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// -*- C++ -*- header. |
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|
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// Copyright (C) 2020-2021 Free Software Foundation, Inc. |
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// |
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// This file is part of the GNU ISO C++ Library. This library is free |
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// software; you can redistribute it and/or modify it under the |
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// terms of the GNU General Public License as published by the |
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// Free Software Foundation; either version 3, or (at your option) |
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// any later version. |
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|
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// This library is distributed in the hope that it will be useful, |
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// but WITHOUT ANY WARRANTY; without even the implied warranty of |
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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// GNU General Public License for more details. |
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|
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// Under Section 7 of GPL version 3, you are granted additional |
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// permissions described in the GCC Runtime Library Exception, version |
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// 3.1, as published by the Free Software Foundation. |
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|
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// You should have received a copy of the GNU General Public License and |
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// a copy of the GCC Runtime Library Exception along with this program; |
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see |
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// <http://www.gnu.org/licenses/>. |
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|
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/** @file bits/atomic_timed_wait.h |
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* This is an internal header file, included by other library headers. |
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* Do not attempt to use it directly. @headername{atomic} |
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*/ |
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|
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#ifndef _GLIBCXX_ATOMIC_TIMED_WAIT_H |
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#define _GLIBCXX_ATOMIC_TIMED_WAIT_H 1 |
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|
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#pragma GCC system_header |
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|
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#include <bits/atomic_wait.h> |
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|
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#if __cpp_lib_atomic_wait |
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#include <bits/functional_hash.h> |
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#include <bits/this_thread_sleep.h> |
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|
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#include <chrono> |
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|
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#ifdef _GLIBCXX_HAVE_LINUX_FUTEX |
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#include <exception> // std::terminate |
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#include <sys/time.h> |
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#endif |
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|
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namespace std _GLIBCXX_VISIBILITY(default) |
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{ |
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_GLIBCXX_BEGIN_NAMESPACE_VERSION |
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|
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namespace __detail |
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{ |
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using __wait_clock_t = chrono::steady_clock; |
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|
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template<typename _Clock, typename _Dur> |
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__wait_clock_t::time_point |
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__to_wait_clock(const chrono::time_point<_Clock, _Dur>& __atime) noexcept |
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{ |
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const typename _Clock::time_point __c_entry = _Clock::now(); |
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const __wait_clock_t::time_point __w_entry = __wait_clock_t::now(); |
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const auto __delta = __atime - __c_entry; |
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using __w_dur = typename __wait_clock_t::duration; |
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return __w_entry + chrono::ceil<__w_dur>(__delta); |
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} |
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|
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template<typename _Dur> |
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__wait_clock_t::time_point |
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__to_wait_clock(const chrono::time_point<__wait_clock_t, |
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_Dur>& __atime) noexcept |
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{ |
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using __w_dur = typename __wait_clock_t::duration; |
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return chrono::ceil<__w_dur>(__atime); |
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} |
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|
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#ifdef _GLIBCXX_HAVE_LINUX_FUTEX |
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#define _GLIBCXX_HAVE_PLATFORM_TIMED_WAIT |
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// returns true if wait ended before timeout |
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template<typename _Dur> |
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bool |
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__platform_wait_until_impl(const __platform_wait_t* __addr, |
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__platform_wait_t __old, |
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const chrono::time_point<__wait_clock_t, _Dur>& |
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__atime) noexcept |
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{ |
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auto __s = chrono::time_point_cast<chrono::seconds>(__atime); |
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auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s); |
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|
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struct timespec __rt = |
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{ |
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static_cast<std::time_t>(__s.time_since_epoch().count()), |
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static_cast<long>(__ns.count()) |
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}; |
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|
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auto __e = syscall (SYS_futex, __addr, |
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static_cast<int>(__futex_wait_flags:: |
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__wait_bitset_private), |
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__old, &__rt, nullptr, |
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static_cast<int>(__futex_wait_flags:: |
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__bitset_match_any)); |
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|
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if (__e) |
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{ |
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if ((errno != ETIMEDOUT) && (errno != EINTR) |
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&& (errno != EAGAIN)) |
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__throw_system_error(errno); |
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return true; |
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} |
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return false; |
