libcxx/include/shared_mutex

   1 // -*- C++ -*-
   2 //===------------------------ shared_mutex --------------------------------===//
   3 //
   4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   5 // See https://llvm.org/LICENSE.txt for license information.
   6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 #ifndef _LIBCPP_SHARED_MUTEX
  11 #define _LIBCPP_SHARED_MUTEX
  12
  13 /*
  14     shared_mutex synopsis
  15
  16 // C++1y
  17
  18 namespace std
  19 {
  20
  21 class shared_mutex      // C++17
  22 {
  23 public:
  24     shared_mutex();
  25     ~shared_mutex();
  26
  27     shared_mutex(const shared_mutex&) = delete;
  28     shared_mutex& operator=(const shared_mutex&) = delete;
  29
  30     // Exclusive ownership
  31     void lock(); // blocking
  32     bool try_lock();
  33     void unlock();
  34
  35     // Shared ownership
  36     void lock_shared(); // blocking
  37     bool try_lock_shared();
  38     void unlock_shared();
  39
  40     typedef implementation-defined native_handle_type; // See 30.2.3
  41     native_handle_type native_handle(); // See 30.2.3
  42 };
  43
  44 class shared_timed_mutex
  45 {
  46 public:
  47     shared_timed_mutex();
  48     ~shared_timed_mutex();
  49
  50     shared_timed_mutex(const shared_timed_mutex&) = delete;
  51     shared_timed_mutex& operator=(const shared_timed_mutex&) = delete;
  52
  53     // Exclusive ownership
  54     void lock(); // blocking
  55     bool try_lock();
  56     template <class Rep, class Period>
  57         bool try_lock_for(const chrono::duration<Rep, Period>& rel_time);
  58     template <class Clock, class Duration>
  59         bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time);
  60     void unlock();
  61
  62     // Shared ownership
  63     void lock_shared(); // blocking
  64     bool try_lock_shared();
  65     template <class Rep, class Period>
  66         bool
  67         try_lock_shared_for(const chrono::duration<Rep, Period>& rel_time);
  68     template <class Clock, class Duration>
  69         bool
  70         try_lock_shared_until(const chrono::time_point<Clock, Duration>& abs_time);
  71     void unlock_shared();
  72 };
  73
  74 template <class Mutex>
  75 class shared_lock
  76 {
  77 public:
  78     typedef Mutex mutex_type;
  79
  80     // Shared locking
  81     shared_lock() noexcept;
  82     explicit shared_lock(mutex_type& m); // blocking
  83     shared_lock(mutex_type& m, defer_lock_t) noexcept;
  84     shared_lock(mutex_type& m, try_to_lock_t);
  85     shared_lock(mutex_type& m, adopt_lock_t);
  86     template <class Clock, class Duration>
  87         shared_lock(mutex_type& m,
  88                     const chrono::time_point<Clock, Duration>& abs_time);
  89     template <class Rep, class Period>
  90         shared_lock(mutex_type& m,
  91                     const chrono::duration<Rep, Period>& rel_time);
  92     ~shared_lock();
  93
  94     shared_lock(shared_lock const&) = delete;
  95     shared_lock& operator=(shared_lock const&) = delete;
  96
  97     shared_lock(shared_lock&& u) noexcept;
  98     shared_lock& operator=(shared_lock&& u) noexcept;
  99
 100     void lock(); // blocking
 101     bool try_lock();
 102     template <class Rep, class Period>
 103         bool try_lock_for(const chrono::duration<Rep, Period>& rel_time);
 104     template <class Clock, class Duration>
 105         bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time);
