1 // Support for atomic operations -*- C++ -*- 2 3 // Copyright (C) 2004, 2005, 2006, 2008, 2009, 2010, 2011, 2012 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 37 namespace __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 46 static inline _Atomic_word 47 __exchange_and_add(volatile _Atomic_word* __mem, int __val) 48 { return __atomic_fetch_add(__mem, __val, __ATOMIC_ACQ_REL); } 49 50 static inline void 51 __atomic_add(volatile _Atomic_word* __mem, int __val) 52 { __atomic_fetch_add(__mem, __val, __ATOMIC_ACQ_REL); } 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