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} |
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|
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// returns true if wait ended before timeout |
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template<typename _Clock, typename _Dur> |
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bool |
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__platform_wait_until(const __platform_wait_t* __addr, __platform_wait_t __old, |
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const chrono::time_point<_Clock, _Dur>& __atime) |
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{ |
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if constexpr (is_same_v<__wait_clock_t, _Clock>) |
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{ |
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return __platform_wait_until_impl(__addr, __old, __atime); |
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} |
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else |
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{ |
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if (!__platform_wait_until_impl(__addr, __old, |
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__to_wait_clock(__atime))) |
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{ |
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// We got a timeout when measured against __clock_t but |
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// we need to check against the caller-supplied clock |
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// to tell whether we should return a timeout. |
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if (_Clock::now() < __atime) |
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return true; |
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} |
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return false; |
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} |
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} |
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#else |
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// define _GLIBCXX_HAVE_PLATFORM_TIMED_WAIT and implement __platform_wait_until() |
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// if there is a more efficient primitive supported by the platform |
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// (e.g. __ulock_wait())which is better than pthread_cond_clockwait |
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#endif // ! PLATFORM_TIMED_WAIT |
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|
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// Returns true if wait ended before timeout. |
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// _Clock must be either steady_clock or system_clock. |
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template<typename _Clock, typename _Dur> |
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bool |
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__cond_wait_until_impl(__condvar& __cv, mutex& __mx, |
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const chrono::time_point<_Clock, _Dur>& __atime) |
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{ |
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static_assert(std::__is_one_of<_Clock, chrono::steady_clock, |
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chrono::system_clock>::value); |
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|
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auto __s = chrono::time_point_cast<chrono::seconds>(__atime); |
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auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s); |
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|
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__gthread_time_t __ts = |
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{ |
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static_cast<std::time_t>(__s.time_since_epoch().count()), |
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static_cast<long>(__ns.count()) |
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}; |
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|
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#ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT |
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if constexpr (is_same_v<chrono::steady_clock, _Clock>) |
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__cv.wait_until(__mx, CLOCK_MONOTONIC, __ts); |
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else |
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#endif |
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__cv.wait_until(__mx, __ts); |
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return _Clock::now() < __atime; |
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} |
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|
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// returns true if wait ended before timeout |
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template<typename _Clock, typename _Dur> |
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bool |
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__cond_wait_until(__condvar& __cv, mutex& __mx, |
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const chrono::time_point<_Clock, _Dur>& __atime) |
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{ |
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#ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT |
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if constexpr (is_same_v<_Clock, chrono::steady_clock>) |
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return __detail::__cond_wait_until_impl(__cv, __mx, __atime); |
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else |
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#endif |
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if constexpr (is_same_v<_Clock, chrono::system_clock>) |
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return __detail::__cond_wait_until_impl(__cv, __mx, __atime); |
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else |
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{ |
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if (__cond_wait_until_impl(__cv, __mx, |
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__to_wait_clock(__atime))) |
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{ |
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// We got a timeout when measured against __clock_t but |
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// we need to check against the caller-supplied clock |
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// to tell whether we should return a timeout. |
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if (_Clock::now() < __atime) |
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return true; |
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} |
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return false; |
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} |
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} |
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|
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struct __timed_waiter_pool : __waiter_pool_base |
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{ |
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// returns true if wait ended before timeout |
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template<typename _Clock, typename _Dur> |
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bool |
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_M_do_wait_until(__platform_wait_t* __addr, __platform_wait_t __old, |
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const chrono::time_point<_Clock, _Dur>& __atime) |
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{ |
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#ifdef _GLIBCXX_HAVE_PLATFORM_TIMED_WAIT |
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return __platform_wait_until(__addr, __old, __atime); |
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#else |
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__platform_wait_t __val; |
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__atomic_load(__addr, &__val, __ATOMIC_RELAXED); |
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if (__val == __old) |
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{ |
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lock_guard<mutex> __l(_M_mtx); |
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return __cond_wait_until(_M_cv, _M_mtx, __atime); |
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} |
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#endif // _GLIBCXX_HAVE_PLATFORM_TIMED_WAIT |
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} |
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}; |
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|
