e05ff30078
The fix for PR68519 in 83fd5e73b3 only
applied to condition_variable::wait_for. This problem can also apply to
condition_variable::wait_until but only if the custom clock is using a
more recent epoch so that a small enough delta can be calculated. let's
use the newly-added chrono::__detail::ceil to fix this and also make use
of that function to simplify the previous wait_for fixes.
Also, simplify the existing test case for PR68519 a little and make its
variables local so we can add a new test case for the above problem.
Unfortunately, the test would have only started failing if sufficient
time has passed since the chrono::steady_clock epoch had passed anyway,
but it's better than nothing.
libstdc++-v3/ChangeLog:
* include/std/condition_variable (condition_variable::wait_until):
Convert delta to steady_clock duration before adding to current
steady_clock time to avoid rounding errors described in PR68519.
(condition_variable::wait_for): Simplify calculation of absolute
time by using chrono::__detail::ceil in both overloads.
* testsuite/30_threads/condition_variable/members/68519.cc:
(test_wait_for): Renamed from test01. Replace unassigned val
variable with constant false. Reduce scope of mx and cv
variables to just test_wait_for function.
(test_wait_until): Add new test case.
463 lines
13 KiB
C++
463 lines
13 KiB
C++
// <condition_variable> -*- C++ -*-
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// Copyright (C) 2008-2020 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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// 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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// 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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// 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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/** @file include/condition_variable
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* This is a Standard C++ Library header.
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*/
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#ifndef _GLIBCXX_CONDITION_VARIABLE
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#define _GLIBCXX_CONDITION_VARIABLE 1
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#pragma GCC system_header
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#if __cplusplus < 201103L
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# include <bits/c++0x_warning.h>
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#else
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#include <chrono>
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#include <bits/std_mutex.h>
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#include <bits/unique_lock.h>
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#include <ext/concurrence.h>
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#include <bits/alloc_traits.h>
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#include <bits/allocator.h>
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#include <bits/unique_ptr.h>
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#include <bits/shared_ptr.h>
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#include <bits/cxxabi_forced.h>
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#if __cplusplus > 201703L
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# include <stop_token>
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#endif
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#if defined(_GLIBCXX_HAS_GTHREADS)
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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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* @defgroup condition_variables Condition Variables
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* @ingroup concurrency
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*
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* Classes for condition_variable support.
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* @{
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*/
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/// cv_status
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enum class cv_status { no_timeout, timeout };
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/// condition_variable
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class condition_variable
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{
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using steady_clock = chrono::steady_clock;
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using system_clock = chrono::system_clock;
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#ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
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using __clock_t = steady_clock;
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#else
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using __clock_t = system_clock;
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#endif
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typedef __gthread_cond_t __native_type;
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#ifdef __GTHREAD_COND_INIT
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__native_type _M_cond = __GTHREAD_COND_INIT;
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#else
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__native_type _M_cond;
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#endif
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public:
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typedef __native_type* native_handle_type;
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condition_variable() noexcept;
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~condition_variable() noexcept;
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condition_variable(const condition_variable&) = delete;
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condition_variable& operator=(const condition_variable&) = delete;
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void
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notify_one() noexcept;
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void
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notify_all() noexcept;
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void
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wait(unique_lock<mutex>& __lock) noexcept;
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template<typename _Predicate>
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void
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wait(unique_lock<mutex>& __lock, _Predicate __p)
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{
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while (!__p())
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wait(__lock);
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}
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#ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
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template<typename _Duration>
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cv_status
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wait_until(unique_lock<mutex>& __lock,
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const chrono::time_point<steady_clock, _Duration>& __atime)
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{ return __wait_until_impl(__lock, __atime); }
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#endif
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template<typename _Duration>
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cv_status
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wait_until(unique_lock<mutex>& __lock,
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const chrono::time_point<system_clock, _Duration>& __atime)
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{ return __wait_until_impl(__lock, __atime); }
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template<typename _Clock, typename _Duration>
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cv_status
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wait_until(unique_lock<mutex>& __lock,
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const chrono::time_point<_Clock, _Duration>& __atime)
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{
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#if __cplusplus > 201703L
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static_assert(chrono::is_clock_v<_Clock>);
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#endif
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using __s_dur = typename __clock_t::duration;
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const typename _Clock::time_point __c_entry = _Clock::now();
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const __clock_t::time_point __s_entry = __clock_t::now();
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const auto __delta = __atime - __c_entry;
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const auto __s_atime = __s_entry +
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chrono::__detail::ceil<__s_dur>(__delta);
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if (__wait_until_impl(__lock, __s_atime) == cv_status::no_timeout)
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return cv_status::no_timeout;
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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 cv_status::no_timeout;
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return cv_status::timeout;
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}
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template<typename _Clock, typename _Duration, typename _Predicate>
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bool
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wait_until(unique_lock<mutex>& __lock,
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const chrono::time_point<_Clock, _Duration>& __atime,
