1 /* 2 * Copyright (C) 2008 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 /* 17 * Atomic operations 18 */ 19 #ifndef _DALVIK_ATOMIC 20 #define _DALVIK_ATOMIC 21 22 #include <utils/Atomic.h> /* use common Android atomic ops */ 23 24 /* 25 * Memory barrier. Guarantee that register-resident variables 26 * are flushed to memory, and guarantee that instructions before 27 * the barrier do not get reordered to appear past it. 28 * 29 * 'asm volatile ("":::"memory")' is probably overkill, but it's correct. 30 * There may be a way to do it that doesn't flush every single register. 31 * 32 * TODO: look into the wmb() family on Linux and equivalents on other systems. 33 */ 34 #define MEM_BARRIER() do { asm volatile ("":::"memory"); } while (0) 35 36 /* 37 * Atomic compare-and-swap macro. 38 * 39 * If *_addr equals "_old", replace it with "_new" and return 1. Otherwise 40 * return 0. (e.g. x86 "cmpxchgl" instruction.) 41 * 42 * Underlying function is currently declared: 43 * int android_atomic_cmpxchg(int32_t old, int32_t new, volatile int32_t* addr) 44 */ 45 #define ATOMIC_CMP_SWAP(_addr, _old, _new) \ 46 (android_atomic_cmpxchg((_old), (_new), (_addr)) == 0) 47 48 #endif /*_DALVIK_ATOMIC*/ 49
