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The <condition_variable> header is not small, so <shared_mutex> should not include it unless it actually needs std::condition_variable, which is only the case when we don't have pthread_rwlock_t and the POSIX Timers option. The <shared_mutex> header would be even smaller if we had a header for std::condition_variable (separate from std::condition_variable_any). That's already planned for a future change. And <memory_resource> would be even smaller if it was possible to get std::shared_mutex without std::shared_timed_mutex (which depends on <chrono>). For that to be effective, the synchronized_pool_resource would have to create its own simpler version of std::shared_lock without the timed waiting functions. I have no plans to do that. libstdc++-v3/ChangeLog: * include/std/shared_mutex: Only include <condition_variable> when pthread_rwlock_t and POSIX timers are not available. (__cpp_lib_shared_mutex, __cpp_lib_shared_timed_mutex): Change value to be type 'long'. * include/std/version (__cpp_lib_shared_mutex) (__cpp_lib_shared_timed_mutex): Likewise.
861 lines
24 KiB
C++
861 lines
24 KiB
C++
// <shared_mutex> -*- C++ -*-
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// Copyright (C) 2013-2020 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/shared_mutex
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* This is a Standard C++ Library header.
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*/
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#ifndef _GLIBCXX_SHARED_MUTEX
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#define _GLIBCXX_SHARED_MUTEX 1
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#pragma GCC system_header
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#if __cplusplus >= 201402L
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#include <chrono>
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#include <bits/functexcept.h>
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#include <bits/move.h> // move, __exchange
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#include <bits/std_mutex.h> // defer_lock_t
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#if ! (_GLIBCXX_USE_PTHREAD_RWLOCK_T && _GTHREAD_USE_MUTEX_TIMEDLOCK)
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# include <condition_variable>
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#endif
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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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* @addtogroup mutexes
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* @{
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*/
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#ifdef _GLIBCXX_HAS_GTHREADS
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#if __cplusplus >= 201703L
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#define __cpp_lib_shared_mutex 201505L
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class shared_mutex;
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#endif
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#define __cpp_lib_shared_timed_mutex 201402L
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class shared_timed_mutex;
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/// @cond undocumented
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#if _GLIBCXX_USE_PTHREAD_RWLOCK_T
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#ifdef __gthrw
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#define _GLIBCXX_GTHRW(name) \
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__gthrw(pthread_ ## name); \
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static inline int \
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__glibcxx_ ## name (pthread_rwlock_t *__rwlock) \
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{ \
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if (__gthread_active_p ()) \
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return __gthrw_(pthread_ ## name) (__rwlock); \
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else \
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return 0; \
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}
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_GLIBCXX_GTHRW(rwlock_rdlock)
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_GLIBCXX_GTHRW(rwlock_tryrdlock)
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_GLIBCXX_GTHRW(rwlock_wrlock)
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_GLIBCXX_GTHRW(rwlock_trywrlock)
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_GLIBCXX_GTHRW(rwlock_unlock)
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# ifndef PTHREAD_RWLOCK_INITIALIZER
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_GLIBCXX_GTHRW(rwlock_destroy)
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__gthrw(pthread_rwlock_init);
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static inline int
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__glibcxx_rwlock_init (pthread_rwlock_t *__rwlock)
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{
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if (__gthread_active_p ())
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return __gthrw_(pthread_rwlock_init) (__rwlock, NULL);
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else
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return 0;
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}
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# endif
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# if _GTHREAD_USE_MUTEX_TIMEDLOCK
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__gthrw(pthread_rwlock_timedrdlock);
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static inline int
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__glibcxx_rwlock_timedrdlock (pthread_rwlock_t *__rwlock,
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const timespec *__ts)
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{
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if (__gthread_active_p ())
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return __gthrw_(pthread_rwlock_timedrdlock) (__rwlock, __ts);
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else
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return 0;
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}
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__gthrw(pthread_rwlock_timedwrlock);
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static inline int
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__glibcxx_rwlock_timedwrlock (pthread_rwlock_t *__rwlock,
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const timespec *__ts)
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{
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if (__gthread_active_p ())
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return __gthrw_(pthread_rwlock_timedwrlock) (__rwlock, __ts);
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else
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return 0;
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}
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# endif
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#else
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static inline int
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__glibcxx_rwlock_rdlock (pthread_rwlock_t *__rwlock)
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{ return pthread_rwlock_rdlock (__rwlock); }
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static inline int
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__glibcxx_rwlock_tryrdlock (pthread_rwlock_t *__rwlock)
