libstdc++-v3/include/bits/std_mutex.h

   1 // std::mutex implementation -*- C++ -*-
   2
   3 // Copyright (C) 2003-2018 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 bits/std_mutex.h
  26  *  This is an internal header file, included by other library headers.
  27  *  Do not attempt to use it directly. @headername{mutex}
  28  */
  29
  30 #ifndef _GLIBCXX_MUTEX_H
  31 #define _GLIBCXX_MUTEX_H 1
  32
  33 #pragma GCC system_header
  34
  35 #if __cplusplus < 201103L
  36 # include <bits/c++0x_warning.h>
  37 #else
  38
  39 #include <system_error>
  40 #include <bits/functexcept.h>
  41 #include <bits/gthr.h>
  42 #include <bits/move.h> // for std::swap
  43
  44 #ifdef _GLIBCXX_USE_C99_STDINT_TR1
  45
  46 namespace std _GLIBCXX_VISIBILITY(default)
  47 {
  48 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  49
  50   /**
  51    * @defgroup mutexes Mutexes
  52    * @ingroup concurrency
  53    *
  54    * Classes for mutex support.
  55    * @{
  56    */
  57
  58 #ifdef _GLIBCXX_HAS_GTHREADS
  59   // Common base class for std::mutex and std::timed_mutex
  60   class __mutex_base
  61   {
  62   protected:
  63     typedef __gthread_mutex_t                   __native_type;
  64
  65 #ifdef __GTHREAD_MUTEX_INIT
  66     __native_type  _M_mutex = __GTHREAD_MUTEX_INIT;
  67
  68     constexpr __mutex_base() noexcept = default;
  69 #else
  70     __native_type  _M_mutex;
  71
  72     __mutex_base() noexcept
  73     {
  74       // XXX EAGAIN, ENOMEM, EPERM, EBUSY(may), EINVAL(may)
  75       __GTHREAD_MUTEX_INIT_FUNCTION(&_M_mutex);
  76     }
  77
  78     ~__mutex_base() noexcept { __gthread_mutex_destroy(&_M_mutex); }
  79 #endif
  80
  81     __mutex_base(const __mutex_base&) = delete;
  82     __mutex_base& operator=(const __mutex_base&) = delete;
  83   };
  84
  85   /// The standard mutex type.
  86   class mutex : private __mutex_base
  87   {
  88   public:
  89     typedef __native_type*                      native_handle_type;
  90
  91 #ifdef __GTHREAD_MUTEX_INIT
  92     constexpr
  93 #endif
  94     mutex() noexcept = default;
  95     ~mutex() = default;
  96
  97     mutex(const mutex&) = delete;
  98     mutex& operator=(const mutex&) = delete;
  99
 100     void
 101     lock()
 102     {
 103       int __e = __gthread_mutex_lock(&_M_mutex);
 104
 105       // EINVAL, EAGAIN, EBUSY, EINVAL, EDEADLK(may)
 106       if (__e)
 107         __throw_system_error(__e);
 108     }
 109
 110     bool
 111     try_lock() noexcept
 112     {
 113       // XXX EINVAL, EAGAIN, EBUSY
 114       return !__gthread_mutex_trylock(&_M_mutex);
 115     }
 116
 117     void
 118     unlock()
 119     {
 120       // XXX EINVAL, EAGAIN, EPERM
 121       __gthread_mutex_unlock(&_M_mutex);
 122     }
 123
 124     native_handle_type
 125     native_handle() noexcept
 126     { return &_M_mutex; }
 127   };
 128
 129 #endif // _GLIBCXX_HAS_GTHREADS
 130
 131   /// Do not acquire ownership of the mutex.
 132   struct defer_lock_t { explicit defer_lock_t() = default; };
 133
 134   /// Try to acquire ownership of the mutex without blocking.
 135   struct try_to_lock_t { explicit try_to_lock_t() = default; };
 136
 137   /// Assume the calling thread has already obtained mutex ownership
 138   /// and manage it.
