1// Support for atomic operations -*- C++ -*- 2 3// Copyright (C) 2004-2013 Free Software Foundation, Inc. 4// 5// This file is part of the GNU ISO C++ Library. This library is free 6// software; you can redistribute it and/or modify it under the 7// terms of the GNU General Public License as published by the 8// Free Software Foundation; either version 3, or (at your option) 9// any later version. 10 11// This library is distributed in the hope that it will be useful, 12// but WITHOUT ANY WARRANTY; without even the implied warranty of 13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14// GNU General Public License for more details. 15 16// Under Section 7 of GPL version 3, you are granted additional 17// permissions described in the GCC Runtime Library Exception, version 18// 3.1, as published by the Free Software Foundation. 19 20// You should have received a copy of the GNU General Public License and 21// a copy of the GCC Runtime Library Exception along with this program; 22// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 23// <http://www.gnu.org/licenses/>. 24 25/** @file ext/atomicity.h 26 * This file is a GNU extension to the Standard C++ Library. 27 */ 28 29#ifndef _GLIBCXX_ATOMICITY_H 30#define _GLIBCXX_ATOMICITY_H 1 31 32#pragma GCC system_header 33 34#include <bits/c++config.h> 35#include <bits/gthr.h> 36#include <bits/atomic_word.h> 37 38namespace __gnu_cxx _GLIBCXX_VISIBILITY(default) 39{ 40_GLIBCXX_BEGIN_NAMESPACE_VERSION 41 42 // Functions for portable atomic access. 43 // To abstract locking primitives across all thread policies, use: 44 // __exchange_and_add_dispatch 45 // __atomic_add_dispatch 46#ifdef _GLIBCXX_ATOMIC_BUILTINS 47 static inline _Atomic_word 48 __exchange_and_add(volatile _Atomic_word* __mem, int __val) 49 { return __atomic_fetch_add(__mem, __val, __ATOMIC_ACQ_REL); } 50 51 static inline void 52 __atomic_add(volatile _Atomic_word* __mem, int __val) 53 { __atomic_fetch_add(__mem, __val, __ATOMIC_ACQ_REL); } 54#else 55 _Atomic_word 56 __attribute__ ((__unused__)) 57 __exchange_and_add(volatile _Atomic_word*, int) throw (); 58 59 void 60 __attribute__ ((__unused__)) 61 __atomic_add(volatile _Atomic_word*, int) throw (); 62#endif 63 64 static inline _Atomic_word 65 __exchange_and_add_single(_Atomic_word* __mem, int __val) 66 { 67 _Atomic_word __result = *__mem; 68 *__mem += __val; 69 return __result; 70 } 71 72 static inline void 73 __atomic_add_single(_Atomic_word* __mem, int __val) 74 { *__mem += __val; } 75 76 static inline _Atomic_word 77 __attribute__ ((__unused__)) 78 __exchange_and_add_dispatch(_Atomic_word* __mem, int __val) 79 { 80#ifdef __GTHREADS 81 if (__gthread_active_p()) 82 return __exchange_and_add(__mem, __val); 83 else 84 return __exchange_and_add_single(__mem, __val); 85#else 86 return __exchange_and_add_single(__mem, __val); 87#endif 88 } 89 90 static inline void 91 __attribute__ ((__unused__)) 92 __atomic_add_dispatch(_Atomic_word* __mem, int __val) 93 { 94#ifdef __GTHREADS 95 if (__gthread_active_p()) 96 __atomic_add(__mem, __val); 97 else 98 __atomic_add_single(__mem, __val); 99#else 100 __atomic_add_single(__mem, __val); 101#endif 102 } 103 104_GLIBCXX_END_NAMESPACE_VERSION 105} // namespace 106 107// Even if the CPU doesn't need a memory barrier, we need to ensure 108// that the compiler doesn't reorder memory accesses across the 109// barriers. 110#ifndef _GLIBCXX_READ_MEM_BARRIER 111#define _GLIBCXX_READ_MEM_BARRIER __asm __volatile ("":::"memory") 112#endif 113#ifndef _GLIBCXX_WRITE_MEM_BARRIER 114#define _GLIBCXX_WRITE_MEM_BARRIER __asm __volatile ("":::"memory") 115#endif 116 117#endif 118