/*
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* Distributed under the Boost Software License, Version 1.0.
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* (See accompanying file LICENSE_1_0.txt or copy at
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* http://www.boost.org/LICENSE_1_0.txt)
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*
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* Copyright (c) 2020 Andrey Semashev
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*/
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/*!
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* \file atomic/detail/futex.hpp
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*
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* This header defines wrappers around futex syscall.
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*
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* http://man7.org/linux/man-pages/man2/futex.2.html
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* https://man.openbsd.org/futex
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*/
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#ifndef BOOST_ATOMIC_DETAIL_FUTEX_HPP_INCLUDED_
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#define BOOST_ATOMIC_DETAIL_FUTEX_HPP_INCLUDED_
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#include <boost/atomic/detail/config.hpp>
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#ifdef BOOST_HAS_PRAGMA_ONCE
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#pragma once
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#endif
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#if defined(__linux__) || defined(__OpenBSD__) || defined(__NETBSD__) || defined(__NetBSD__)
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#include <sys/syscall.h>
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// Some Android NDKs (Google NDK and older Crystax.NET NDK versions) don't define SYS_futex.
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#if defined(SYS_futex)
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#define BOOST_ATOMIC_DETAIL_SYS_FUTEX SYS_futex
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#elif defined(__NR_futex)
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#define BOOST_ATOMIC_DETAIL_SYS_FUTEX __NR_futex
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#elif defined(SYS___futex)
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// NetBSD defines SYS___futex, which has slightly different parameters. Basically, it has decoupled timeout and val2 parameters:
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// int __futex(int *addr1, int op, int val1, const struct timespec *timeout, int *addr2, int val2, int val3);
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// https://ftp.netbsd.org/pub/NetBSD/NetBSD-current/src/sys/sys/syscall.h
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// http://bxr.su/NetBSD/sys/kern/sys_futex.c
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#define BOOST_ATOMIC_DETAIL_SYS_FUTEX SYS___futex
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#define BOOST_ATOMIC_DETAIL_NETBSD_FUTEX
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#endif
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#if defined(BOOST_ATOMIC_DETAIL_SYS_FUTEX)
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#include <cstddef>
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#if defined(__linux__)
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#include <linux/futex.h>
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#else
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#include <sys/futex.h>
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#endif
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#include <boost/atomic/detail/intptr.hpp>
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#include <boost/atomic/detail/header.hpp>
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#define BOOST_ATOMIC_DETAIL_HAS_FUTEX
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#if defined(FUTEX_PRIVATE_FLAG)
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#define BOOST_ATOMIC_DETAIL_FUTEX_PRIVATE_FLAG FUTEX_PRIVATE_FLAG
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#else
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#define BOOST_ATOMIC_DETAIL_FUTEX_PRIVATE_FLAG 0
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#endif
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namespace boost {
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namespace atomics {
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namespace detail {
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//! Invokes an operation on the futex
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BOOST_FORCEINLINE int futex_invoke(void* addr1, int op, unsigned int val1, const void* timeout = NULL, void* addr2 = NULL, unsigned int val3 = 0) BOOST_NOEXCEPT
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{
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#if !defined(BOOST_ATOMIC_DETAIL_NETBSD_FUTEX)
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return ::syscall(BOOST_ATOMIC_DETAIL_SYS_FUTEX, addr1, op, val1, timeout, addr2, val3);
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#else
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// Pass 0 in val2.
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return ::syscall(BOOST_ATOMIC_DETAIL_SYS_FUTEX, addr1, op, val1, timeout, addr2, 0u, val3);
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#endif
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}
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//! Invokes an operation on the futex
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BOOST_FORCEINLINE int futex_invoke(void* addr1, int op, unsigned int val1, unsigned int val2, void* addr2 = NULL, unsigned int val3 = 0) BOOST_NOEXCEPT
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{
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#if !defined(BOOST_ATOMIC_DETAIL_NETBSD_FUTEX)
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return ::syscall(BOOST_ATOMIC_DETAIL_SYS_FUTEX, addr1, op, val1, static_cast< atomics::detail::uintptr_t >(val2), addr2, val3);
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#else
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// Pass NULL in timeout.
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return ::syscall(BOOST_ATOMIC_DETAIL_SYS_FUTEX, addr1, op, val1, static_cast< void* >(NULL), addr2, val2, val3);
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#endif
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}
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//! Checks that the value \c pval is \c expected and blocks
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BOOST_FORCEINLINE int futex_wait(void* pval, unsigned int expected) BOOST_NOEXCEPT
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{
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return futex_invoke(pval, FUTEX_WAIT, expected);
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}
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//! Checks that the value \c pval is \c expected and blocks
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BOOST_FORCEINLINE int futex_wait_private(void* pval, unsigned int expected) BOOST_NOEXCEPT
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{
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return futex_invoke(pval, FUTEX_WAIT | BOOST_ATOMIC_DETAIL_FUTEX_PRIVATE_FLAG, expected);
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}
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//! Wakes the specified number of threads waiting on the futex
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BOOST_FORCEINLINE int futex_signal(void* pval, unsigned int count = 1u) BOOST_NOEXCEPT
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{
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return futex_invoke(pval, FUTEX_WAKE, count);
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}
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//! Wakes the specified number of threads waiting on the futex
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BOOST_FORCEINLINE int futex_signal_private(void* pval, unsigned int count = 1u) BOOST_NOEXCEPT
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{
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return futex_invoke(pval, FUTEX_WAKE | BOOST_ATOMIC_DETAIL_FUTEX_PRIVATE_FLAG, count);
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}
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//! Wakes all threads waiting on the futex
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BOOST_FORCEINLINE int futex_broadcast(void* pval) BOOST_NOEXCEPT
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{
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return futex_signal(pval, (~static_cast< unsigned int >(0u)) >> 1);
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}
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//! Wakes all threads waiting on the futex
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BOOST_FORCEINLINE int futex_broadcast_private(void* pval) BOOST_NOEXCEPT
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{
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return futex_signal_private(pval, (~static_cast< unsigned int >(0u)) >> 1);
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}
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//! Wakes the wake_count threads waiting on the futex pval1 and requeues up to requeue_count of the blocked threads onto another futex pval2
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BOOST_FORCEINLINE int futex_requeue(void* pval1, void* pval2, unsigned int wake_count = 1u, unsigned int requeue_count = (~static_cast< unsigned int >(0u)) >> 1) BOOST_NOEXCEPT
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{
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return futex_invoke(pval1, FUTEX_REQUEUE, wake_count, requeue_count, pval2);
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}
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//! Wakes the wake_count threads waiting on the futex pval1 and requeues up to requeue_count of the blocked threads onto another futex pval2
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BOOST_FORCEINLINE int futex_requeue_private(void* pval1, void* pval2, unsigned int wake_count = 1u, unsigned int requeue_count = (~static_cast< unsigned int >(0u)) >> 1) BOOST_NOEXCEPT
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{
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return futex_invoke(pval1, FUTEX_REQUEUE | BOOST_ATOMIC_DETAIL_FUTEX_PRIVATE_FLAG, wake_count, requeue_count, pval2);
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}
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} // namespace detail
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} // namespace atomics
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} // namespace boost
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#include <boost/atomic/detail/footer.hpp>
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#endif // defined(BOOST_ATOMIC_DETAIL_SYS_FUTEX)
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#endif // defined(__linux__) || defined(__OpenBSD__) || defined(__NETBSD__) || defined(__NetBSD__)
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#endif // BOOST_ATOMIC_DETAIL_FUTEX_HPP_INCLUDED_
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