 139   struct adopt_lock_t { explicit adopt_lock_t() = default; };
 140
 141   /// Tag used to prevent a scoped lock from acquiring ownership of a mutex.
 142   _GLIBCXX17_INLINE constexpr defer_lock_t      defer_lock { };
 143
 144   /// Tag used to prevent a scoped lock from blocking if a mutex is locked.
 145   _GLIBCXX17_INLINE constexpr try_to_lock_t     try_to_lock { };
 146
 147   /// Tag used to make a scoped lock take ownership of a locked mutex.
 148   _GLIBCXX17_INLINE constexpr adopt_lock_t      adopt_lock { };
 149
 150   /** @brief A simple scoped lock type.
 151    *
 152    * A lock_guard controls mutex ownership within a scope, releasing
 153    * ownership in the destructor.
 154    */
 155   template<typename _Mutex>
 156     class lock_guard
 157     {
 158     public:
 159       typedef _Mutex mutex_type;
 160
 161       explicit lock_guard(mutex_type& __m) : _M_device(__m)
 162       { _M_device.lock(); }
 163
 164       lock_guard(mutex_type& __m, adopt_lock_t) noexcept : _M_device(__m)
 165       { } // calling thread owns mutex
 166
 167       ~lock_guard()
 168       { _M_device.unlock(); }
 169
 170       lock_guard(const lock_guard&) = delete;
 171       lock_guard& operator=(const lock_guard&) = delete;
 172
 173     private:
 174       mutex_type&  _M_device;
 175     };
 176
 177   /** @brief A movable scoped lock type.
 178    *
 179    * A unique_lock controls mutex ownership within a scope. Ownership of the
 180    * mutex can be delayed until after construction and can be transferred
 181    * to another unique_lock by move construction or move assignment. If a
 182    * mutex lock is owned when the destructor runs ownership will be released.
 183    */
 184   template<typename _Mutex>
 185     class unique_lock
 186     {
 187     public:
 188       typedef _Mutex mutex_type;
 189
 190       unique_lock() noexcept
 191       : _M_device(0), _M_owns(false)
 192       { }
 193
 194       explicit unique_lock(mutex_type& __m)
 195       : _M_device(std::__addressof(__m)), _M_owns(false)
 196       {
 197         lock();
 198         _M_owns = true;
 199       }
 200
 201       unique_lock(mutex_type& __m, defer_lock_t) noexcept
 202       : _M_device(std::__addressof(__m)), _M_owns(false)
 203       { }
 204
 205       unique_lock(mutex_type& __m, try_to_lock_t)
 206       : _M_device(std::__addressof(__m)), _M_owns(_M_device->try_lock())
 207       { }
 208
 209       unique_lock(mutex_type& __m, adopt_lock_t) noexcept
 210       : _M_device(std::__addressof(__m)), _M_owns(true)
 211       {
 212         // XXX calling thread owns mutex
 213       }
 214
 215       template<typename _Clock, typename _Duration>
 216         unique_lock(mutex_type& __m,
 217                     const chrono::time_point<_Clock, _Duration>& __atime)
 218         : _M_device(std::__addressof(__m)),
 219           _M_owns(_M_device->try_lock_until(__atime))
 220         { }
 221
 222       template<typename _Rep, typename _Period>
 223         unique_lock(mutex_type& __m,
 224                     const chrono::duration<_Rep, _Period>& __rtime)
 225         : _M_device(std::__addressof(__m)),
 226           _M_owns(_M_device->try_lock_for(__rtime))
 227         { }
 228
 229       ~unique_lock()
 230       {
 231         if (_M_owns)
 232           unlock();
 233       }
 234
 235       unique_lock(const unique_lock&) = delete;
 236       unique_lock& operator=(const unique_lock&) = delete;
 237
 238       unique_lock(unique_lock&& __u) noexcept
 239       : _M_device(__u._M_device), _M_owns(__u._M_owns)
 240       {
 241         __u._M_device = 0;
 242         __u._M_owns = false;
 243       }
 244
 245       unique_lock& operator=(unique_lock&& __u) noexcept