 106     void unlock();
 107
 108     // Setters
 109     void swap(shared_lock& u) noexcept;
 110     mutex_type* release() noexcept;
 111
 112     // Getters
 113     bool owns_lock() const noexcept;
 114     explicit operator bool () const noexcept;
 115     mutex_type* mutex() const noexcept;
 116 };
 117
 118 template <class Mutex>
 119     void swap(shared_lock<Mutex>& x, shared_lock<Mutex>& y) noexcept;
 120
 121 }  // std
 122
 123 */
 124
 125 #include <__availability>
 126 #include <__config>
 127 #include <version>
 128
 129 _LIBCPP_PUSH_MACROS
 130 #include <__undef_macros>
 131
 132
 133 #if _LIBCPP_STD_VER > 11 || defined(_LIBCPP_BUILDING_LIBRARY)
 134
 135 #include <__mutex_base>
 136
 137 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 138 #pragma GCC system_header
 139 #endif
 140
 141 #ifdef _LIBCPP_HAS_NO_THREADS
 142 #error <shared_mutex> is not supported on this single threaded system
 143 #else // !_LIBCPP_HAS_NO_THREADS
 144
 145 _LIBCPP_BEGIN_NAMESPACE_STD
 146
 147 struct _LIBCPP_TYPE_VIS _LIBCPP_AVAILABILITY_SHARED_MUTEX _LIBCPP_THREAD_SAFETY_ANNOTATION(capability("shared_mutex"))
 148 __shared_mutex_base
 149 {
 150     mutex               __mut_;
 151     condition_variable  __gate1_;
 152     condition_variable  __gate2_;
 153     unsigned            __state_;
 154
 155     static const unsigned __write_entered_ = 1U << (sizeof(unsigned)*__CHAR_BIT__ - 1);
 156     static const unsigned __n_readers_ = ~__write_entered_;
 157
 158     __shared_mutex_base();
 159     _LIBCPP_INLINE_VISIBILITY ~__shared_mutex_base() = default;
 160
 161     __shared_mutex_base(const __shared_mutex_base&) = delete;
 162     __shared_mutex_base& operator=(const __shared_mutex_base&) = delete;
 163
 164     // Exclusive ownership
 165     void lock() _LIBCPP_THREAD_SAFETY_ANNOTATION(acquire_capability()); // blocking
 166     bool try_lock() _LIBCPP_THREAD_SAFETY_ANNOTATION(try_acquire_capability(true));
 167     void unlock() _LIBCPP_THREAD_SAFETY_ANNOTATION(release_capability());
 168
 169     // Shared ownership
 170     void lock_shared() _LIBCPP_THREAD_SAFETY_ANNOTATION(acquire_shared_capability()); // blocking
 171     bool try_lock_shared() _LIBCPP_THREAD_SAFETY_ANNOTATION(try_acquire_shared_capability(true));
 172     void unlock_shared() _LIBCPP_THREAD_SAFETY_ANNOTATION(release_shared_capability());
 173
 174 //     typedef implementation-defined native_handle_type; // See 30.2.3
 175 //     native_handle_type native_handle(); // See 30.2.3
 176 };
 177
 178
 179 #if _LIBCPP_STD_VER > 14
 180 class _LIBCPP_TYPE_VIS _LIBCPP_AVAILABILITY_SHARED_MUTEX shared_mutex
 181 {
 182     __shared_mutex_base __base;
 183 public:
 184     _LIBCPP_INLINE_VISIBILITY shared_mutex() : __base() {}
 185     _LIBCPP_INLINE_VISIBILITY ~shared_mutex() = default;
 186
 187     shared_mutex(const shared_mutex&) = delete;
 188     shared_mutex& operator=(const shared_mutex&) = delete;
 189
 190     // Exclusive ownership
 191     _LIBCPP_INLINE_VISIBILITY void lock()     { return __base.lock(); }
 192     _LIBCPP_INLINE_VISIBILITY bool try_lock() { return __base.try_lock(); }
 193     _LIBCPP_INLINE_VISIBILITY void unlock()   { return __base.unlock(); }
 194
 195     // Shared ownership
 196     _LIBCPP_INLINE_VISIBILITY void lock_shared()     { return __base.lock_shared(); }
 197     _LIBCPP_INLINE_VISIBILITY bool try_lock_shared() { return __base.try_lock_shared(); }
 198     _LIBCPP_INLINE_VISIBILITY void unlock_shared()   { return __base.unlock_shared(); }
