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 38 namespace __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
