source: Daodan/MSYS2/mingw32/include/c++/11.2.0/bits/atomic_timed_wait.h

Last change on this file was 1166, checked in by rossy, 3 years ago

Daodan: Replace MinGW build env with an up-to-date MSYS2 env
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[1166]1// -*- C++ -*- header.
2
3// Copyright (C) 2020-2021 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/atomic_timed_wait.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly. @headername{atomic}
28 */
29
30#ifndef _GLIBCXX_ATOMIC_TIMED_WAIT_H
31#define _GLIBCXX_ATOMIC_TIMED_WAIT_H 1
32
33#pragma GCC system_header
34
35#include <bits/atomic_wait.h>
36
37#if __cpp_lib_atomic_wait
38#include <bits/functional_hash.h>
39#include <bits/this_thread_sleep.h>
40
41#include <chrono>
42
43#ifdef _GLIBCXX_HAVE_LINUX_FUTEX
44#include <exception> // std::terminate
45#include <sys/time.h>
46#endif
47
48namespace std _GLIBCXX_VISIBILITY(default)
49{
50_GLIBCXX_BEGIN_NAMESPACE_VERSION
51
52 namespace __detail
53 {
54 using __wait_clock_t = chrono::steady_clock;
55
56 template<typename _Clock, typename _Dur>
57 __wait_clock_t::time_point
58 __to_wait_clock(const chrono::time_point<_Clock, _Dur>& __atime) noexcept
59 {
60 const typename _Clock::time_point __c_entry = _Clock::now();
61 const __wait_clock_t::time_point __w_entry = __wait_clock_t::now();
62 const auto __delta = __atime - __c_entry;
63 using __w_dur = typename __wait_clock_t::duration;
64 return __w_entry + chrono::ceil<__w_dur>(__delta);
65 }
66
67 template<typename _Dur>
68 __wait_clock_t::time_point
69 __to_wait_clock(const chrono::time_point<__wait_clock_t,
70 _Dur>& __atime) noexcept
71 {
72 using __w_dur = typename __wait_clock_t::duration;
73 return chrono::ceil<__w_dur>(__atime);
74 }
75
76#ifdef _GLIBCXX_HAVE_LINUX_FUTEX
77#define _GLIBCXX_HAVE_PLATFORM_TIMED_WAIT
78 // returns true if wait ended before timeout
79 template<typename _Dur>
80 bool
81 __platform_wait_until_impl(const __platform_wait_t* __addr,
82 __platform_wait_t __old,
83 const chrono::time_point<__wait_clock_t, _Dur>&
84 __atime) noexcept
85 {
86 auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
87 auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
88
89 struct timespec __rt =
90 {
91 static_cast<std::time_t>(__s.time_since_epoch().count()),
92 static_cast<long>(__ns.count())
93 };
94
95 auto __e = syscall (SYS_futex, __addr,
96 static_cast<int>(__futex_wait_flags::
97 __wait_bitset_private),
98 __old, &__rt, nullptr,
99 static_cast<int>(__futex_wait_flags::
100 __bitset_match_any));
101
102 if (__e)
103 {
104 if ((errno != ETIMEDOUT) && (errno != EINTR)
105 && (errno != EAGAIN))
106 __throw_system_error(errno);
107 return true;
108 }
109 return false;
110 }
111
112 // returns true if wait ended before timeout
113 template<typename _Clock, typename _Dur>
114 bool
115 __platform_wait_until(const __platform_wait_t* __addr, __platform_wait_t __old,
116 const chrono::time_point<_Clock, _Dur>& __atime)
117 {
118 if constexpr (is_same_v<__wait_clock_t, _Clock>)
119 {
120 return __platform_wait_until_impl(__addr, __old, __atime);
121 }
122 else
123 {
124 if (!__platform_wait_until_impl(__addr, __old,
125 __to_wait_clock(__atime)))
126 {
127 // We got a timeout when measured against __clock_t but
128 // we need to check against the caller-supplied clock
129 // to tell whether we should return a timeout.
130 if (_Clock::now() < __atime)
131 return true;
132 }
133 return false;
134 }
135 }
136#else
137// define _GLIBCXX_HAVE_PLATFORM_TIMED_WAIT and implement __platform_wait_until()
138// if there is a more efficient primitive supported by the platform
139// (e.g. __ulock_wait())which is better than pthread_cond_clockwait
140#endif // ! PLATFORM_TIMED_WAIT
141
142 // Returns true if wait ended before timeout.
143 // _Clock must be either steady_clock or system_clock.