 199
 200 //     typedef __shared_mutex_base::native_handle_type native_handle_type;
 201 //     _LIBCPP_INLINE_VISIBILITY native_handle_type native_handle() { return __base::unlock_shared(); }
 202 };
 203 #endif
 204
 205
 206 class _LIBCPP_TYPE_VIS _LIBCPP_AVAILABILITY_SHARED_MUTEX shared_timed_mutex
 207 {
 208     __shared_mutex_base __base;
 209 public:
 210     shared_timed_mutex();
 211     _LIBCPP_INLINE_VISIBILITY ~shared_timed_mutex() = default;
 212
 213     shared_timed_mutex(const shared_timed_mutex&) = delete;
 214     shared_timed_mutex& operator=(const shared_timed_mutex&) = delete;
 215
 216     // Exclusive ownership
 217     void lock();
 218     bool try_lock();
 219     template <class _Rep, class _Period>
 220         _LIBCPP_INLINE_VISIBILITY
 221         bool
 222         try_lock_for(const chrono::duration<_Rep, _Period>& __rel_time)
 223         {
 224             return try_lock_until(chrono::steady_clock::now() + __rel_time);
 225         }
 226     template <class _Clock, class _Duration>
 227         _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
 228         bool
 229         try_lock_until(const chrono::time_point<_Clock, _Duration>& __abs_time);
 230     void unlock();
 231
 232     // Shared ownership
 233     void lock_shared();
 234     bool try_lock_shared();
 235     template <class _Rep, class _Period>
 236         _LIBCPP_INLINE_VISIBILITY
 237         bool
 238         try_lock_shared_for(const chrono::duration<_Rep, _Period>& __rel_time)
 239         {
 240             return try_lock_shared_until(chrono::steady_clock::now() + __rel_time);
 241         }
 242     template <class _Clock, class _Duration>
 243         _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
 244         bool
 245         try_lock_shared_until(const chrono::time_point<_Clock, _Duration>& __abs_time);
 246     void unlock_shared();
 247 };
 248
 249 template <class _Clock, class _Duration>
 250 bool
 251 shared_timed_mutex::try_lock_until(
 252                         const chrono::time_point<_Clock, _Duration>& __abs_time)
 253 {
 254     unique_lock<mutex> __lk(__base.__mut_);
 255     if (__base.__state_ & __base.__write_entered_)
 256     {
 257         while (true)
 258         {
 259             cv_status __status = __base.__gate1_.wait_until(__lk, __abs_time);
 260             if ((__base.__state_ & __base.__write_entered_) == 0)
 261                 break;
 262             if (__status == cv_status::timeout)
 263                 return false;
 264         }
 265     }
 266     __base.__state_ |= __base.__write_entered_;
 267     if (__base.__state_ & __base.__n_readers_)
 268     {
 269         while (true)
 270         {
 271             cv_status __status = __base.__gate2_.wait_until(__lk, __abs_time);
 272             if ((__base.__state_ & __base.__n_readers_) == 0)
 273                 break;
 274             if (__status == cv_status::timeout)
 275             {
 276                 __base.__state_ &= ~__base.__write_entered_;
 277                 __base.__gate1_.notify_all();
 278                 return false;
 279             }
 280         }
 281     }
 282     return true;
 283 }
 284
 285 template <class _Clock, class _Duration>
 286 bool
 287 shared_timed_mutex::try_lock_shared_until(
 288                         const chrono::time_point<_Clock, _Duration>& __abs_time)
 289 {
 290     unique_lock<mutex> __lk(__base.__mut_);
