libstdc++
shared_ptr_atomic.h
Go to the documentation of this file.
1 // shared_ptr atomic access -*- C++ -*-
2 
3 // Copyright (C) 2014-2017 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/shared_ptr_atomic.h
26  * This is an internal header file, included by other library headers.
27  * Do not attempt to use it directly. @headername{memory}
28  */
29 
30 #ifndef _SHARED_PTR_ATOMIC_H
31 #define _SHARED_PTR_ATOMIC_H 1
32 
33 #include <bits/atomic_base.h>
34 
35 namespace std _GLIBCXX_VISIBILITY(default)
36 {
37 _GLIBCXX_BEGIN_NAMESPACE_VERSION
38 
39  /**
40  * @addtogroup pointer_abstractions
41  * @{
42  */
43 
44  struct _Sp_locker
45  {
46  _Sp_locker(const _Sp_locker&) = delete;
47  _Sp_locker& operator=(const _Sp_locker&) = delete;
48 
49 #ifdef __GTHREADS
50  explicit
51  _Sp_locker(const void*) noexcept;
52  _Sp_locker(const void*, const void*) noexcept;
53  ~_Sp_locker();
54 
55  private:
56  unsigned char _M_key1;
57  unsigned char _M_key2;
58 #else
59  explicit _Sp_locker(const void*, const void* = nullptr) { }
60 #endif
61  };
62 
63  /**
64  * @brief Report whether shared_ptr atomic operations are lock-free.
65  * @param __p A non-null pointer to a shared_ptr object.
66  * @return True if atomic access to @c *__p is lock-free, false otherwise.
67  * @{
68  */
69  template<typename _Tp, _Lock_policy _Lp>
70  inline bool
71  atomic_is_lock_free(const __shared_ptr<_Tp, _Lp>* __p)
72  {
73 #ifdef __GTHREADS
74  return __gthread_active_p() == 0;
75 #else
76  return true;
77 #endif
78  }
79 
80  template<typename _Tp>
81  inline bool
82  atomic_is_lock_free(const shared_ptr<_Tp>* __p)
83  { return std::atomic_is_lock_free<_Tp, __default_lock_policy>(__p); }
84 
85  // @}
86 
87  /**
88  * @brief Atomic load for shared_ptr objects.
89  * @param __p A non-null pointer to a shared_ptr object.
90  * @return @c *__p
91  *
92  * The memory order shall not be @c memory_order_release or
93  * @c memory_order_acq_rel.
94  * @{
95  */
96  template<typename _Tp>
97  inline shared_ptr<_Tp>
98  atomic_load_explicit(const shared_ptr<_Tp>* __p, memory_order)
99  {
100  _Sp_locker __lock{__p};
101  return *__p;
102  }
103 
104  template<typename _Tp>
105  inline shared_ptr<_Tp>
106  atomic_load(const shared_ptr<_Tp>* __p)
107  { return std::atomic_load_explicit(__p, memory_order_seq_cst); }
108 
109  template<typename _Tp, _Lock_policy _Lp>
110  inline __shared_ptr<_Tp, _Lp>
111  atomic_load_explicit(const __shared_ptr<_Tp, _Lp>* __p, memory_order)
112  {
113  _Sp_locker __lock{__p};
114  return *__p;
115  }
116 
117  template<typename _Tp, _Lock_policy _Lp>
118  inline __shared_ptr<_Tp, _Lp>
119  atomic_load(const __shared_ptr<_Tp, _Lp>* __p)
120  { return std::atomic_load_explicit(__p, memory_order_seq_cst); }
121  // @}
122 
123  /**
124  * @brief Atomic store for shared_ptr objects.
125  * @param __p A non-null pointer to a shared_ptr object.
126  * @param __r The value to store.
127  *
128  * The memory order shall not be @c memory_order_acquire or
129  * @c memory_order_acq_rel.