144 template<typename _Clock, typename _Dur>
145 bool
146 __cond_wait_until_impl(__condvar& __cv, mutex& __mx,
147 const chrono::time_point<_Clock, _Dur>& __atime)
148 {
149 static_assert(std::__is_one_of<_Clock, chrono::steady_clock,
150 chrono::system_clock>::value);
151
152 auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
153 auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
154
155 __gthread_time_t __ts =
156 {
157 static_cast<std::time_t>(__s.time_since_epoch().count()),
158 static_cast<long>(__ns.count())
159 };
160
161#ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
162 if constexpr (is_same_v<chrono::steady_clock, _Clock>)
163 __cv.wait_until(__mx, CLOCK_MONOTONIC, __ts);
164 else
165#endif
166 __cv.wait_until(__mx, __ts);
167 return _Clock::now() < __atime;
168 }
169
170 // returns true if wait ended before timeout
171 template<typename _Clock, typename _Dur>
172 bool
173 __cond_wait_until(__condvar& __cv, mutex& __mx,
174 const chrono::time_point<_Clock, _Dur>& __atime)
175 {
176#ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
177 if constexpr (is_same_v<_Clock, chrono::steady_clock>)
178 return __detail::__cond_wait_until_impl(__cv, __mx, __atime);
179 else
180#endif
181 if constexpr (is_same_v<_Clock, chrono::system_clock>)
182 return __detail::__cond_wait_until_impl(__cv, __mx, __atime);
183 else
184 {
185 if (__cond_wait_until_impl(__cv, __mx,
186 __to_wait_clock(__atime)))
187 {
188 // We got a timeout when measured against __clock_t but
189 // we need to check against the caller-supplied clock
190 // to tell whether we should return a timeout.
191 if (_Clock::now() < __atime)
192 return true;
193 }
194 return false;
195 }
196 }
197
198 struct __timed_waiter_pool : __waiter_pool_base
199 {
200 // returns true if wait ended before timeout
201 template<typename _Clock, typename _Dur>
202 bool
203 _M_do_wait_until(__platform_wait_t* __addr, __platform_wait_t __old,
204 const chrono::time_point<_Clock, _Dur>& __atime)
205 {
206#ifdef _GLIBCXX_HAVE_PLATFORM_TIMED_WAIT
207 return __platform_wait_until(__addr, __old, __atime);
208#else
209 __platform_wait_t __val;
210 __atomic_load(__addr, &__val, __ATOMIC_RELAXED);
211 if (__val == __old)
212 {
213 lock_guard<mutex> __l(_M_mtx);
214 return __cond_wait_until(_M_cv, _M_mtx, __atime);
215 }
216#endif // _GLIBCXX_HAVE_PLATFORM_TIMED_WAIT
217 }
218 };
219
220 struct __timed_backoff_spin_policy
221 {
222 __wait_clock_t::time_point _M_deadline;
223 __wait_clock_t::time_point _M_t0;
224
225 template<typename _Clock, typename _Dur>
226 __timed_backoff_spin_policy(chrono::time_point<_Clock, _Dur>
227 __deadline = _Clock::time_point::max(),
228 chrono::time_point<_Clock, _Dur>
229 __t0 = _Clock::now()) noexcept
230 : _M_deadline(__to_wait_clock(__deadline))
231 , _M_t0(__to_wait_clock(__t0))
232 { }
233
234 bool
235 operator()() const noexcept
236 {
237 using namespace literals::chrono_literals;
238 auto __now = __wait_clock_t::now();
239 if (_M_deadline <= __now)
240 return false;
241
242 auto __elapsed = __now - _M_t0;
243 if (__elapsed > 128ms)
244 {
245 this_thread::sleep_for(64ms);
246 }
247 else if (__elapsed > 64us)
248 {
249 this_thread::sleep_for(__elapsed / 2);
250 }
251 else if (__elapsed > 4us)
252 {
253 __thread_yield();
254 }
255 else
256 return false;
257 return true;
258 }
259 };
260
261 template<typename _EntersWait>
262 struct __timed_waiter : __waiter_base<__timed_waiter_pool>
263 {
264 using __base_type = __waiter_base<__timed_waiter_pool>;
265
266 template<typename _Tp>
267 __timed_waiter(const _Tp* __addr) noexcept
268 : __base_type(__addr)
269 {
270 if constexpr (_EntersWait::value)
271 _M_w._M_enter_wait();
272 }
273
274 ~__timed_waiter()
275 {
276 if constexpr (_EntersWait::value)
277 _M_w._M_leave_wait();
278 }
279
280 // returns true if wait ended before timeout
281 template<typename _Tp, typename _ValFn,
282 typename _Clock, typename _Dur>
283 bool
284 _M_do_wait_until_v(_Tp __old, _ValFn __vfn,
285 const chrono::time_point<_Clock, _Dur>&
286 __atime) noexcept
287 {
288 __platform_wait_t __val;
289 if (_M_do_spin(__old, std::move(__vfn), __val,
290 __timed_backoff_spin_policy(__atime)))
291 return true;
292 return __base_type::_M_w._M_do_wait_until(__base_type::_M_addr, __val, __atime);
293 }
294
295 // returns true if wait ended before timeout
296 template<typename _Pred,
297 typename _Clock, typename _Dur>
298 bool
299 _M_do_wait_until(_Pred __pred, __platform_wait_t __val,
