1// Support for atomic operations -*- C++ -*- 2 3// Copyright (C) 2004, 2005, 2006, 2008, 2009, 2010 4// Free Software Foundation, Inc. 5// 6// This file is part of the GNU ISO C++ Library. This library is free 7// software; you can redistribute it and/or modify it under the 8// terms of the GNU General Public License as published by the 9// Free Software Foundation; either version 3, or (at your option) 10// any later version. 11 12// This library is distributed in the hope that it will be useful, 13// but WITHOUT ANY WARRANTY; without even the implied warranty of 14// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15// GNU General Public License for more details. 16 17// Under Section 7 of GPL version 3, you are granted additional 18// permissions described in the GCC Runtime Library Exception, version 19// 3.1, as published by the Free Software Foundation. 20 21// You should have received a copy of the GNU General Public License and 22// a copy of the GCC Runtime Library Exception along with this program; 23// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 24// <http://www.gnu.org/licenses/>. 25 26/** @file ext/atomicity.h 27 * This file is a GNU extension to the Standard C++ Library. 28 */ 29 30#ifndef _GLIBCXX_ATOMICITY_H 31#define _GLIBCXX_ATOMICITY_H 1 32 33#include <bits/c++config.h> 34#include <bits/gthr.h> 35#include <bits/atomic_word.h> 36 37namespace __gnu_cxx _GLIBCXX_VISIBILITY(default) 38{ 39_GLIBCXX_BEGIN_NAMESPACE_VERSION 40 41 // Functions for portable atomic access. 42 // To abstract locking primitives across all thread policies, use: 43 // __exchange_and_add_dispatch 44 // __atomic_add_dispatch 45#ifdef _GLIBCXX_ATOMIC_BUILTINS_4 46 static inline _Atomic_word 47 __exchange_and_add(volatile _Atomic_word* __mem, int __val) 48 { return __sync_fetch_and_add(__mem, __val); } 49 50 static inline void 51 __atomic_add(volatile _Atomic_word* __mem, int __val) 52 { __sync_fetch_and_add(__mem, __val); } 53#else 54 _Atomic_word 55 __attribute__ ((__unused__)) 56 __exchange_and_add(volatile _Atomic_word*, int) throw (); 57 58 void 59 __attribute__ ((__unused__)) 60 __atomic_add(volatile _Atomic_word*, int) throw (); 61#endif 62 63 static inline _Atomic_word 64 __exchange_and_add_single(_Atomic_word* __mem, int __val) 65 { 66 _Atomic_word __result = *__mem; 67 *__mem += __val; 68 return __result; 69 } 70 71 static inline void 72 __atomic_add_single(_Atomic_word* __mem, int __val) 73 { *__mem += __val; } 74 75 static inline _Atomic_word 76 __attribute__ ((__unused__)) 77 __exchange_and_add_dispatch(_Atomic_word* __mem, int __val) 78 { 79#ifdef __GTHREADS 80 if (__gthread_active_p()) 81 return __exchange_and_add(__mem, __val); 82 else 83 return __exchange_and_add_single(__mem, __val); 84#else 85 return __exchange_and_add_single(__mem, __val); 86#endif 87 } 88 89 static inline void 90 __attribute__ ((__unused__)) 91 __atomic_add_dispatch(_Atomic_word* __mem, int __val) 92 { 93#ifdef __GTHREADS 94 if (__gthread_active_p()) 95 __atomic_add(__mem, __val); 96 else 97 __atomic_add_single(__mem, __val); 98#else 99 __atomic_add_single(__mem, __val); 100#endif 101 } 102 103_GLIBCXX_END_NAMESPACE_VERSION 104} // namespace 105 106// Even if the CPU doesn't need a memory barrier, we need to ensure 107// that the compiler doesn't reorder memory accesses across the 108// barriers. 109#ifndef _GLIBCXX_READ_MEM_BARRIER 110#define _GLIBCXX_READ_MEM_BARRIER __asm __volatile ("":::"memory") 111#endif 112#ifndef _GLIBCXX_WRITE_MEM_BARRIER 113#define _GLIBCXX_WRITE_MEM_BARRIER __asm __volatile ("":::"memory") 114#endif 115 116#endif 117