1 // Low-level functions for atomic operations: x86, x >= 3 version -*- C++ -*- 2 3 // Copyright (C) 2003, 2004, 2005, 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 #include <ext/atomicity.h> 26 27 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default) 28 { 29 _GLIBCXX_BEGIN_NAMESPACE_VERSION 30 31 template<int __inst> 32 struct _Atomicity_lock 33 { 34 static volatile _Atomic_word _S_atomicity_lock; 35 }; 36 37 template<int __inst> 38 volatile _Atomic_word _Atomicity_lock<__inst>::_S_atomicity_lock = 0; 39 40 template volatile _Atomic_word _Atomicity_lock<0>::_S_atomicity_lock; 41 42 _Atomic_word 43 __attribute__ ((__unused__)) 44 __exchange_and_add(volatile _Atomic_word* __mem, int __val) throw () 45 { 46 register _Atomic_word __result, __tmp = 1; 47 48 // Obtain the atomic exchange/add spin lock. 49 do 50 { 51 __asm__ __volatile__ ("xchg{l} {%0,%1|%1,%0}" 52 : "=m" (_Atomicity_lock<0>::_S_atomicity_lock), 53 "+r" (__tmp) 54 : "m" (_Atomicity_lock<0>::_S_atomicity_lock)); 55 } 56 while (__tmp); 57 58 __result = *__mem; 59 *__mem += __val; 60 61 // Release spin lock. 62 _Atomicity_lock<0>::_S_atomicity_lock = 0; 63 64 return __result; 65 } 66 67 void 68 __attribute__ ((__unused__)) 69 __atomic_add(volatile _Atomic_word* __mem, int __val) throw () 70 { __exchange_and_add(__mem, __val); } 71 72 _GLIBCXX_END_NAMESPACE_VERSION 73 } // namespace 74