300 const chrono::time_point<_Clock, _Dur>&
301 __atime) noexcept
302 {
303 for (auto __now = _Clock::now(); __now < __atime;
304 __now = _Clock::now())
305 {
306 if (__base_type::_M_w._M_do_wait_until(
307 __base_type::_M_addr, __val, __atime)
308 && __pred())
309 return true;
310
311 if (__base_type::_M_do_spin(__pred, __val,
312 __timed_backoff_spin_policy(__atime, __now)))
313 return true;
314 }
315 return false;
316 }
317
318 // returns true if wait ended before timeout
319 template<typename _Pred,
320 typename _Clock, typename _Dur>
321 bool
322 _M_do_wait_until(_Pred __pred,
323 const chrono::time_point<_Clock, _Dur>&
324 __atime) noexcept
325 {
326 __platform_wait_t __val;
327 if (__base_type::_M_do_spin(__pred, __val,
328 __timed_backoff_spin_policy(__atime)))
329 return true;
330 return _M_do_wait_until(__pred, __val, __atime);
331 }
332
333 template<typename _Tp, typename _ValFn,
334 typename _Rep, typename _Period>
335 bool
336 _M_do_wait_for_v(_Tp __old, _ValFn __vfn,
337 const chrono::duration<_Rep, _Period>&
338 __rtime) noexcept
339 {
340 __platform_wait_t __val;
341 if (_M_do_spin_v(__old, std::move(__vfn), __val))
342 return true;
343
344 if (!__rtime.count())
345 return false; // no rtime supplied, and spin did not acquire
346
347 auto __reltime = chrono::ceil<__wait_clock_t::duration>(__rtime);
348
349 return __base_type::_M_w._M_do_wait_until(
350 __base_type::_M_addr,
351 __val,
352 chrono::steady_clock::now() + __reltime);
353 }
354
355 template<typename _Pred,
356 typename _Rep, typename _Period>
357 bool
358 _M_do_wait_for(_Pred __pred,
359 const chrono::duration<_Rep, _Period>& __rtime) noexcept
360 {
361 __platform_wait_t __val;
362 if (__base_type::_M_do_spin(__pred, __val))
363 return true;
364
365 if (!__rtime.count())
366 return false; // no rtime supplied, and spin did not acquire
367
368 auto __reltime = chrono::ceil<__wait_clock_t::duration>(__rtime);
369
370 return _M_do_wait_until(__pred, __val,
371 chrono::steady_clock::now() + __reltime);
372 }
373 };
374
375 using __enters_timed_wait = __timed_waiter<std::true_type>;
376 using __bare_timed_wait = __timed_waiter<std::false_type>;
377 } // namespace __detail
378
379 // returns true if wait ended before timeout
380 template<typename _Tp, typename _ValFn,
381 typename _Clock, typename _Dur>
382 bool
383 __atomic_wait_address_until_v(const _Tp* __addr, _Tp&& __old, _ValFn&& __vfn,
384 const chrono::time_point<_Clock, _Dur>&
385 __atime) noexcept
386 {
387 __detail::__enters_timed_wait __w{__addr};
388 return __w._M_do_wait_until_v(__old, __vfn, __atime);
389 }
390
391 template<typename _Tp, typename _Pred,
392 typename _Clock, typename _Dur>
393 bool
394 __atomic_wait_address_until(const _Tp* __addr, _Pred __pred,
395 const chrono::time_point<_Clock, _Dur>&
396 __atime) noexcept
397 {
398 __detail::__enters_timed_wait __w{__addr};
399 return __w._M_do_wait_until(__pred, __atime);
400 }
401
402 template<typename _Pred,
403 typename _Clock, typename _Dur>
404 bool
405 __atomic_wait_address_until_bare(const __detail::__platform_wait_t* __addr,
406 _Pred __pred,
407 const chrono::time_point<_Clock, _Dur>&
408 __atime) noexcept
409 {
410 __detail::__bare_timed_wait __w{__addr};
411 return __w._M_do_wait_until(__pred, __atime);
412 }
413
414 template<typename _Tp, typename _ValFn,
415 typename _Rep, typename _Period>
416 bool
417 __atomic_wait_address_for_v(const _Tp* __addr, _Tp&& __old, _ValFn&& __vfn,
418 const chrono::duration<_Rep, _Period>& __rtime) noexcept
419 {
420 __detail::__enters_timed_wait __w{__addr};
421 return __w._M_do_wait_for_v(__old, __vfn, __rtime);
422 }
423
424 template<typename _Tp, typename _Pred,
425 typename _Rep, typename _Period>
426 bool
427 __atomic_wait_address_for(const _Tp* __addr, _Pred __pred,
428 const chrono::duration<_Rep, _Period>& __rtime) noexcept
429 {
430
431 __detail::__enters_timed_wait __w{__addr};
432 return __w._M_do_wait_for(__pred, __rtime);
433 }
434
435 template<typename _Pred,
436 typename _Rep, typename _Period>
437 bool
438 __atomic_wait_address_for_bare(const __detail::__platform_wait_t* __addr,
439 _Pred __pred,
440 const chrono::duration<_Rep, _Period>& __rtime) noexcept
441 {
442 __detail::__bare_timed_wait __w{__addr};
443 return __w._M_do_wait_for(__pred, __rtime);
444 }
445_GLIBCXX_END_NAMESPACE_VERSION
446} // namespace std
447#endif // __cpp_lib_atomic_wait
448#endif // _GLIBCXX_ATOMIC_TIMED_WAIT_H
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