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       1             : // std::mutex implementation -*- C++ -*-
       2             : 
       3             : // Copyright (C) 2003-2021 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             : 
      43             : namespace std _GLIBCXX_VISIBILITY(default)
      44             : {
      45             : _GLIBCXX_BEGIN_NAMESPACE_VERSION
      46             : 
      47             :   /**
      48             :    * @defgroup mutexes Mutexes
      49             :    * @ingroup concurrency
      50             :    *
      51             :    * Classes for mutex support.
      52             :    * @{
      53             :    */
      54             : 
      55             : #ifdef _GLIBCXX_HAS_GTHREADS
      56             :   // Common base class for std::mutex and std::timed_mutex
      57             :   class __mutex_base
      58             :   {
      59             :   protected:
      60             :     typedef __gthread_mutex_t                   __native_type;
      61             : 
      62             : #ifdef __GTHREAD_MUTEX_INIT
      63             :     __native_type  _M_mutex = __GTHREAD_MUTEX_INIT;
      64             : 
      65       56849 :     constexpr __mutex_base() noexcept = default;
      66             : #else
      67             :     __native_type  _M_mutex;
      68             : 
      69             :     __mutex_base() noexcept
      70             :     {
      71             :       // XXX EAGAIN, ENOMEM, EPERM, EBUSY(may), EINVAL(may)
      72             :       __GTHREAD_MUTEX_INIT_FUNCTION(&_M_mutex);
      73             :     }
      74             : 
      75             :     ~__mutex_base() noexcept { __gthread_mutex_destroy(&_M_mutex); }
      76             : #endif
      77             : 
      78             :     __mutex_base(const __mutex_base&) = delete;
      79             :     __mutex_base& operator=(const __mutex_base&) = delete;
      80             :   };
      81             : 
      82             :   /// The standard mutex type.
      83             :   class mutex : private __mutex_base
      84             :   {
      85             :   public:
      86             :     typedef __native_type*                      native_handle_type;
      87             : 
      88             : #ifdef __GTHREAD_MUTEX_INIT
      89             :     constexpr
      90             : #endif
      91       56849 :     mutex() noexcept = default;
      92             :     ~mutex() = default;
      93             : 
      94             :     mutex(const mutex&) = delete;
      95             :     mutex& operator=(const mutex&) = delete;
      96             : 
      97             :     void
      98      605122 :     lock()
      99             :     {
     100      605122 :       int __e = __gthread_mutex_lock(&_M_mutex);
     101             : 
     102             :       // EINVAL, EAGAIN, EBUSY, EINVAL, EDEADLK(may)
     103      605197 :       if (__e)
     104           0 :         __throw_system_error(__e);
     105      605197 :     }
     106             : 
     107             :     bool
     108         340 :     try_lock() noexcept
     109             :     {
     110             :       // XXX EINVAL, EAGAIN, EBUSY
     111         340 :       return !__gthread_mutex_trylock(&_M_mutex);
     112             :     }
     113             : 
     114             :     void
     115      617022 :     unlock()
     116             :     {
     117             :       // XXX EINVAL, EAGAIN, EPERM
     118      617022 :       __gthread_mutex_unlock(&_M_mutex);
     119      617135 :     }
     120             : 
     121             :     native_handle_type
     122        6912 :     native_handle() noexcept
     123        6912 :     { return &_M_mutex; }
     124             :   };
     125             : 
     126             :   // Implementation details for std::condition_variable
     127             :   class __condvar
     128             :   {
     129             :     using timespec = __gthread_time_t;
     130             : 
     131             :   public:
     132             :     __condvar() noexcept
     133             :     {
     134             : #ifndef __GTHREAD_COND_INIT
     135             :       __GTHREAD_COND_INIT_FUNCTION(&_M_cond);
     136             : #endif
     137             :     }
     138             : 
     139             :     ~__condvar()
     140             :     {
     141             :       int __e __attribute__((__unused__)) = __gthread_cond_destroy(&_M_cond);
     142             :       __glibcxx_assert(__e != EBUSY); // threads are still blocked
     143             :     }
     144             : 
     145             :     __condvar(const __condvar&) = delete;
     146             :     __condvar& operator=(const __condvar&) = delete;
     147             : 
     148             :     __gthread_cond_t* native_handle() noexcept { return &_M_cond; }
     149             : 
     150             :     // Expects: Calling thread has locked __m.