 291     if ((__base.__state_ & __base.__write_entered_) || (__base.__state_ & __base.__n_readers_) == __base.__n_readers_)
 292     {
 293         while (true)
 294         {
 295             cv_status status = __base.__gate1_.wait_until(__lk, __abs_time);
 296             if ((__base.__state_ & __base.__write_entered_) == 0 &&
 297                                        (__base.__state_ & __base.__n_readers_) < __base.__n_readers_)
 298                 break;
 299             if (status == cv_status::timeout)
 300                 return false;
 301         }
 302     }
 303     unsigned __num_readers = (__base.__state_ & __base.__n_readers_) + 1;
 304     __base.__state_ &= ~__base.__n_readers_;
 305     __base.__state_ |= __num_readers;
 306     return true;
 307 }
 308
 309 template <class _Mutex>
 310 class shared_lock
 311 {
 312 public:
 313     typedef _Mutex mutex_type;
 314
 315 private:
 316     mutex_type* __m_;
 317     bool __owns_;
 318
 319 public:
 320     _LIBCPP_INLINE_VISIBILITY
 321     shared_lock() _NOEXCEPT
 322         : __m_(nullptr),
 323           __owns_(false)
 324         {}
 325
 326     _LIBCPP_INLINE_VISIBILITY
 327     explicit shared_lock(mutex_type& __m)
 328         : __m_(_VSTD::addressof(__m)),
 329           __owns_(true)
 330         {__m_->lock_shared();}
 331
 332     _LIBCPP_INLINE_VISIBILITY
 333     shared_lock(mutex_type& __m, defer_lock_t) _NOEXCEPT
 334         : __m_(_VSTD::addressof(__m)),
 335           __owns_(false)
 336         {}
 337
 338     _LIBCPP_INLINE_VISIBILITY
 339     shared_lock(mutex_type& __m, try_to_lock_t)
 340         : __m_(_VSTD::addressof(__m)),
 341           __owns_(__m.try_lock_shared())
 342         {}
 343
 344     _LIBCPP_INLINE_VISIBILITY
 345     shared_lock(mutex_type& __m, adopt_lock_t)
 346         : __m_(_VSTD::addressof(__m)),
 347           __owns_(true)
 348         {}
 349
 350     template <class _Clock, class _Duration>
 351         _LIBCPP_INLINE_VISIBILITY
 352         shared_lock(mutex_type& __m,
 353                     const chrono::time_point<_Clock, _Duration>& __abs_time)
 354             : __m_(_VSTD::addressof(__m)),
 355               __owns_(__m.try_lock_shared_until(__abs_time))
 356             {}
 357
 358     template <class _Rep, class _Period>
 359         _LIBCPP_INLINE_VISIBILITY
 360         shared_lock(mutex_type& __m,
 361                     const chrono::duration<_Rep, _Period>& __rel_time)
 362             : __m_(_VSTD::addressof(__m)),
 363               __owns_(__m.try_lock_shared_for(__rel_time))
 364             {}
 365
 366     _LIBCPP_INLINE_VISIBILITY
 367     ~shared_lock()
 368     {
 369         if (__owns_)
 370             __m_->unlock_shared();
 371     }
 372
 373     shared_lock(shared_lock const&) = delete;
 374     shared_lock& operator=(shared_lock const&) = delete;
 375
 376     _LIBCPP_INLINE_VISIBILITY
 377     shared_lock(shared_lock&& __u) _NOEXCEPT
 378         : __m_(__u.__m_),
 379           __owns_(__u.__owns_)
 380         {
 381             __u.__m_ = nullptr;
 382             __u.__owns_ = false;
 383         }
 384
 385     _LIBCPP_INLINE_VISIBILITY
 386     shared_lock& operator=(shared_lock&& __u) _NOEXCEPT
 387     {
 388         if (__owns_)
 389             __m_->unlock_shared();
 390         __m_ = nullptr;
 391         __owns_ = false;
 392         __m_ = __u.__m_;
 393         __owns_ = __u.__owns_;
 394         __u.__m_ = nullptr;
 395         __u.__owns_ = false;
 396         return *this;
 397     }
