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 primatives 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