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{ return pthread_rwlock_tryrdlock (__rwlock); }
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static inline int
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__glibcxx_rwlock_wrlock (pthread_rwlock_t *__rwlock)
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{ return pthread_rwlock_wrlock (__rwlock); }
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static inline int
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__glibcxx_rwlock_trywrlock (pthread_rwlock_t *__rwlock)
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{ return pthread_rwlock_trywrlock (__rwlock); }
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static inline int
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__glibcxx_rwlock_unlock (pthread_rwlock_t *__rwlock)
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{ return pthread_rwlock_unlock (__rwlock); }
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static inline int
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__glibcxx_rwlock_destroy(pthread_rwlock_t *__rwlock)
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{ return pthread_rwlock_destroy (__rwlock); }
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static inline int
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__glibcxx_rwlock_init(pthread_rwlock_t *__rwlock)
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{ return pthread_rwlock_init (__rwlock, NULL); }
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# if _GTHREAD_USE_MUTEX_TIMEDLOCK
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static inline int
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__glibcxx_rwlock_timedrdlock (pthread_rwlock_t *__rwlock,
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const timespec *__ts)
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{ return pthread_rwlock_timedrdlock (__rwlock, __ts); }
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static inline int
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__glibcxx_rwlock_timedwrlock (pthread_rwlock_t *__rwlock,
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const timespec *__ts)
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{ return pthread_rwlock_timedwrlock (__rwlock, __ts); }
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# endif
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#endif
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/// A shared mutex type implemented using pthread_rwlock_t.
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class __shared_mutex_pthread
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{
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friend class shared_timed_mutex;
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#ifdef PTHREAD_RWLOCK_INITIALIZER
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pthread_rwlock_t _M_rwlock = PTHREAD_RWLOCK_INITIALIZER;
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public:
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__shared_mutex_pthread() = default;
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~__shared_mutex_pthread() = default;
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#else
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pthread_rwlock_t _M_rwlock;
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public:
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__shared_mutex_pthread()
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{
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int __ret = __glibcxx_rwlock_init(&_M_rwlock);
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if (__ret == ENOMEM)
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__throw_bad_alloc();
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else if (__ret == EAGAIN)
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__throw_system_error(int(errc::resource_unavailable_try_again));
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else if (__ret == EPERM)
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__throw_system_error(int(errc::operation_not_permitted));
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// Errors not handled: EBUSY, EINVAL
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__glibcxx_assert(__ret == 0);
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}
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~__shared_mutex_pthread()
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{
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int __ret __attribute((__unused__)) = __glibcxx_rwlock_destroy(&_M_rwlock);
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// Errors not handled: EBUSY, EINVAL
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__glibcxx_assert(__ret == 0);
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}
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#endif
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__shared_mutex_pthread(const __shared_mutex_pthread&) = delete;
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__shared_mutex_pthread& operator=(const __shared_mutex_pthread&) = delete;
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void
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lock()
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{
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int __ret = __glibcxx_rwlock_wrlock(&_M_rwlock);
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if (__ret == EDEADLK)
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__throw_system_error(int(errc::resource_deadlock_would_occur));
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// Errors not handled: EINVAL
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__glibcxx_assert(__ret == 0);
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}
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bool
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try_lock()
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{
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int __ret = __glibcxx_rwlock_trywrlock(&_M_rwlock);
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if (__ret == EBUSY) return false;
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// Errors not handled: EINVAL
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__glibcxx_assert(__ret == 0);
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return true;
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}
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void
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unlock()
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{
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int __ret __attribute((__unused__)) = __glibcxx_rwlock_unlock(&_M_rwlock);
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// Errors not handled: EPERM, EBUSY, EINVAL
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__glibcxx_assert(__ret == 0);
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}
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// Shared ownership
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void
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lock_shared()
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{
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int __ret;
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// We retry if we exceeded the maximum number of read locks supported by
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// the POSIX implementation; this can result in busy-waiting, but this
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// is okay based on the current specification of forward progress
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// guarantees by the standard.