 398
 399     void lock();
 400     bool try_lock();
 401     template <class Rep, class Period>
 402         bool try_lock_for(const chrono::duration<Rep, Period>& rel_time);
 403     template <class Clock, class Duration>
 404         bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time);
 405     void unlock();
 406
 407     // Setters
 408     _LIBCPP_INLINE_VISIBILITY
 409     void swap(shared_lock& __u) _NOEXCEPT
 410     {
 411         _VSTD::swap(__m_, __u.__m_);
 412         _VSTD::swap(__owns_, __u.__owns_);
 413     }
 414
 415     _LIBCPP_INLINE_VISIBILITY
 416     mutex_type* release() _NOEXCEPT
 417     {
 418         mutex_type* __m = __m_;
 419         __m_ = nullptr;
 420         __owns_ = false;
 421         return __m;
 422     }
 423
 424     // Getters
 425     _LIBCPP_INLINE_VISIBILITY
 426     bool owns_lock() const _NOEXCEPT {return __owns_;}
 427
 428     _LIBCPP_INLINE_VISIBILITY
 429     explicit operator bool () const _NOEXCEPT {return __owns_;}
 430
 431     _LIBCPP_INLINE_VISIBILITY
 432     mutex_type* mutex() const _NOEXCEPT {return __m_;}
 433 };
 434
 435 template <class _Mutex>
 436 void
 437 shared_lock<_Mutex>::lock()
 438 {
 439     if (__m_ == nullptr)
 440         __throw_system_error(EPERM, "shared_lock::lock: references null mutex");
 441     if (__owns_)
 442         __throw_system_error(EDEADLK, "shared_lock::lock: already locked");
 443     __m_->lock_shared();
 444     __owns_ = true;
 445 }
 446
 447 template <class _Mutex>
 448 bool
 449 shared_lock<_Mutex>::try_lock()
 450 {
 451     if (__m_ == nullptr)
 452         __throw_system_error(EPERM, "shared_lock::try_lock: references null mutex");
 453     if (__owns_)
 454         __throw_system_error(EDEADLK, "shared_lock::try_lock: already locked");
 455     __owns_ = __m_->try_lock_shared();
 456     return __owns_;
 457 }
 458
 459 template <class _Mutex>
 460 template <class _Rep, class _Period>
 461 bool
 462 shared_lock<_Mutex>::try_lock_for(const chrono::duration<_Rep, _Period>& __d)
 463 {
 464     if (__m_ == nullptr)
 465         __throw_system_error(EPERM, "shared_lock::try_lock_for: references null mutex");
 466     if (__owns_)
 467         __throw_system_error(EDEADLK, "shared_lock::try_lock_for: already locked");
 468     __owns_ = __m_->try_lock_shared_for(__d);
 469     return __owns_;
 470 }
 471
 472 template <class _Mutex>
 473 template <class _Clock, class _Duration>
 474 bool
 475 shared_lock<_Mutex>::try_lock_until(const chrono::time_point<_Clock, _Duration>& __t)
 476 {
 477     if (__m_ == nullptr)
 478         __throw_system_error(EPERM, "shared_lock::try_lock_until: references null mutex");
 479     if (__owns_)
 480         __throw_system_error(EDEADLK, "shared_lock::try_lock_until: already locked");
 481     __owns_ = __m_->try_lock_shared_until(__t);
 482     return __owns_;
 483 }
 484
 485 template <class _Mutex>
 486 void
 487 shared_lock<_Mutex>::unlock()
 488 {
 489     if (!__owns_)
 490         __throw_system_error(EPERM, "shared_lock::unlock: not locked");
 491     __m_->unlock_shared();
 492     __owns_ = false;
 493 }
 494
 495 template <class _Mutex>
 496 inline _LIBCPP_INLINE_VISIBILITY
 497 void
 498 swap(shared_lock<_Mutex>& __x, shared_lock<_Mutex>& __y) _NOEXCEPT
 499     {__x.swap(__y);}
 500
 501 _LIBCPP_END_NAMESPACE_STD
 502
 503 #endif // !_LIBCPP_HAS_NO_THREADS
 504
 505 #endif // _LIBCPP_STD_VER > 11
 506
 507 _LIBCPP_POP_MACROS
 508
 509 #endif // _LIBCPP_SHARED_MUTEX