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struct __timed_backoff_spin_policy |
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{ |
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__wait_clock_t::time_point _M_deadline; |
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__wait_clock_t::time_point _M_t0; |
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|
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template<typename _Clock, typename _Dur> |
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__timed_backoff_spin_policy(chrono::time_point<_Clock, _Dur> |
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__deadline = _Clock::time_point::max(), |
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chrono::time_point<_Clock, _Dur> |
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__t0 = _Clock::now()) noexcept |
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: _M_deadline(__to_wait_clock(__deadline)) |
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, _M_t0(__to_wait_clock(__t0)) |
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{ } |
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|
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bool |
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operator()() const noexcept |
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{ |
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using namespace literals::chrono_literals; |
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auto __now = __wait_clock_t::now(); |
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if (_M_deadline <= __now) |
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return false; |
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|
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auto __elapsed = __now - _M_t0; |
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if (__elapsed > 128ms) |
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{ |
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this_thread::sleep_for(64ms); |
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} |
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else if (__elapsed > 64us) |
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{ |
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this_thread::sleep_for(__elapsed / 2); |
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} |
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else if (__elapsed > 4us) |
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{ |
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__thread_yield(); |
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} |
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else |
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return false; |
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return true; |
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} |
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}; |
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|
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template<typename _EntersWait> |
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struct __timed_waiter : __waiter_base<__timed_waiter_pool> |
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{ |
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using __base_type = __waiter_base<__timed_waiter_pool>; |
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|
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template<typename _Tp> |
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__timed_waiter(const _Tp* __addr) noexcept |
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: __base_type(__addr) |
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{ |
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if constexpr (_EntersWait::value) |
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_M_w._M_enter_wait(); |
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} |
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|
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~__timed_waiter() |
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{ |
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if constexpr (_EntersWait::value) |
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_M_w._M_leave_wait(); |
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} |
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|
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// returns true if wait ended before timeout |
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template<typename _Tp, typename _ValFn, |
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typename _Clock, typename _Dur> |
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bool |
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_M_do_wait_until_v(_Tp __old, _ValFn __vfn, |
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const chrono::time_point<_Clock, _Dur>& |
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__atime) noexcept |
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{ |
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__platform_wait_t __val; |
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if (_M_do_spin(__old, std::move(__vfn), __val, |
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__timed_backoff_spin_policy(__atime))) |
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return true; |
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return __base_type::_M_w._M_do_wait_until(__base_type::_M_addr, __val, __atime); |
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} |
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|
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// returns true if wait ended before timeout |
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template<typename _Pred, |
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typename _Clock, typename _Dur> |
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bool |
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_M_do_wait_until(_Pred __pred, __platform_wait_t __val, |
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const chrono::time_point<_Clock, _Dur>& |
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__atime) noexcept |
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{ |
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for (auto __now = _Clock::now(); __now < __atime; |
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__now = _Clock::now()) |
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{ |
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if (__base_type::_M_w._M_do_wait_until( |
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__base_type::_M_addr, __val, __atime) |
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&& __pred()) |
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return true; |
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|
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if (__base_type::_M_do_spin(__pred, __val, |
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__timed_backoff_spin_policy(__atime, __now))) |
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return true; |
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} |
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return false; |
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} |
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|
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// returns true if wait ended before timeout |
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template<typename _Pred, |
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typename _Clock, typename _Dur> |
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bool |
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_M_do_wait_until(_Pred __pred, |
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const chrono::time_point<_Clock, _Dur>& |
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__atime) noexcept |
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{ |
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__platform_wait_t __val; |
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if (__base_type::_M_do_spin(__pred, __val, |
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__timed_backoff_spin_policy(__atime))) |
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return true; |
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return _M_do_wait_until(__pred, __val, __atime); |
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} |
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|
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template<typename _Tp, typename _ValFn, |
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typename _Rep, typename _Period> |
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bool |
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_M_do_wait_for_v(_Tp __old, _ValFn __vfn, |
