1 // Low-level functions for atomic operations: x86, x >= 3 version -*- C++ -*- 2 3 // Copyright (C) 2003, 2004, 2005 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 2, 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 // You should have received a copy of the GNU General Public License along 17 // with this library; see the file COPYING. If not, write to the Free 18 // Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, 19 // USA. 20 21 // As a special exception, you may use this file as part of a free software 22 // library without restriction. Specifically, if other files instantiate 23 // templates or use macros or inline functions from this file, or you compile 24 // this file and link it with other files to produce an executable, this 25 // file does not by itself cause the resulting executable to be covered by 26 // the GNU General Public License. This exception does not however 27 // invalidate any other reasons why the executable file might be covered by 28 // the GNU General Public License. 29 30 #include <ext/atomicity.h> 31 32 _GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx) 33 34 template<int __inst> 35 struct _Atomicity_lock 36 { 37 static volatile _Atomic_word _S_atomicity_lock; 38 }; 39 40 template<int __inst> 41 volatile _Atomic_word _Atomicity_lock<__inst>::_S_atomicity_lock = 0; 42 43 template volatile _Atomic_word _Atomicity_lock<0>::_S_atomicity_lock; 44 45 _Atomic_word 46 __attribute__ ((__unused__)) 47 __exchange_and_add(volatile _Atomic_word* __mem, int __val) 48 { 49 register _Atomic_word __result, __tmp = 1; 50 51 // Obtain the atomic exchange/add spin lock. 52 do 53 { 54 __asm__ __volatile__ ("xchg{l} {%0,%1|%1,%0}" 55 : "=m" (_Atomicity_lock<0>::_S_atomicity_lock), 56 "+r" (__tmp) 57 : "m" (_Atomicity_lock<0>::_S_atomicity_lock)); 58 } 59 while (__tmp); 60 61 __result = *__mem; 62 *__mem += __val; 63 64 // Release spin lock. 65 _Atomicity_lock<0>::_S_atomicity_lock = 0; 66 67 return __result; 68 } 69 70 void 71 __attribute__ ((__unused__)) 72 __atomic_add(volatile _Atomic_word* __mem, int __val) 73 { __exchange_and_add(__mem, __val); } 74 75 _GLIBCXX_END_NAMESPACE 76