)
482 {
483 auto __id = this_thread::get_id();
484 _Can_lock __can_lock{this, __id};
485 unique_lock<mutex> __lk(_M_mut);
486 if (!_M_cv.wait_until(__lk, __atime, __can_lock))
487 return false;
488 if (_M_count == -1u)
489 return false;
490 _M_owner = __id;
491 ++_M_count;
492 return true;
493 }
494
495 void
496 unlock()
497 {
498 lock_guard<mutex> __lk(_M_mut);
499 __glibcxx_assert( _M_owner == this_thread::get_id() );
500 __glibcxx_assert( _M_count > 0 );
501 if (--_M_count == 0)
502 {
503 _M_owner = {};
504 _M_cv.notify_one();
505 }
506 }
507 };
508
509#endif
510#endif // _GLIBCXX_HAS_GTHREADS
511
512 /// @cond undocumented
513 template<typename _Lock>
514 inline unique_lock<_Lock>
515 __try_to_lock(_Lock& __l)
516 { return unique_lock<_Lock>{__l, try_to_lock}; }
517
518 template<int _Idx, bool _Continue = true>
519 struct __try_lock_impl
520 {
521 template<typename... _Lock>
522 static void
523 __do_try_lock(tuple<_Lock&...>& __locks, int& __idx)
524 {
525 __idx = _Idx;
526 auto __lock = std::__try_to_lock(std::get<_Idx>(__locks));
527 if (__lock.owns_lock())
528 {
529 constexpr bool __cont = _Idx + 2 < sizeof...(_Lock);
530 using __try_locker = __try_lock_impl<_Idx + 1, __cont>;
531 __try_locker::__do_try_lock(__locks, __idx);
532 if (__idx == -1)
533 __lock.release();
534 }
535 }
536 };
537
538 template<int _Idx>
539 struct __try_lock_impl<_Idx, false>
540 {
541 template<typename... _Lock>
542 static void
543 __do_try_lock(tuple<_Lock&...>& __locks, int& __idx)
544 {
545 __idx = _Idx;
546 auto __lock = std::__try_to_lock(std::get<_Idx>(__locks));
547 if (__lock.owns_lock())
548 {
549 __idx = -1;
550 __lock.release();
551 }
552 }
553 };
554 /// @endcond
555
556 /** @brief Generic try_lock.
557 * @param __l1 Meets Lockable requirements (try_lock() may throw).
558 * @param __l2 Meets Lockable requirements (try_lock() may throw).
559 * @param __l3 Meets Lockable requirements (try_lock() may throw).
560 * @return Returns -1 if all try_lock() calls return true. Otherwise returns
561 * a 0-based index corresponding to the argument that returned false.
562 * @post Either all arguments are locked, or none will be.
563 *
564 * Sequentially calls try_lock() on each argument.
565 */
566 template<typename _Lock1, typename _Lock2, typename... _Lock3>
567 int
568 try_lock(_Lock1& __l1, _Lock2& __l2, _Lock3&... __l3)
569 {
570 int __idx;
571 auto __locks = std::tie(__l1, __l2, __l3...);
572 __try_lock_impl<0>::__do_try_lock(__locks, __idx);
573 return __idx;
574 }
575
576 /** @brief Generic lock.
577 * @param __l1 Meets Lockable requirements (try_lock() may throw).
578 * @param __l2 Meets Lockable requirements (try_lock() may throw).
579 * @param __l3 Meets Lockable requirements (try_lock() may throw).
580 * @throw An exception thrown by an argument's lock() or try_lock() member.
581 * @post All arguments are locked.
582 *
583 * All arguments are locked via a sequence of calls to lock(), try_lock()
584 * and unlock(). If the call exits via an exception any locks that were
585 * obtained will be released.
586 */
587 template<typename _L1, typename _L2, typename... _L3>
588 void
589 lock(_L1& __l1, _L2& __l2, _L3&... __l3)
590 {
591 while (true)
592 {
593 using __try_locker = __try_lock_impl<0, sizeof...(_L3) != 0>;
594 unique_lock<_L1> __first(__l1);
595 int __idx;
596 auto __locks = std::tie(__l2, __l3...);
597 __try_locker::__do_try_lock(__locks, __idx);
598 if (__idx == -1)
599 {
600 __first.release();
601 return;
602 }
603 }
604 }
605
606#if __cplusplus >= 201703L
607#define __cpp_lib_scoped_lock 201703
608 /** @brief A scoped lock type for multiple lockable objects.
609 *
610 * A scoped_lock controls mutex ownership within a scope, releasing
611 * ownership in the destructor.