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do
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__ret = __glibcxx_rwlock_rdlock(&_M_rwlock);
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while (__ret == EAGAIN);
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if (__ret == EDEADLK)
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__throw_system_error(int(errc::resource_deadlock_would_occur));
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// Errors not handled: EINVAL
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__glibcxx_assert(__ret == 0);
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}
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bool
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try_lock_shared()
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{
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int __ret = __glibcxx_rwlock_tryrdlock(&_M_rwlock);
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// If the maximum number of read locks has been exceeded, we just fail
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// to acquire the lock. Unlike for lock(), we are not allowed to throw
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// an exception.
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if (__ret == EBUSY || __ret == EAGAIN) return false;
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// Errors not handled: EINVAL
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__glibcxx_assert(__ret == 0);
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return true;
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}
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void
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unlock_shared()
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{
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unlock();
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}
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void* native_handle() { return &_M_rwlock; }
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};
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#endif
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#if ! (_GLIBCXX_USE_PTHREAD_RWLOCK_T && _GTHREAD_USE_MUTEX_TIMEDLOCK)
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/// A shared mutex type implemented using std::condition_variable.
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class __shared_mutex_cv
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{
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friend class shared_timed_mutex;
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// Based on Howard Hinnant's reference implementation from N2406.
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// The high bit of _M_state is the write-entered flag which is set to
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// indicate a writer has taken the lock or is queuing to take the lock.
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// The remaining bits are the count of reader locks.
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//
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// To take a reader lock, block on gate1 while the write-entered flag is
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// set or the maximum number of reader locks is held, then increment the
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// reader lock count.
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// To release, decrement the count, then if the write-entered flag is set
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// and the count is zero then signal gate2 to wake a queued writer,
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// otherwise if the maximum number of reader locks was held signal gate1
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// to wake a reader.
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//
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// To take a writer lock, block on gate1 while the write-entered flag is
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// set, then set the write-entered flag to start queueing, then block on
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// gate2 while the number of reader locks is non-zero.
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// To release, unset the write-entered flag and signal gate1 to wake all
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// blocked readers and writers.
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//
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// This means that when no reader locks are held readers and writers get
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// equal priority. When one or more reader locks is held a writer gets
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// priority and no more reader locks can be taken while the writer is
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// queued.
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// Only locked when accessing _M_state or waiting on condition variables.
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mutex _M_mut;
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// Used to block while write-entered is set or reader count at maximum.
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condition_variable _M_gate1;
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// Used to block queued writers while reader count is non-zero.
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condition_variable _M_gate2;
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// The write-entered flag and reader count.
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unsigned _M_state;
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static constexpr unsigned _S_write_entered
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= 1U << (sizeof(unsigned)*__CHAR_BIT__ - 1);
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static constexpr unsigned _S_max_readers = ~_S_write_entered;
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// Test whether the write-entered flag is set. _M_mut must be locked.
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bool _M_write_entered() const { return _M_state & _S_write_entered; }
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// The number of reader locks currently held. _M_mut must be locked.
