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 #include <bits/c++config.h> 33 #include <bits/gthr.h> 34 #include <bits/atomic_word.h> 35 36 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default) 37 { 38 _GLIBCXX_BEGIN_NAMESPACE_VERSION 39 40 // Functions for portable atomic access. 41 // To abstract locking primitives across all thread policies, use: 42 // __exchange_and_add_dispatch 43 // __atomic_add_dispatch 44 #if defined(_GLIBCXX_ATOMIC_BUILTINS) && (!defined(__clang__) || defined(__i386__)) 45 // NOTE: clang arm/mips can't compile the following two library calls yet. 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