 246       {
 247         if(_M_owns)
 248           unlock();
 249
 250         unique_lock(std::move(__u)).swap(*this);
 251
 252         __u._M_device = 0;
 253         __u._M_owns = false;
 254
 255         return *this;
 256       }
 257
 258       void
 259       lock()
 260       {
 261         if (!_M_device)
 262           __throw_system_error(int(errc::operation_not_permitted));
 263         else if (_M_owns)
 264           __throw_system_error(int(errc::resource_deadlock_would_occur));
 265         else
 266           {
 267             _M_device->lock();
 268             _M_owns = true;
 269           }
 270       }
 271
 272       bool
 273       try_lock()
 274       {
 275         if (!_M_device)
 276           __throw_system_error(int(errc::operation_not_permitted));
 277         else if (_M_owns)
 278           __throw_system_error(int(errc::resource_deadlock_would_occur));
 279         else
 280           {
 281             _M_owns = _M_device->try_lock();
 282             return _M_owns;
 283           }
 284       }
 285
 286       template<typename _Clock, typename _Duration>
 287         bool
 288         try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime)
 289         {
 290           if (!_M_device)
 291             __throw_system_error(int(errc::operation_not_permitted));
 292           else if (_M_owns)
 293             __throw_system_error(int(errc::resource_deadlock_would_occur));
 294           else
 295             {
 296               _M_owns = _M_device->try_lock_until(__atime);
 297               return _M_owns;
 298             }
 299         }
 300
 301       template<typename _Rep, typename _Period>
 302         bool
 303         try_lock_for(const chrono::duration<_Rep, _Period>& __rtime)
 304         {
 305           if (!_M_device)
 306             __throw_system_error(int(errc::operation_not_permitted));
 307           else if (_M_owns)
 308             __throw_system_error(int(errc::resource_deadlock_would_occur));
 309           else
 310             {
 311               _M_owns = _M_device->try_lock_for(__rtime);
 312               return _M_owns;
 313             }
 314          }
 315
 316       void
 317       unlock()
 318       {
 319         if (!_M_owns)
 320           __throw_system_error(int(errc::operation_not_permitted));
 321         else if (_M_device)
 322           {
 323             _M_device->unlock();
 324             _M_owns = false;
 325           }
 326       }
 327
 328       void
 329       swap(unique_lock& __u) noexcept
 330       {
 331         std::swap(_M_device, __u._M_device);
 332         std::swap(_M_owns, __u._M_owns);
 333       }
 334
 335       mutex_type*
 336       release() noexcept
 337       {
 338         mutex_type* __ret = _M_device;
 339         _M_device = 0;
 340         _M_owns = false;
 341         return __ret;
 342       }
 343
 344       bool
 345       owns_lock() const noexcept
 346       { return _M_owns; }
 347
 348       explicit operator bool() const noexcept
 349       { return owns_lock(); }
 350
 351       mutex_type*
 352       mutex() const noexcept
 353       { return _M_device; }
 354
 355     private:
 356       mutex_type*       _M_device;
 357       bool              _M_owns; // XXX use atomic_bool
 358     };
 359
 360   /// Swap overload for unique_lock objects.
 361   template<typename _Mutex>
 362     inline void
 363     swap(unique_lock<_Mutex>& __x, unique_lock<_Mutex>& __y) noexcept
 364     { __x.swap(__y); }
 365
 366   // @} group mutexes
 367 _GLIBCXX_END_NAMESPACE_VERSION
 368 } // namespace
 369 #endif // _GLIBCXX_USE_C99_STDINT_TR1
 370
 371 #endif // C++11
 372
 373 #endif // _GLIBCXX_MUTEX_H