1// std::mutex implementation -*- 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 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
43namespace 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    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    mutex() noexcept = default;
92    ~mutex() = default;
93
94    mutex(const mutex&) = delete;
95    mutex& operator=(const mutex&) = delete;
96
97    void
98    lock()
99    {
100      int __e = __gthread_mutex_lock(&_M_mutex);
101
102      // EINVAL, EAGAIN, EBUSY, EINVAL, EDEADLK(may)
103      if (__e)
104	__throw_system_error(__e);
105    }
106
107    bool
108    try_lock() noexcept
109    {
110      // XXX EINVAL, EAGAIN, EBUSY
111      return !__gthread_mutex_trylock(&_M_mutex);
112    }
113
114    void
115    unlock()
116    {
117      // XXX EINVAL, EAGAIN, EPERM
118      __gthread_mutex_unlock(&_M_mutex);
119    }
120
121    native_handle_type
122    native_handle() noexcept
123    { return &_M_mutex; }
124  };
125
126#endif // _GLIBCXX_HAS_GTHREADS
127
128  /// Do not acquire ownership of the mutex.
129  struct defer_lock_t { explicit defer_lock_t() = default; };
130
131  /// Try to acquire ownership of the mutex without blocking.
132  struct try_to_lock_t { explicit try_to_lock_t() = default; };
133
134  /// Assume the calling thread has already obtained mutex ownership
135  /// and manage it.
136  struct adopt_lock_t { explicit adopt_lock_t() = default; };
137
138  /// Tag used to prevent a scoped lock from acquiring ownership of a mutex.
139  _GLIBCXX17_INLINE constexpr defer_lock_t	defer_lock { };
140
141  /// Tag used to prevent a scoped lock from blocking if a mutex is locked.
142  _GLIBCXX17_INLINE constexpr try_to_lock_t	try_to_lock { };
143
144  /// Tag used to make a scoped lock take ownership of a locked mutex.
145  _GLIBCXX17_INLINE constexpr adopt_lock_t	adopt_lock { };
146
147  /** @brief A simple scoped lock type.
148   *
149   * A lock_guard controls mutex ownership within a scope, releasing
150   * ownership in the destructor.
151   */
152  template<typename _Mutex>
153    class lock_guard
154    {
155    public:
156      typedef _Mutex mutex_type;
157
158      explicit lock_guard(mutex_type& __m) : _M_device(__m)
159      { _M_device.lock(); }
160
161      lock_guard(mutex_type& __m, adopt_lock_t) noexcept : _M_device(__m)
162      { } // calling thread owns mutex
163
164      ~lock_guard()
165      { _M_device.unlock(); }
166
167      lock_guard(const lock_guard&) = delete;
168      lock_guard& operator=(const lock_guard&) = delete;
169
170    private:
171      mutex_type&  _M_device;
172    };
173
174  /// @} group mutexes
175_GLIBCXX_END_NAMESPACE_VERSION
176} // namespace
177#endif // C++11
178#endif // _GLIBCXX_MUTEX_H
179