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unsigned _M_readers() const { return _M_state & _S_max_readers; }
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public:
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__shared_mutex_cv() : _M_state(0) {}
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~__shared_mutex_cv()
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{
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__glibcxx_assert( _M_state == 0 );
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}
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__shared_mutex_cv(const __shared_mutex_cv&) = delete;
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__shared_mutex_cv& operator=(const __shared_mutex_cv&) = delete;
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// Exclusive ownership
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void
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lock()
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{
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unique_lock<mutex> __lk(_M_mut);
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// Wait until we can set the write-entered flag.
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_M_gate1.wait(__lk, [=]{ return !_M_write_entered(); });
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_M_state |= _S_write_entered;
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// Then wait until there are no more readers.
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_M_gate2.wait(__lk, [=]{ return _M_readers() == 0; });
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}
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bool
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try_lock()
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{
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unique_lock<mutex> __lk(_M_mut, try_to_lock);
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if (__lk.owns_lock() && _M_state == 0)
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{
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_M_state = _S_write_entered;
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return true;
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}
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return false;
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}
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void
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unlock()
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{
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lock_guard<mutex> __lk(_M_mut);
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__glibcxx_assert( _M_write_entered() );
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_M_state = 0;
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// call notify_all() while mutex is held so that another thread can't
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// lock and unlock the mutex then destroy *this before we make the call.
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_M_gate1.notify_all();
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}
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// Shared ownership
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void
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lock_shared()
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{
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unique_lock<mutex> __lk(_M_mut);
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_M_gate1.wait(__lk, [=]{ return _M_state < _S_max_readers; });
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++_M_state;
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}
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bool
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try_lock_shared()
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{
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unique_lock<mutex> __lk(_M_mut, try_to_lock);
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if (!__lk.owns_lock())
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return false;
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if (_M_state < _S_max_readers)
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{
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++_M_state;
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return true;
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}
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return false;
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}
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void
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unlock_shared()
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{
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lock_guard<mutex> __lk(_M_mut);
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__glibcxx_assert( _M_readers() > 0 );
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auto __prev = _M_state--;
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if (_M_write_entered())
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{
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// Wake the queued writer if there are no more readers.
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if (_M_readers() == 0)
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_M_gate2.notify_one();
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// No need to notify gate1 because we give priority to the queued
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// writer, and that writer will eventually notify gate1 after it
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// clears the write-entered flag.
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}
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else
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{
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// Wake any thread that was blocked on reader overflow.
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if (__prev == _S_max_readers)
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_M_gate1.notify_one();
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}
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}
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};
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#endif
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/// @endcond
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#if __cplusplus >= 201703L
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/// The standard shared mutex type.
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class shared_mutex
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{
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public:
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shared_mutex() = default;
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~shared_mutex() = default;
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shared_mutex(const shared_mutex&) = delete;
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shared_mutex& operator=(const shared_mutex&) = delete;
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// Exclusive ownership
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void lock() { _M_impl.lock(); }
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bool try_lock() { return _M_impl.try_lock(); }
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void unlock() { _M_impl.unlock(); }
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// Shared ownership
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void lock_shared() { _M_impl.lock_shared(); }
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bool try_lock_shared() { return _M_impl.try_lock_shared(); }
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void unlock_shared() { _M_impl.unlock_shared(); }
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#if _GLIBCXX_USE_PTHREAD_RWLOCK_T
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typedef void* native_handle_type;
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native_handle_type native_handle() { return _M_impl.native_handle(); }
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private:
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__shared_mutex_pthread _M_impl;
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#else
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private:
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__shared_mutex_cv _M_impl;
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#endif
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};
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#endif // C++17
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/// @cond undocumented
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#if _GLIBCXX_USE_PTHREAD_RWLOCK_T && _GTHREAD_USE_MUTEX_TIMEDLOCK
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using __shared_timed_mutex_base = __shared_mutex_pthread;
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#else
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using __shared_timed_mutex_base = __shared_mutex_cv;
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#endif
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/// @endcond
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/// The standard shared timed mutex type.