612 */
613 template<typename... _MutexTypes>
614 class scoped_lock
615 {
616 public:
617 explicit scoped_lock(_MutexTypes&... __m) : _M_devices(std::tie(__m...))
618 { std::lock(__m...); }
619
620 explicit scoped_lock(adopt_lock_t, _MutexTypes&... __m) noexcept
621 : _M_devices(std::tie(__m...))
622 { } // calling thread owns mutex
623
624 ~scoped_lock()
625 { std::apply([](auto&... __m) { (__m.unlock(), ...); }, _M_devices); }
626
627 scoped_lock(const scoped_lock&) = delete;
628 scoped_lock& operator=(const scoped_lock&) = delete;
629
630 private:
631 tuple<_MutexTypes&...> _M_devices;
632 };
633
634 template<>
635 class scoped_lock<>
636 {
637 public:
638 explicit scoped_lock() = default;
639 explicit scoped_lock(adopt_lock_t) noexcept { }
640 ~scoped_lock() = default;
641
642 scoped_lock(const scoped_lock&) = delete;
643 scoped_lock& operator=(const scoped_lock&) = delete;
644 };
645
646 template<typename _Mutex>
647 class scoped_lock<_Mutex>
648 {
649 public:
650 using mutex_type = _Mutex;
651
652 explicit scoped_lock(mutex_type& __m) : _M_device(__m)
653 { _M_device.lock(); }
654
655 explicit scoped_lock(adopt_lock_t, mutex_type& __m) noexcept
656 : _M_device(__m)
657 { } // calling thread owns mutex
658
659 ~scoped_lock()
660 { _M_device.unlock(); }
661
662 scoped_lock(const scoped_lock&) = delete;
663 scoped_lock& operator=(const scoped_lock&) = delete;
664
665 private:
666 mutex_type& _M_device;
667 };
668#endif // C++17
669
670#ifdef _GLIBCXX_HAS_GTHREADS
671 /// Flag type used by std::call_once
672 struct once_flag
673 {
674 private:
675 typedef __gthread_once_t __native_type;
676 __native_type _M_once = __GTHREAD_ONCE_INIT;
677
678 public:
679 /// Constructor
680 constexpr once_flag() noexcept = default;
681
682 /// Deleted copy constructor
683 once_flag(const once_flag&) = delete;
684 /// Deleted assignment operator
685 once_flag& operator=(const once_flag&) = delete;
686
687 template<typename _Callable, typename... _Args>
688 friend void
689 call_once(once_flag& __once, _Callable&& __f, _Args&&... __args);
690 };
691
692 /// @cond undocumented
693#ifdef _GLIBCXX_HAVE_TLS
694 extern __thread void* __once_callable;
695 extern __thread void (*__once_call)();
696#else
697 extern function<void()> __once_functor;
698
699 extern void
700 __set_once_functor_lock_ptr(unique_lock<mutex>*);
701
702 extern mutex&
703 __get_once_mutex();
704#endif
705
706 extern "C" void __once_proxy(void);
707 /// @endcond
708
709 /// Invoke a callable and synchronize with other calls using the same flag
710 template<typename _Callable, typename... _Args>
711 void
712 call_once(once_flag& __once, _Callable&& __f, _Args&&... __args)
713 {
714 // _GLIBCXX_RESOLVE_LIB_DEFECTS
715 // 2442. call_once() shouldn't DECAY_COPY()
716 auto __callable = [&] {
717 std::__invoke(std::forward<_Callable>(__f),
718 std::forward<_Args>(__args)...);
719 };
720#ifdef _GLIBCXX_HAVE_TLS
721 __once_callable = std::__addressof(__callable); // NOLINT: PR 82481
722 __once_call = []{ (*(decltype(__callable)*)__once_callable)(); };
723#else
724 unique_lock<mutex> __functor_lock(__get_once_mutex());
725 __once_functor = __callable;
726 __set_once_functor_lock_ptr(&__functor_lock);
727#endif
728
729 int __e = __gthread_once(&__once._M_once, &__once_proxy);
730
731#ifndef _GLIBCXX_HAVE_TLS
732 if (__functor_lock)
733 __set_once_functor_lock_ptr(0);
734#endif
735
736 if (__e)
737 __throw_system_error(__e);
738 }
739#endif // _GLIBCXX_HAS_GTHREADS
740
741 /// @} group mutexes
742_GLIBCXX_END_NAMESPACE_VERSION
743} // namespace
744
745#endif // C++11
746
747#endif // _GLIBCXX_MUTEX