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편집 파일: atomicity.h

// Support for atomic operations -*- C++ -*- // Copyright (C) 2004-2021 Free Software Foundation, Inc. // // This file is part of the GNU ISO C++ Library. This library is free // software; you can redistribute it and/or modify it under the // terms of the GNU General Public License as published by the // Free Software Foundation; either version 3, or (at your option) // any later version. // This library is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // Under Section 7 of GPL version 3, you are granted additional // permissions described in the GCC Runtime Library Exception, version // 3.1, as published by the Free Software Foundation. // You should have received a copy of the GNU General Public License and // a copy of the GCC Runtime Library Exception along with this program; // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see // <http://www.gnu.org/licenses/>. /** @file ext/atomicity.h * This file is a GNU extension to the Standard C++ Library. */ #ifndef _GLIBCXX_ATOMICITY_H #define _GLIBCXX_ATOMICITY_H 1 #pragma GCC system_header #include <bits/c++config.h> #include <bits/gthr.h> #include <bits/atomic_word.h> #if __has_include(<sys/single_threaded.h>) # include <sys/single_threaded.h> #endif namespace __gnu_cxx _GLIBCXX_VISIBILITY(default) { _GLIBCXX_BEGIN_NAMESPACE_VERSION __attribute__((__always_inline__)) inline bool __is_single_threaded() _GLIBCXX_NOTHROW { #ifndef __GTHREADS return true; #elif __has_include(<sys/single_threaded.h>) return ::__libc_single_threaded; #else return !__gthread_active_p(); #endif } // Functions for portable atomic access. // To abstract locking primitives across all thread policies, use: // __exchange_and_add_dispatch // __atomic_add_dispatch #ifdef _GLIBCXX_ATOMIC_BUILTINS inline _Atomic_word __attribute__((__always_inline__)) __exchange_and_add(volatile _Atomic_word* __mem, int __val) { return __atomic_fetch_add(__mem, __val, __ATOMIC_ACQ_REL); } inline void __attribute__((__always_inline__)) __atomic_add(volatile _Atomic_word* __mem, int __val) { __atomic_fetch_add(__mem, __val, __ATOMIC_ACQ_REL); } #else _Atomic_word __exchange_and_add(volatile _Atomic_word*, int) _GLIBCXX_NOTHROW; void __atomic_add(volatile _Atomic_word*, int) _GLIBCXX_NOTHROW; #endif inline _Atomic_word __attribute__((__always_inline__)) __exchange_and_add_single(_Atomic_word* __mem, int __val) { _Atomic_word __result = *__mem; *__mem += __val; return __result; } inline void __attribute__((__always_inline__)) __atomic_add_single(_Atomic_word* __mem, int __val) { *__mem += __val; } inline _Atomic_word __attribute__ ((__always_inline__)) __exchange_and_add_dispatch(_Atomic_word* __mem, int __val) { if (__is_single_threaded()) return __exchange_and_add_single(__mem, __val); else return __exchange_and_add(__mem, __val); } inline void __attribute__ ((__always_inline__)) __atomic_add_dispatch(_Atomic_word* __mem, int __val) { if (__is_single_threaded()) __atomic_add_single(__mem, __val); else __atomic_add(__mem, __val); } _GLIBCXX_END_NAMESPACE_VERSION } // namespace // Even if the CPU doesn't need a memory barrier, we need to ensure // that the compiler doesn't reorder memory accesses across the // barriers. #ifndef _GLIBCXX_READ_MEM_BARRIER #define _GLIBCXX_READ_MEM_BARRIER __atomic_thread_fence (__ATOMIC_ACQUIRE) #endif #ifndef _GLIBCXX_WRITE_MEM_BARRIER #define _GLIBCXX_WRITE_MEM_BARRIER __atomic_thread_fence (__ATOMIC_RELEASE) #endif #endif