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class shared_timed_mutex
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: private __shared_timed_mutex_base
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{
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using _Base = __shared_timed_mutex_base;
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// Must use the same clock as condition_variable for __shared_mutex_cv.
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#ifdef _GLIBCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK
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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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public:
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shared_timed_mutex() = default;
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~shared_timed_mutex() = default;
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shared_timed_mutex(const shared_timed_mutex&) = delete;
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shared_timed_mutex& operator=(const shared_timed_mutex&) = delete;
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// Exclusive ownership
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void lock() { _Base::lock(); }
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bool try_lock() { return _Base::try_lock(); }
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void unlock() { _Base::unlock(); }
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template<typename _Rep, typename _Period>
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bool
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try_lock_for(const chrono::duration<_Rep, _Period>& __rtime)
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{
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auto __rt = chrono::duration_cast<__clock_t::duration>(__rtime);
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if (ratio_greater<__clock_t::period, _Period>())
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++__rt;
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return try_lock_until(__clock_t::now() + __rt);
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}
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|
// Shared ownership
|
|
|
|
void lock_shared() { _Base::lock_shared(); }
|
|
bool try_lock_shared() { return _Base::try_lock_shared(); }
|
|
void unlock_shared() { _Base::unlock_shared(); }
|
|
|
|
template<typename _Rep, typename _Period>
|
|
bool
|
|
try_lock_shared_for(const chrono::duration<_Rep, _Period>& __rtime)
|
|
{
|
|
auto __rt = chrono::duration_cast<__clock_t::duration>(__rtime);
|
|
if (ratio_greater<__clock_t::period, _Period>())
|
|
++__rt;
|
|
return try_lock_shared_until(__clock_t::now() + __rt);
|
|
}
|
|
|
|
#if _GLIBCXX_USE_PTHREAD_RWLOCK_T && _GTHREAD_USE_MUTEX_TIMEDLOCK
|
|
|
|
// Exclusive ownership
|
|
|
|
template<typename _Duration>
|
|
bool
|
|
try_lock_until(const chrono::time_point<chrono::system_clock,
|
|
_Duration>& __atime)
|
|
{
|
|
auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
|
|
auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
|
|
|
|
__gthread_time_t __ts =
|
|
{
|
|
static_cast<std::time_t>(__s.time_since_epoch().count()),
|
|
static_cast<long>(__ns.count())
|
|
};
|
|
|
|
int __ret = __glibcxx_rwlock_timedwrlock(&_M_rwlock, &__ts);
|
|
// On self-deadlock, we just fail to acquire the lock. Technically,
|
|
// the program violated the precondition.
|
|
if (__ret == ETIMEDOUT || __ret == EDEADLK)
|
|
return false;
|
|
// Errors not handled: EINVAL
|
|
__glibcxx_assert(__ret == 0);
|
|
return true;
|
|
}
|
|
|
|
#ifdef _GLIBCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK
|
|
template<typename _Duration>
|
|
bool
|
|
try_lock_until(const chrono::time_point<chrono::steady_clock,
|
|
_Duration>& __atime)
|
|
{
|
|
auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
|
|
auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
|
|
|
|
__gthread_time_t __ts =
|
|
{
|
|
static_cast<std::time_t>(__s.time_since_epoch().count()),
|
|
static_cast<long>(__ns.count())
|
|
};
|
|
|
|
int __ret = pthread_rwlock_clockwrlock(&_M_rwlock, CLOCK_MONOTONIC,
|
|
&__ts);
|
|
// On self-deadlock, we just fail to acquire the lock. Technically,
|
|
// the program violated the precondition.
