1 // Support for atomic operations -*- C++ -*- 2 3 // Copyright (C) 2004, 2005, 2006, 2008, 2009 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 atomicity.h 26 * This is an internal header file, included by other library headers. 27 * You should not attempt to use it directly. 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 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx) 38 39 // Functions for portable atomic access. 40 // To abstract locking primitives across all thread policies, use: 41 // __exchange_and_add_dispatch 42 // __atomic_add_dispatch 43 #ifdef _GLIBCXX_ATOMIC_BUILTINS_4 44 static inline _Atomic_word 45 __exchange_and_add(volatile _Atomic_word* __mem, int __val) 46 { return __sync_fetch_and_add(__mem, __val); } 47 48 static inline void 49 __atomic_add(volatile _Atomic_word* __mem, int __val) 50 { __sync_fetch_and_add(__mem, __val); } 51 #else 52 _Atomic_word 53 __attribute__ ((__unused__)) 54 __exchange_and_add(volatile _Atomic_word*, int); 55 56 void 57 __attribute__ ((__unused__)) 58 __atomic_add(volatile _Atomic_word*, int); 59 #endif 60 61 static inline _Atomic_word 62 __exchange_and_add_single(_Atomic_word* __mem, int __val) 63 { 64 _Atomic_word __result = *__mem; 65 *__mem += __val; 66 return __result; 67 } 68 69 static inline void 70 __atomic_add_single(_Atomic_word* __mem, int __val) 71 { *__mem += __val; } 72 73 static inline _Atomic_word 74 __attribute__ ((__unused__)) 75 __exchange_and_add_dispatch(_Atomic_word* __mem, int __val) 76 { 77 #ifdef __GTHREADS 78 if (__gthread_active_p()) 79 return __exchange_and_add(__mem, __val); 80 else 81 return __exchange_and_add_single(__mem, __val); 82 #else 83 return __exchange_and_add_single(__mem, __val); 84 #endif 85 } 86 87 static inline void 88 __attribute__ ((__unused__)) 89 __atomic_add_dispatch(_Atomic_word* __mem, int __val) 90 { 91 #ifdef __GTHREADS 92 if (__gthread_active_p()) 93 __atomic_add(__mem, __val); 94 else 95 __atomic_add_single(__mem, __val); 96 #else 97 __atomic_add_single(__mem, __val); 98 #endif 99 } 100 101 _GLIBCXX_END_NAMESPACE 102 103 // Even if the CPU doesn't need a memory barrier, we need to ensure 104 // that the compiler doesn't reorder memory accesses across the 105 // barriers. 106 #ifndef _GLIBCXX_READ_MEM_BARRIER 107 #define _GLIBCXX_READ_MEM_BARRIER __asm __volatile ("":::"memory") 108 #endif 109 #ifndef _GLIBCXX_WRITE_MEM_BARRIER 110 #define _GLIBCXX_WRITE_MEM_BARRIER __asm __volatile ("":::"memory") 111 #endif 112 113 #endif 114