130  * @{
131  */
132  template<typename _Tp>
133  inline void
134  atomic_store_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r,
135  memory_order)
136  {
137  _Sp_locker __lock{__p};
138  __p->swap(__r); // use swap so that **__p not destroyed while lock held
139  }
140 
141  template<typename _Tp>
142  inline void
143  atomic_store(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r)
144  { std::atomic_store_explicit(__p, std::move(__r), memory_order_seq_cst); }
145 
146  template<typename _Tp, _Lock_policy _Lp>
147  inline void
148  atomic_store_explicit(__shared_ptr<_Tp, _Lp>* __p,
149  __shared_ptr<_Tp, _Lp> __r,
150  memory_order)
151  {
152  _Sp_locker __lock{__p};
153  __p->swap(__r); // use swap so that **__p not destroyed while lock held
154  }
155 
156  template<typename _Tp, _Lock_policy _Lp>
157  inline void
158  atomic_store(__shared_ptr<_Tp, _Lp>* __p, __shared_ptr<_Tp, _Lp> __r)
159  { std::atomic_store_explicit(__p, std::move(__r), memory_order_seq_cst); }
160  // @}
161 
162  /**
163  * @brief Atomic exchange for shared_ptr objects.
164  * @param __p A non-null pointer to a shared_ptr object.
165  * @param __r New value to store in @c *__p.
166  * @return The original value of @c *__p
167  * @{
168  */
169  template<typename _Tp>
170  inline shared_ptr<_Tp>
171  atomic_exchange_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r,
172  memory_order)
173  {
174  _Sp_locker __lock{__p};
175  __p->swap(__r);
176  return __r;
177  }
178 
179  template<typename _Tp>
180  inline shared_ptr<_Tp>
181  atomic_exchange(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r)
182  {
183  return std::atomic_exchange_explicit(__p, std::move(__r),
184  memory_order_seq_cst);
185  }
186 
187  template<typename _Tp, _Lock_policy _Lp>
188  inline __shared_ptr<_Tp, _Lp>
189  atomic_exchange_explicit(__shared_ptr<_Tp, _Lp>* __p,
190  __shared_ptr<_Tp, _Lp> __r,
191  memory_order)
192  {
193  _Sp_locker __lock{__p};
194  __p->swap(__r);
195  return __r;
196  }
197 
198  template<typename _Tp, _Lock_policy _Lp>
199  inline __shared_ptr<_Tp, _Lp>
200  atomic_exchange(__shared_ptr<_Tp, _Lp>* __p, __shared_ptr<_Tp, _Lp> __r)
201  {
202  return std::atomic_exchange_explicit(__p, std::move(__r),
203  memory_order_seq_cst);
204  }
205  // @}
206 
207  /**
208  * @brief Atomic compare-and-swap for shared_ptr objects.
209  * @param __p A non-null pointer to a shared_ptr object.
210  * @param __v A non-null pointer to a shared_ptr object.
211  * @param __w A non-null pointer to a shared_ptr object.
212  * @return True if @c *__p was equivalent to @c *__v, false otherwise.
213  *
214  * The memory order for failure shall not be @c memory_order_release or
215  * @c memory_order_acq_rel, or stronger than the memory order for success.