|
|
if (__ret == ETIMEDOUT || __ret == EDEADLK)
|
|
return false;
|
|
// Errors not handled: EINVAL
|
|
__glibcxx_assert(__ret == 0);
|
|
return true;
|
|
}
|
|
#endif
|
|
|
|
template<typename _Clock, typename _Duration>
|
|
bool
|
|
try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime)
|
|
{
|
|
#if __cplusplus > 201703L
|
|
static_assert(chrono::is_clock_v<_Clock>);
|
|
#endif
|
|
// The user-supplied clock may not tick at the same rate as
|
|
// steady_clock, so we must loop in order to guarantee that
|
|
// the timeout has expired before returning false.
|
|
typename _Clock::time_point __now = _Clock::now();
|
|
do {
|
|
auto __rtime = __atime - __now;
|
|
if (try_lock_for(__rtime))
|
|
return true;
|
|
__now = _Clock::now();
|
|
} while (__atime > __now);
|
|
return false;
|
|
}
|
|
|
|
// Shared ownership
|
|
|
|
template<typename _Duration>
|
|
bool
|
|
try_lock_shared_until(const chrono::time_point<chrono::system_clock,
|
|
_Duration>& __atime)
|
|
{
|
|
auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
|
|
auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
|
|
|
|
__gthread_time_t __ts =
|
|
{
|
|
static_cast<std::time_t>(__s.time_since_epoch().count()),
|
|
static_cast<long>(__ns.count())
|
|
};
|
|
|
|
int __ret;
|
|
// Unlike for lock(), we are not allowed to throw an exception so if
|
|
// the maximum number of read locks has been exceeded, or we would
|
|
// deadlock, we just try to acquire the lock again (and will time out
|
|
// eventually).
|
|
// In cases where we would exceed the maximum number of read locks
|
|
// throughout the whole time until the timeout, we will fail to
|
|
// acquire the lock even if it would be logically free; however, this
|
|
// is allowed by the standard, and we made a "strong effort"
|
|
// (see C++14 30.4.1.4p26).
|
|
// For cases where the implementation detects a deadlock we
|
|
// intentionally block and timeout so that an early return isn't
|
|
// mistaken for a spurious failure, which might help users realise
|
|
// there is a deadlock.
|
|
do
|
|
__ret = __glibcxx_rwlock_timedrdlock(&_M_rwlock, &__ts);
|
|
while (__ret == EAGAIN || __ret == EDEADLK);
|
|
if (__ret == ETIMEDOUT)
|
|
return false;
|
|
// Errors not handled: EINVAL
|
|
__glibcxx_assert(__ret == 0);
|
|
return true;
|
|
}
|
|
|
|
#ifdef _GLIBCXX_USE_PTHREAD_RWLOCK_CLOCKLOCK
|
|
template<typename _Duration>
|
|
bool
|
|
try_lock_shared_until(const chrono::time_point<chrono::steady_clock,
|
|
_Duration>& __atime)
|
|
{
|
|
auto __s = chrono::time_point_cast<chrono::seconds>(__atime);
|
|
auto __ns = chrono::duration_cast<chrono::nanoseconds>(__atime - __s);
|
|
|
|
__gthread_time_t __ts =
|
|
{
|
|
static_cast<std::time_t>(__s.time_since_epoch().count()),
|
|
static_cast<long>(__ns.count())
|
|
};
|
|
|
|
int __ret = pthread_rwlock_clockrdlock(&_M_rwlock, CLOCK_MONOTONIC,
|
|
&__ts);
|
|
// On self-deadlock, we just fail to acquire the lock. Technically,
|
|
// the program violated the precondition.
|
|
if (__ret == ETIMEDOUT || __ret == EDEADLK)
|
|
return false;
|
|
// Errors not handled: EINVAL
|
|
__glibcxx_assert(__ret == 0);
|
|
return true;
|
|
}
|
|
#endif
|
|
|
|
template<typename _Clock, typename _Duration>
|
|
bool
|
|
try_lock_shared_until(const chrono::time_point<_Clock,
|
|
_Duration>& __atime)
|
|
{
|
|
#if __cplusplus > 201703L
|
|
static_assert(chrono::is_clock_v<_Clock>);
|
|
#endif
|
|
// The user-supplied clock may not tick at the same rate as
|
|
// steady_clock, so we must loop in order to guarantee that
|
|
// the timeout has expired before returning false.