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_Predicate __p)
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{
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while (!__p())
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if (wait_until(__lock, __atime) == cv_status::timeout)
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return __p();
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return true;
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}
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template<typename _Rep, typename _Period>
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cv_status
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wait_for(unique_lock<mutex>& __lock,
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const chrono::duration<_Rep, _Period>& __rtime)
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{
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using __dur = typename steady_clock::duration;
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return wait_until(__lock,
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steady_clock::now() +
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chrono::__detail::ceil<__dur>(__rtime));
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}
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template<typename _Rep, typename _Period, typename _Predicate>
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bool
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wait_for(unique_lock<mutex>& __lock,
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const chrono::duration<_Rep, _Period>& __rtime,
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_Predicate __p)
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{
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using __dur = typename steady_clock::duration;
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return wait_until(__lock,
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steady_clock::now() +
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chrono::__detail::ceil<__dur>(__rtime),
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std::move(__p));
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}
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native_handle_type
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native_handle()
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{ return &_M_cond; }
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private:
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#ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
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template<typename _Dur>
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cv_status
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__wait_until_impl(unique_lock<mutex>& __lock,
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const chrono::time_point<steady_clock, _Dur>& __atime)
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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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__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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pthread_cond_clockwait(&_M_cond, __lock.mutex()->native_handle(),
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CLOCK_MONOTONIC,
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&__ts);
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return (steady_clock::now() < __atime
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? cv_status::no_timeout : cv_status::timeout);
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}
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#endif
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template<typename _Dur>
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cv_status
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__wait_until_impl(unique_lock<mutex>& __lock,
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const chrono::time_point<system_clock, _Dur>& __atime)
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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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__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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__gthread_cond_timedwait(&_M_cond, __lock.mutex()->native_handle(),
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&__ts);
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return (system_clock::now() < __atime
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? cv_status::no_timeout : cv_status::timeout);
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}
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};
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void
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notify_all_at_thread_exit(condition_variable&, unique_lock<mutex>);
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struct __at_thread_exit_elt
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{
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__at_thread_exit_elt* _M_next;
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void (*_M_cb)(void*);
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};
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inline namespace _V2 {
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/// condition_variable_any
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// Like above, but mutex is not required to have try_lock.
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class condition_variable_any
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{
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#ifdef _GLIBCXX_USE_PTHREAD_COND_CLOCKWAIT
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using __clock_t = chrono::steady_clock;
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#else
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using __clock_t = chrono::system_clock;
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#endif
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condition_variable _M_cond;
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shared_ptr<mutex> _M_mutex;
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// scoped unlock - unlocks in ctor, re-locks in dtor
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template<typename _Lock>
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struct _Unlock
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{
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explicit _Unlock(_Lock& __lk) : _M_lock(__lk) { __lk.unlock(); }
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
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~_Unlock() noexcept(false)
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{
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if (uncaught_exception())
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{
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__try
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{ _M_lock.lock(); }
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__catch(const __cxxabiv1::__forced_unwind&)
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{ __throw_exception_again; }
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__catch(...)
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{ }
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}
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else
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_M_lock.lock();
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}
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#pragma GCC diagnostic pop
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_Unlock(const _Unlock&) = delete;
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_Unlock& operator=(const _Unlock&) = delete;
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_Lock& _M_lock;
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};
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public:
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condition_variable_any() : _M_mutex(std::make_shared<mutex>()) { }
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~condition_variable_any() = default;
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condition_variable_any(const condition_variable_any&) = delete;
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condition_variable_any& operator=(const condition_variable_any&) = delete;
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void
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notify_one() noexcept
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{
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lock_guard<mutex> __lock(*_M_mutex);
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_M_cond.notify_one();
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}
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void
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notify_all() noexcept
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{
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lock_guard<mutex> __lock(*_M_mutex);
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_M_cond.notify_all();
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}
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template<typename _Lock>
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void
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wait(_Lock& __lock)
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{
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shared_ptr<mutex> __mutex = _M_mutex;
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unique_lock<mutex> __my_lock(*__mutex);
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_Unlock<_Lock> __unlock(__lock);
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// *__mutex must be unlocked before re-locking __lock so move
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// ownership of *__mutex lock to an object with shorter lifetime.
