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