|
|
typename _Clock::time_point __now = _Clock::now();
|
|
do {
|
|
auto __rtime = __atime - __now;
|
|
if (try_lock_shared_for(__rtime))
|
|
return true;
|
|
__now = _Clock::now();
|
|
} while (__atime > __now);
|
|
return false;
|
|
}
|
|
|
|
#else // ! (_GLIBCXX_USE_PTHREAD_RWLOCK_T && _GTHREAD_USE_MUTEX_TIMEDLOCK)
|
|
|
|
// Exclusive ownership
|
|
|
|
template<typename _Clock, typename _Duration>
|
|
bool
|
|
try_lock_until(const chrono::time_point<_Clock, _Duration>& __abs_time)
|
|
{
|
|
unique_lock<mutex> __lk(_M_mut);
|
|
if (!_M_gate1.wait_until(__lk, __abs_time,
|
|
[=]{ return !_M_write_entered(); }))
|
|
{
|
|
return false;
|
|
}
|
|
_M_state |= _S_write_entered;
|
|
if (!_M_gate2.wait_until(__lk, __abs_time,
|
|
[=]{ return _M_readers() == 0; }))
|
|
{
|
|
_M_state ^= _S_write_entered;
|
|
// Wake all threads blocked while the write-entered flag was set.
|
|
_M_gate1.notify_all();
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
// Shared ownership
|
|
|
|
template <typename _Clock, typename _Duration>
|
|
bool
|
|
try_lock_shared_until(const chrono::time_point<_Clock,
|
|
_Duration>& __abs_time)
|
|
{
|
|
unique_lock<mutex> __lk(_M_mut);
|
|
if (!_M_gate1.wait_until(__lk, __abs_time,
|
|
[=]{ return _M_state < _S_max_readers; }))
|
|
{
|
|
return false;
|
|
}
|
|
++_M_state;
|
|
return true;
|
|
}
|
|
|
|
#endif // _GLIBCXX_USE_PTHREAD_RWLOCK_T && _GTHREAD_USE_MUTEX_TIMEDLOCK
|
|
};
|
|
#endif // _GLIBCXX_HAS_GTHREADS
|
|
|
|
/// shared_lock
|
|
template<typename _Mutex>
|
|
class shared_lock
|
|
{
|
|
public:
|
|
typedef _Mutex mutex_type;
|
|
|
|
// Shared locking
|
|
|
|
shared_lock() noexcept : _M_pm(nullptr), _M_owns(false) { }
|
|
|
|
explicit
|
|
shared_lock(mutex_type& __m)
|
|
: _M_pm(std::__addressof(__m)), _M_owns(true)
|
|
{ __m.lock_shared(); }
|
|
|
|
shared_lock(mutex_type& __m, defer_lock_t) noexcept
|
|
: _M_pm(std::__addressof(__m)), _M_owns(false) { }
|
|
|
|
shared_lock(mutex_type& __m, try_to_lock_t)
|
|
: _M_pm(std::__addressof(__m)), _M_owns(__m.try_lock_shared()) { }
|
|
|
|
shared_lock(mutex_type& __m, adopt_lock_t)
|
|
: _M_pm(std::__addressof(__m)), _M_owns(true) { }
|
|
|
|
template<typename _Clock, typename _Duration>
|
|
shared_lock(mutex_type& __m,
|
|
const chrono::time_point<_Clock, _Duration>& __abs_time)
|
|
: _M_pm(std::__addressof(__m)),
|
|
_M_owns(__m.try_lock_shared_until(__abs_time)) { }
|
|
|
|
template<typename _Rep, typename _Period>
|
|
shared_lock(mutex_type& __m,
|
|
