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 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx) 28 29 template<int __inst> 30 struct _Atomicity_lock 31 { 32 static volatile _Atomic_word _S_atomicity_lock; 33 }; 34 35 template<int __inst> 36 volatile _Atomic_word _Atomicity_lock<__inst>::_S_atomicity_lock = 0; 37 38 template volatile _Atomic_word _Atomicity_lock<0>::_S_atomicity_lock; 39 40 _Atomic_word 41 __attribute__ ((__unused__)) 42 __exchange_and_add(volatile _Atomic_word* __mem, int __val) throw () 43 { 44 register _Atomic_word __result, __tmp = 1; 45 46 // Obtain the atomic exchange/add spin lock. 47 do 48 { 49 __asm__ __volatile__ ("xchg{l} {%0,%1|%1,%0}" 50 : "=m" (_Atomicity_lock<0>::_S_atomicity_lock), 51 "+r" (__tmp) 52 : "m" (_Atomicity_lock<0>::_S_atomicity_lock)); 53 } 54 while (__tmp); 55 56 __result = *__mem; 57 *__mem += __val; 58 59 // Release spin lock. 60 _Atomicity_lock<0>::_S_atomicity_lock = 0; 61 62 return __result; 63 } 64 65 void 66 __attribute__ ((__unused__)) 67 __atomic_add(volatile _Atomic_word* __mem, int __val) throw () 68 { __exchange_and_add(__mem, __val); } 69 70 _GLIBCXX_END_NAMESPACE 71