1 // Low-level functions for atomic operations: x86, x >= 3 version -*- C++ -*- 2 3 // Copyright (C) 2003 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, 59 Temple Place - Suite 330, Boston, MA 02111-1307, 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 #ifndef _BITS_ATOMICITY_H 31 #define _BITS_ATOMICITY_H 1 32 33 typedef int _Atomic_word; 34 35 template <int __inst> 36 struct __Atomicity_lock 37 { 38 static volatile _Atomic_word _S_atomicity_lock; 39 }; 40 41 template <int __inst> 42 volatile _Atomic_word __Atomicity_lock<__inst>::_S_atomicity_lock = 0; 43 44 template volatile _Atomic_word __Atomicity_lock<0>::_S_atomicity_lock; 45 46 static inline _Atomic_word 47 __attribute__ ((__unused__)) 48 __exchange_and_add (volatile _Atomic_word *__mem, int __val) 49 { 50 register _Atomic_word __result, __tmp = 1; 51 52 /* obtain the atomic exchange/add spin lock */ 53 do { 54 __asm__ __volatile__ ("xchg{l} {%0,%1|%1,%0}" 55 : "+m" (__Atomicity_lock<0>::_S_atomicity_lock), 56 "+r" (__tmp)); 57 } while (__tmp); 58 59 __result = *__mem; 60 *__mem += __val; 61 62 /* release spin lock */ 63 __Atomicity_lock<0>::_S_atomicity_lock = 0; 64 65 return __result; 66 } 67 68 static inline void 69 __attribute__ ((__unused__)) 70 __atomic_add (volatile _Atomic_word* __mem, int __val) 71 { 72 __exchange_and_add (__mem, __val); 73 } 74 75 #endif /* atomicity.h */ 76