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 
_GLIBCXX_VISIBILITY(default)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
374