216  * @{
217  */
218  template<typename _Tp>
219  bool
220  atomic_compare_exchange_strong_explicit(shared_ptr<_Tp>* __p,
221  shared_ptr<_Tp>* __v,
222  shared_ptr<_Tp> __w,
223  memory_order,
224  memory_order)
225  {
226  shared_ptr<_Tp> __x; // goes out of scope after __lock
227  _Sp_locker __lock{__p, __v};
229  if (*__p == *__v && !__less(*__p, *__v) && !__less(*__v, *__p))
230  {
231  __x = std::move(*__p);
232  *__p = std::move(__w);
233  return true;
234  }
235  __x = std::move(*__v);
236  *__v = *__p;
237  return false;
238  }
239 
240  template<typename _Tp>
241  inline bool
242  atomic_compare_exchange_strong(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v,
243  shared_ptr<_Tp> __w)
244  {
246  std::move(__w), memory_order_seq_cst, memory_order_seq_cst);
247  }
248 
249  template<typename _Tp>
250  inline bool
251  atomic_compare_exchange_weak_explicit(shared_ptr<_Tp>* __p,
252  shared_ptr<_Tp>* __v,
253  shared_ptr<_Tp> __w,
254  memory_order __success,
255  memory_order __failure)
256  {
258  std::move(__w), __success, __failure);
259  }
260 
261  template<typename _Tp>
262  inline bool
263  atomic_compare_exchange_weak(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v,
264  shared_ptr<_Tp> __w)
265  {
267  std::move(__w), memory_order_seq_cst, memory_order_seq_cst);
268  }
269 
270  template<typename _Tp, _Lock_policy _Lp>
271  bool
272  atomic_compare_exchange_strong_explicit(__shared_ptr<_Tp, _Lp>* __p,
273  __shared_ptr<_Tp, _Lp>* __v,
274  __shared_ptr<_Tp, _Lp> __w,
275  memory_order,
276  memory_order)
277  {
278  __shared_ptr<_Tp, _Lp> __x; // goes out of scope after __lock
279  _Sp_locker __lock{__p, __v};
281  if (*__p == *__v && !__less(*__p, *__v) && !__less(*__v, *__p))
282  {
283  __x = std::move(*__p);
284  *__p = std::move(__w);
285  return true;
286  }
287  __x = std::move(*__v);
288  *__v = *__p;
289  return false;
290  }
291 
292  template<typename _Tp, _Lock_policy _Lp>
293  inline bool
294  atomic_compare_exchange_strong(__shared_ptr<_Tp, _Lp>* __p,
295  __shared_ptr<_Tp, _Lp>* __v,
296  __shared_ptr<_Tp, _Lp> __w)
297  {
299  std::move(__w), memory_order_seq_cst, memory_order_seq_cst);
300  }
301 
302  template<typename _Tp, _Lock_policy _Lp>
303  inline bool
304  atomic_compare_exchange_weak_explicit(__shared_ptr<_Tp, _Lp>* __p,
305  __shared_ptr<_Tp, _Lp>* __v,
306  __shared_ptr<_Tp, _Lp> __w,
307  memory_order __success,
308  memory_order __failure)
309  {
311  std::move(__w), __success, __failure);
312  }
313 
314  template<typename _Tp, _Lock_policy _Lp>
315  inline bool
316  atomic_compare_exchange_weak(__shared_ptr<_Tp, _Lp>* __p,
317  __shared_ptr<_Tp, _Lp>* __v,
318  __shared_ptr<_Tp, _Lp> __w)
319  {
321  std::move(__w), memory_order_seq_cst, memory_order_seq_cst);
322  }
323  // @}
324 
325  // @} group pointer_abstractions
326 
327 _GLIBCXX_END_NAMESPACE_VERSION
328 } // namespace
329 
330 #endif // _SHARED_PTR_ATOMIC_H
bool atomic_compare_exchange_strong_explicit(__shared_ptr< _Tp, _Lp > *__p, __shared_ptr< _Tp, _Lp > *__v, __shared_ptr< _Tp, _Lp > __w, memory_order, memory_order)
Atomic compare-and-swap for shared_ptr objects.
bool atomic_compare_exchange_weak_explicit(__shared_ptr< _Tp, _Lp > *__p, __shared_ptr< _Tp, _Lp > *__v, __shared_ptr< _Tp, _Lp > __w, memory_order __success, memory_order __failure)
Atomic compare-and-swap for shared_ptr objects.
__shared_ptr< _Tp, _Lp > atomic_load_explicit(const __shared_ptr< _Tp, _Lp > *__p, memory_order)
Atomic load for shared_ptr objects.
__shared_ptr< _Tp, _Lp > atomic_exchange_explicit(__shared_ptr< _Tp, _Lp > *__p, __shared_ptr< _Tp, _Lp > __r, memory_order)
Atomic exchange for shared_ptr objects.
memory_order
Enumeration for memory_order.
Definition: atomic_base.h:55
ISO C++ entities toplevel namespace is std.
void atomic_store_explicit(__shared_ptr< _Tp, _Lp > *__p, __shared_ptr< _Tp, _Lp > __r, memory_order)
Atomic store for shared_ptr objects.
A smart pointer with reference-counted copy semantics.
Primary template owner_less.