libstdc++
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00001 // Support for atomic operations -*- C++ -*- 00002 00003 // Copyright (C) 2004-2013 Free Software Foundation, Inc. 00004 // 00005 // This file is part of the GNU ISO C++ Library. This library is free 00006 // software; you can redistribute it and/or modify it under the 00007 // terms of the GNU General Public License as published by the 00008 // Free Software Foundation; either version 3, or (at your option) 00009 // any later version. 00010 00011 // This library is distributed in the hope that it will be useful, 00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of 00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00014 // GNU General Public License for more details. 00015 00016 // Under Section 7 of GPL version 3, you are granted additional 00017 // permissions described in the GCC Runtime Library Exception, version 00018 // 3.1, as published by the Free Software Foundation. 00019 00020 // You should have received a copy of the GNU General Public License and 00021 // a copy of the GCC Runtime Library Exception along with this program; 00022 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 00023 // <http://www.gnu.org/licenses/>. 00024 00025 /** @file ext/atomicity.h 00026 * This file is a GNU extension to the Standard C++ Library. 00027 */ 00028 00029 #ifndef _GLIBCXX_ATOMICITY_H 00030 #define _GLIBCXX_ATOMICITY_H 1 00031 00032 #include <bits/c++config.h> 00033 #include <bits/gthr.h> 00034 #include <bits/atomic_word.h> 00035 00036 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default) 00037 { 00038 _GLIBCXX_BEGIN_NAMESPACE_VERSION 00039 00040 // Functions for portable atomic access. 00041 // To abstract locking primitives across all thread policies, use: 00042 // __exchange_and_add_dispatch 00043 // __atomic_add_dispatch 00044 #ifdef _GLIBCXX_ATOMIC_BUILTINS 00045 static inline _Atomic_word 00046 __exchange_and_add(volatile _Atomic_word* __mem, int __val) 00047 { return __atomic_fetch_add(__mem, __val, __ATOMIC_ACQ_REL); } 00048 00049 static inline void 00050 __atomic_add(volatile _Atomic_word* __mem, int __val) 00051 { __atomic_fetch_add(__mem, __val, __ATOMIC_ACQ_REL); } 00052 #else 00053 _Atomic_word 00054 __attribute__ ((__unused__)) 00055 __exchange_and_add(volatile _Atomic_word*, int) throw (); 00056 00057 void 00058 __attribute__ ((__unused__)) 00059 __atomic_add(volatile _Atomic_word*, int) throw (); 00060 #endif 00061 00062 static inline _Atomic_word 00063 __exchange_and_add_single(_Atomic_word* __mem, int __val) 00064 { 00065 _Atomic_word __result = *__mem; 00066 *__mem += __val; 00067 return __result; 00068 } 00069 00070 static inline void 00071 __atomic_add_single(_Atomic_word* __mem, int __val) 00072 { *__mem += __val; } 00073 00074 static inline _Atomic_word 00075 __attribute__ ((__unused__)) 00076 __exchange_and_add_dispatch(_Atomic_word* __mem, int __val) 00077 { 00078 #ifdef __GTHREADS 00079 if (__gthread_active_p()) 00080 return __exchange_and_add(__mem, __val); 00081 else 00082 return __exchange_and_add_single(__mem, __val); 00083 #else 00084 return __exchange_and_add_single(__mem, __val); 00085 #endif 00086 } 00087 00088 static inline void 00089 __attribute__ ((__unused__)) 00090 __atomic_add_dispatch(_Atomic_word* __mem, int __val) 00091 { 00092 #ifdef __GTHREADS 00093 if (__gthread_active_p()) 00094 __atomic_add(__mem, __val); 00095 else 00096 __atomic_add_single(__mem, __val); 00097 #else 00098 __atomic_add_single(__mem, __val); 00099 #endif 00100 } 00101 00102 _GLIBCXX_END_NAMESPACE_VERSION 00103 } // namespace 00104 00105 // Even if the CPU doesn't need a memory barrier, we need to ensure 00106 // that the compiler doesn't reorder memory accesses across the 00107 // barriers. 00108 #ifndef _GLIBCXX_READ_MEM_BARRIER 00109 #define _GLIBCXX_READ_MEM_BARRIER __asm __volatile ("":::"memory") 00110 #endif 00111 #ifndef _GLIBCXX_WRITE_MEM_BARRIER 00112 #define _GLIBCXX_WRITE_MEM_BARRIER __asm __volatile ("":::"memory") 00113 #endif 00114 00115 #endif