     151             :     void
     152             :     wait(mutex& __m) noexcept
     153             :     {
     154             :       int __e __attribute__((__unused__))
     155             :         = __gthread_cond_wait(&_M_cond, __m.native_handle());
     156             :       __glibcxx_assert(__e == 0);
     157             :     }
     158             : 
     159             :     void
     160           0 :     wait_until(mutex& __m, timespec& __abs_time) noexcept
     161             :     {
     162           0 :       __gthread_cond_timedwait(&_M_cond, __m.native_handle(), &__abs_time);
     163           0 :     }
     164             : 
     165             : #ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
     166             :     void
     167        6912 :     wait_until(mutex& __m, clockid_t __clock, timespec& __abs_time) noexcept
     168             :     {
     169        6912 :       pthread_cond_clockwait(&_M_cond, __m.native_handle(), __clock,
     170             :                              &__abs_time);
     171        6916 :     }
     172             : #endif
     173             : 
     174             :     void
     175             :     notify_one() noexcept
     176             :     {
     177             :       int __e __attribute__((__unused__)) = __gthread_cond_signal(&_M_cond);
     178             :       __glibcxx_assert(__e == 0);
     179             :     }
     180             : 
     181             :     void
     182             :     notify_all() noexcept
     183             :     {
     184             :       int __e __attribute__((__unused__)) = __gthread_cond_broadcast(&_M_cond);
     185             :       __glibcxx_assert(__e == 0);
     186             :     }
     187             : 
     188             :   protected:
     189             : #ifdef __GTHREAD_COND_INIT
     190             :     __gthread_cond_t _M_cond = __GTHREAD_COND_INIT;
     191             : #else
     192             :     __gthread_cond_t _M_cond;
     193             : #endif
     194             :   };
     195             : 
     196             : #endif // _GLIBCXX_HAS_GTHREADS
     197             : 
     198             :   /// Do not acquire ownership of the mutex.
     199             :   struct defer_lock_t { explicit defer_lock_t() = default; };
     200             : 
     201             :   /// Try to acquire ownership of the mutex without blocking.
     202             :   struct try_to_lock_t { explicit try_to_lock_t() = default; };
     203             : 
     204             :   /// Assume the calling thread has already obtained mutex ownership
     205             :   /// and manage it.
     206             :   struct adopt_lock_t { explicit adopt_lock_t() = default; };
     207             : 
     208             :   /// Tag used to prevent a scoped lock from acquiring ownership of a mutex.
     209             :   _GLIBCXX17_INLINE constexpr defer_lock_t      defer_lock { };
     210             : 
     211             :   /// Tag used to prevent a scoped lock from blocking if a mutex is locked.
     212             :   _GLIBCXX17_INLINE constexpr try_to_lock_t     try_to_lock { };
     213             : 
     214             :   /// Tag used to make a scoped lock take ownership of a locked mutex.
     215             :   _GLIBCXX17_INLINE constexpr adopt_lock_t      adopt_lock { };
     216             : 
     217             :   /** @brief A simple scoped lock type.
     218             :    *
     219             :    * A lock_guard controls mutex ownership within a scope, releasing
     220             :    * ownership in the destructor.
     221             :    */
     222             :   template<typename _Mutex>
     223             :     class lock_guard
     224             :     {
     225             :     public:
     226             :       typedef _Mutex mutex_type;
     227             : 
     228      648777 :       explicit lock_guard(mutex_type& __m) : _M_device(__m)
     229      648777 :       { _M_device.lock(); }
     230             : 
     231         156 :       lock_guard(mutex_type& __m, adopt_lock_t) noexcept : _M_device(__m)
     232         156 :       { } // calling thread owns mutex
     233             : 
     234      648942 :       ~lock_guard()
     235      648942 :       { _M_device.unlock(); }
     236             : 
     237             :       lock_guard(const lock_guard&) = delete;
     238             :       lock_guard& operator=(const lock_guard&) = delete;
     239             : 
     240             :     private:
     241             :       mutex_type&  _M_device;
     242             :     };
     243             : 
     244             :   /// @} group mutexes
     245             : _GLIBCXX_END_NAMESPACE_VERSION
     246             : } // namespace
     247             : #endif // C++11
     248             : #endif // _GLIBCXX_MUTEX_H