const chrono::duration<_Rep, _Period>& __rel_time)
|
|
: _M_pm(std::__addressof(__m)),
|
|
_M_owns(__m.try_lock_shared_for(__rel_time)) { }
|
|
|
|
~shared_lock()
|
|
{
|
|
if (_M_owns)
|
|
_M_pm->unlock_shared();
|
|
}
|
|
|
|
shared_lock(shared_lock const&) = delete;
|
|
shared_lock& operator=(shared_lock const&) = delete;
|
|
|
|
shared_lock(shared_lock&& __sl) noexcept : shared_lock()
|
|
{ swap(__sl); }
|
|
|
|
shared_lock&
|
|
operator=(shared_lock&& __sl) noexcept
|
|
{
|
|
shared_lock(std::move(__sl)).swap(*this);
|
|
return *this;
|
|
}
|
|
|
|
void
|
|
lock()
|
|
{
|
|
_M_lockable();
|
|
_M_pm->lock_shared();
|
|
_M_owns = true;
|
|
}
|
|
|
|
bool
|
|
try_lock()
|
|
{
|
|
_M_lockable();
|
|
return _M_owns = _M_pm->try_lock_shared();
|
|
}
|
|
|
|
template<typename _Rep, typename _Period>
|
|
bool
|
|
try_lock_for(const chrono::duration<_Rep, _Period>& __rel_time)
|
|
{
|
|
_M_lockable();
|
|
return _M_owns = _M_pm->try_lock_shared_for(__rel_time);
|
|
}
|
|
|
|
template<typename _Clock, typename _Duration>
|
|
bool
|
|
try_lock_until(const chrono::time_point<_Clock, _Duration>& __abs_time)
|
|
{
|
|
_M_lockable();
|
|
return _M_owns = _M_pm->try_lock_shared_until(__abs_time);
|
|
}
|
|
|
|
void
|
|
unlock()
|
|
{
|
|
if (!_M_owns)
|
|
__throw_system_error(int(errc::resource_deadlock_would_occur));
|
|
_M_pm->unlock_shared();
|
|
_M_owns = false;
|
|
}
|
|
|
|
// Setters
|
|
|
|
void
|
|
swap(shared_lock& __u) noexcept
|
|
{
|
|
std::swap(_M_pm, __u._M_pm);
|
|
std::swap(_M_owns, __u._M_owns);
|
|
}
|
|
|
|
mutex_type*
|
|
release() noexcept
|
|
{
|
|
_M_owns = false;
|
|
return std::__exchange(_M_pm, nullptr);
|
|
}
|
|
|
|
// Getters
|
|
|
|
bool owns_lock() const noexcept { return _M_owns; }
|
|
|
|
explicit operator bool() const noexcept { return _M_owns; }
|
|
|
|
mutex_type* mutex() const noexcept { return _M_pm; }
|
|
|
|
private:
|
|
void
|
|
_M_lockable() const
|
|
{
|
|
if (_M_pm == nullptr)
|
|
__throw_system_error(int(errc::operation_not_permitted));
|
|
if (_M_owns)
|
|
__throw_system_error(int(errc::resource_deadlock_would_occur));
|
|
}
|
|
|
|
mutex_type* _M_pm;
|
|
bool _M_owns;
|
|
};
|
|
|
|
/// Swap specialization for shared_lock
|
|
/// @relates shared_mutex
|
|
template<typename _Mutex>
|
|
void
|
|
swap(shared_lock<_Mutex>& __x, shared_lock<_Mutex>& __y) noexcept
|
|
{ __x.swap(__y); }
|
|
|
|
// @} group mutexes
|
|
_GLIBCXX_END_NAMESPACE_VERSION
|
|
} // namespace
|
|
|
|
#endif // C++14
|
|
|
|
#endif // _GLIBCXX_SHARED_MUTEX
|