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unique_lock<mutex> __my_lock2(std::move(__my_lock));
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_M_cond.wait(__my_lock2);
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}
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template<typename _Lock, typename _Predicate>
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void
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wait(_Lock& __lock, _Predicate __p)
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{
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while (!__p())
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wait(__lock);
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}
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template<typename _Lock, typename _Clock, typename _Duration>
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cv_status
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wait_until(_Lock& __lock,
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const chrono::time_point<_Clock, _Duration>& __atime)
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{
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shared_ptr<mutex> __mutex = _M_mutex;
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unique_lock<mutex> __my_lock(*__mutex);
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_Unlock<_Lock> __unlock(__lock);
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// *__mutex must be unlocked before re-locking __lock so move
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// ownership of *__mutex lock to an object with shorter lifetime.
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unique_lock<mutex> __my_lock2(std::move(__my_lock));
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return _M_cond.wait_until(__my_lock2, __atime);
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}
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template<typename _Lock, typename _Clock,
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typename _Duration, typename _Predicate>
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bool
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wait_until(_Lock& __lock,
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const chrono::time_point<_Clock, _Duration>& __atime,
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_Predicate __p)
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{
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while (!__p())
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if (wait_until(__lock, __atime) == cv_status::timeout)
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return __p();
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return true;
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}
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template<typename _Lock, typename _Rep, typename _Period>
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cv_status
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wait_for(_Lock& __lock, const chrono::duration<_Rep, _Period>& __rtime)
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{ return wait_until(__lock, __clock_t::now() + __rtime); }
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template<typename _Lock, typename _Rep,
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typename _Period, typename _Predicate>
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bool
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wait_for(_Lock& __lock,
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const chrono::duration<_Rep, _Period>& __rtime, _Predicate __p)
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{ return wait_until(__lock, __clock_t::now() + __rtime, std::move(__p)); }
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#ifdef __cpp_lib_jthread
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template <class _Lock, class _Predicate>
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bool wait(_Lock& __lock,
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stop_token __stoken,
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_Predicate __p)
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{
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if (__stoken.stop_requested())
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{
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return __p();
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}
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std::stop_callback __cb(__stoken, [this] { notify_all(); });
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shared_ptr<mutex> __mutex = _M_mutex;
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while (!__p())
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{
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unique_lock<mutex> __my_lock(*__mutex);
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if (__stoken.stop_requested())
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{
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return false;
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}
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// *__mutex must be unlocked before re-locking __lock so move
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// ownership of *__mutex lock to an object with shorter lifetime.
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_Unlock<_Lock> __unlock(__lock);
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unique_lock<mutex> __my_lock2(std::move(__my_lock));
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_M_cond.wait(__my_lock2);
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}
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return true;
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}
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template <class _Lock, class _Clock, class _Duration, class _Predicate>
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bool wait_until(_Lock& __lock,
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stop_token __stoken,
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const chrono::time_point<_Clock, _Duration>& __abs_time,
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_Predicate __p)
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{
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if (__stoken.stop_requested())
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{
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return __p();
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}
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std::stop_callback __cb(__stoken, [this] { notify_all(); });
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shared_ptr<mutex> __mutex = _M_mutex;
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while (!__p())
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{
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bool __stop;
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{
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unique_lock<mutex> __my_lock(*__mutex);
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if (__stoken.stop_requested())
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{
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return false;
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}
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_Unlock<_Lock> __u(__lock);
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unique_lock<mutex> __my_lock2(std::move(__my_lock));
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const auto __status = _M_cond.wait_until(__my_lock2, __abs_time);
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__stop = (__status == std::cv_status::timeout) || __stoken.stop_requested();
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}
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if (__stop)
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{
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return __p();
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}
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}
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return true;
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}
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template <class _Lock, class _Rep, class _Period, class _Predicate>
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bool wait_for(_Lock& __lock,
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stop_token __stoken,
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const chrono::duration<_Rep, _Period>& __rel_time,
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_Predicate __p)
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{
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auto __abst = std::chrono::steady_clock::now() + __rel_time;
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return wait_until(__lock,
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std::move(__stoken),
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__abst,
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std::move(__p));
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}
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#endif
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};
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} // end inline namespace
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// @} group condition_variables
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_GLIBCXX_END_NAMESPACE_VERSION
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} // namespace
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#endif // _GLIBCXX_HAS_GTHREADS
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#endif // C++11
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#endif // _GLIBCXX_CONDITION_VARIABLE
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