libstdc++
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00001 // Support for atomic operations -*- C++ -*- 00002 00003 // Copyright (C) 2004, 2005, 2006, 2008, 2009 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 atomicity.h 00026 * This is an internal header file, included by other library headers. 00027 * You should not attempt to use it directly. 00028 */ 00029 00030 #ifndef _GLIBCXX_ATOMICITY_H 00031 #define _GLIBCXX_ATOMICITY_H 1 00032 00033 #include <bits/c++config.h> 00034 #include <bits/gthr.h> 00035 #include <bits/atomic_word.h> 00036 00037 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx) 00038 00039 // Functions for portable atomic access. 00040 // To abstract locking primitives across all thread policies, use: 00041 // __exchange_and_add_dispatch 00042 // __atomic_add_dispatch 00043 #ifdef _GLIBCXX_ATOMIC_BUILTINS_4 00044 static inline _Atomic_word 00045 __exchange_and_add(volatile _Atomic_word* __mem, int __val) 00046 { return __sync_fetch_and_add(__mem, __val); } 00047 00048 static inline void 00049 __atomic_add(volatile _Atomic_word* __mem, int __val) 00050 { __sync_fetch_and_add(__mem, __val); } 00051 #else 00052 _Atomic_word 00053 __attribute__ ((__unused__)) 00054 __exchange_and_add(volatile _Atomic_word*, int); 00055 00056 void 00057 __attribute__ ((__unused__)) 00058 __atomic_add(volatile _Atomic_word*, int); 00059 #endif 00060 00061 static inline _Atomic_word 00062 __exchange_and_add_single(_Atomic_word* __mem, int __val) 00063 { 00064 _Atomic_word __result = *__mem; 00065 *__mem += __val; 00066 return __result; 00067 } 00068 00069 static inline void 00070 __atomic_add_single(_Atomic_word* __mem, int __val) 00071 { *__mem += __val; } 00072 00073 static inline _Atomic_word 00074 __attribute__ ((__unused__)) 00075 __exchange_and_add_dispatch(_Atomic_word* __mem, int __val) 00076 { 00077 #ifdef __GTHREADS 00078 if (__gthread_active_p()) 00079 return __exchange_and_add(__mem, __val); 00080 else 00081 return __exchange_and_add_single(__mem, __val); 00082 #else 00083 return __exchange_and_add_single(__mem, __val); 00084 #endif 00085 } 00086 00087 static inline void 00088 __attribute__ ((__unused__)) 00089 __atomic_add_dispatch(_Atomic_word* __mem, int __val) 00090 { 00091 #ifdef __GTHREADS 00092 if (__gthread_active_p()) 00093 __atomic_add(__mem, __val); 00094 else 00095 __atomic_add_single(__mem, __val); 00096 #else 00097 __atomic_add_single(__mem, __val); 00098 #endif 00099 } 00100 00101 _GLIBCXX_END_NAMESPACE 00102 00103 // Even if the CPU doesn't need a memory barrier, we need to ensure 00104 // that the compiler doesn't reorder memory accesses across the 00105 // barriers. 00106 #ifndef _GLIBCXX_READ_MEM_BARRIER 00107 #define _GLIBCXX_READ_MEM_BARRIER __asm __volatile ("":::"memory") 00108 #endif 00109 #ifndef _GLIBCXX_WRITE_MEM_BARRIER 00110 #define _GLIBCXX_WRITE_MEM_BARRIER __asm __volatile ("":::"memory") 00111 #endif 00112 00113 #endif