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const chrono::duration<_Rep, _Period>& |
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__rtime) noexcept |
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{ |
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__platform_wait_t __val; |
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if (_M_do_spin_v(__old, std::move(__vfn), __val)) |
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return true; |
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|
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if (!__rtime.count()) |
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return false; // no rtime supplied, and spin did not acquire |
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|
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auto __reltime = chrono::ceil<__wait_clock_t::duration>(__rtime); |
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|
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return __base_type::_M_w._M_do_wait_until( |
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__base_type::_M_addr, |
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__val, |
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chrono::steady_clock::now() + __reltime); |
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} |
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|
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template<typename _Pred, |
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typename _Rep, typename _Period> |
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bool |
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_M_do_wait_for(_Pred __pred, |
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const chrono::duration<_Rep, _Period>& __rtime) noexcept |
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{ |
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__platform_wait_t __val; |
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if (__base_type::_M_do_spin(__pred, __val)) |
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return true; |
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|
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if (!__rtime.count()) |
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return false; // no rtime supplied, and spin did not acquire |
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|
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auto __reltime = chrono::ceil<__wait_clock_t::duration>(__rtime); |
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|
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return _M_do_wait_until(__pred, __val, |
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chrono::steady_clock::now() + __reltime); |
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} |
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}; |
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|
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using __enters_timed_wait = __timed_waiter<std::true_type>; |
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using __bare_timed_wait = __timed_waiter<std::false_type>; |
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} // namespace __detail |
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|
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// returns true if wait ended before timeout |
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template<typename _Tp, typename _ValFn, |
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typename _Clock, typename _Dur> |
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bool |
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__atomic_wait_address_until_v(const _Tp* __addr, _Tp&& __old, _ValFn&& __vfn, |
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const chrono::time_point<_Clock, _Dur>& |
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__atime) noexcept |
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{ |
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__detail::__enters_timed_wait __w{__addr}; |
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return __w._M_do_wait_until_v(__old, __vfn, __atime); |
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} |
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|
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template<typename _Tp, typename _Pred, |
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typename _Clock, typename _Dur> |
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bool |
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__atomic_wait_address_until(const _Tp* __addr, _Pred __pred, |
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const chrono::time_point<_Clock, _Dur>& |
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__atime) noexcept |
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{ |
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__detail::__enters_timed_wait __w{__addr}; |
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return __w._M_do_wait_until(__pred, __atime); |
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} |
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|
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template<typename _Pred, |
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typename _Clock, typename _Dur> |
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bool |
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__atomic_wait_address_until_bare(const __detail::__platform_wait_t* __addr, |
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_Pred __pred, |
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const chrono::time_point<_Clock, _Dur>& |
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__atime) noexcept |
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{ |
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__detail::__bare_timed_wait __w{__addr}; |
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return __w._M_do_wait_until(__pred, __atime); |
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} |
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|
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template<typename _Tp, typename _ValFn, |
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typename _Rep, typename _Period> |
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bool |
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__atomic_wait_address_for_v(const _Tp* __addr, _Tp&& __old, _ValFn&& __vfn, |
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const chrono::duration<_Rep, _Period>& __rtime) noexcept |
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{ |
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__detail::__enters_timed_wait __w{__addr}; |
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return __w._M_do_wait_for_v(__old, __vfn, __rtime); |
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} |
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|
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template<typename _Tp, typename _Pred, |
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typename _Rep, typename _Period> |
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bool |
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__atomic_wait_address_for(const _Tp* __addr, _Pred __pred, |
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const chrono::duration<_Rep, _Period>& __rtime) noexcept |
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{ |
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|
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__detail::__enters_timed_wait __w{__addr}; |
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return __w._M_do_wait_for(__pred, __rtime); |
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} |
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|
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template<typename _Pred, |
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typename _Rep, typename _Period> |
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bool |
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__atomic_wait_address_for_bare(const __detail::__platform_wait_t* __addr, |
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_Pred __pred, |
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const chrono::duration<_Rep, _Period>& __rtime) noexcept |
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{ |
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__detail::__bare_timed_wait __w{__addr}; |
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return __w._M_do_wait_for(__pred, __rtime); |
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} |
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_GLIBCXX_END_NAMESPACE_VERSION |
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} // namespace std |
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#endif // __cpp_lib_atomic_wait |
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#endif // _GLIBCXX_ATOMIC_TIMED_WAIT_H |
