1// Support for atomic operations -*- C++ -*- 2 3// Copyright (C) 2004, 2005, 2006 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 2, 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// You should have received a copy of the GNU General Public License along 17// with this library; see the file COPYING. If not, write to the Free 18// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, 19// USA. 20 21// As a special exception, you may use this file as part of a free software 22// library without restriction. Specifically, if other files instantiate 23// templates or use macros or inline functions from this file, or you compile 24// this file and link it with other files to produce an executable, this 25// file does not by itself cause the resulting executable to be covered by 26// the GNU General Public License. This exception does not however 27// invalidate any other reasons why the executable file might be covered by 28// the GNU General Public License. 29 30/** @file atomicity.h 31 * This is an internal header file, included by other library headers. 32 * You should not attempt to use it directly. 33 */ 34 35#ifndef _GLIBCXX_ATOMICITY_H 36#define _GLIBCXX_ATOMICITY_H 1 37 38#include <bits/c++config.h> 39#include <bits/gthr.h> 40#include <bits/atomic_word.h> 41 42_GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx) 43 44 // Functions for portable atomic access. 45 // To abstract locking primitives across all thread policies, use: 46 // __exchange_and_add_dispatch 47 // __atomic_add_dispatch 48#ifdef _GLIBCXX_ATOMIC_BUILTINS 49 static inline _Atomic_word 50 __exchange_and_add(volatile _Atomic_word* __mem, int __val) 51 { return __sync_fetch_and_add(__mem, __val); } 52 53 static inline void 54 __atomic_add(volatile _Atomic_word* __mem, int __val) 55 { __sync_fetch_and_add(__mem, __val); } 56#else 57 _Atomic_word 58 __attribute__ ((__unused__)) 59 __exchange_and_add(volatile _Atomic_word*, int); 60 61 void 62 __attribute__ ((__unused__)) 63 __atomic_add(volatile _Atomic_word*, int); 64#endif 65 66 static inline _Atomic_word 67 __exchange_and_add_single(_Atomic_word* __mem, int __val) 68 { 69 _Atomic_word __result = *__mem; 70 *__mem += __val; 71 return __result; 72 } 73 74 static inline void 75 __atomic_add_single(_Atomic_word* __mem, int __val) 76 { *__mem += __val; } 77 78 static inline _Atomic_word 79 __attribute__ ((__unused__)) 80 __exchange_and_add_dispatch(_Atomic_word* __mem, int __val) 81 { 82#ifdef __GTHREADS 83 if (__gthread_active_p()) 84 return __exchange_and_add(__mem, __val); 85 else 86 return __exchange_and_add_single(__mem, __val); 87#else 88 return __exchange_and_add_single(__mem, __val); 89#endif 90 } 91 92 static inline void 93 __attribute__ ((__unused__)) 94 __atomic_add_dispatch(_Atomic_word* __mem, int __val) 95 { 96#ifdef __GTHREADS 97 if (__gthread_active_p()) 98 __atomic_add(__mem, __val); 99 else 100 __atomic_add_single(__mem, __val); 101#else 102 __atomic_add_single(__mem, __val); 103#endif 104 } 105 106_GLIBCXX_END_NAMESPACE 107 108// Even if the CPU doesn't need a memory barrier, we need to ensure 109// that the compiler doesn't reorder memory accesses across the 110// barriers. 111#ifndef _GLIBCXX_READ_MEM_BARRIER 112#define _GLIBCXX_READ_MEM_BARRIER __asm __volatile ("":::"memory") 113#endif 114#ifndef _GLIBCXX_WRITE_MEM_BARRIER 115#define _GLIBCXX_WRITE_MEM_BARRIER __asm __volatile ("":::"memory") 116#endif 117 118#endif 119