Atomic.h revision 4dd72631b5fcdcc4b21d096d27021801e2f8df1c 
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/*
18 * Atomic operations
19 */
20#ifndef _DALVIK_ATOMIC
21#define _DALVIK_ATOMIC
22
23#include <cutils/atomic.h>          /* use common Android atomic ops */
24#include <cutils/atomic-inline.h>   /* and some uncommon ones */
25
26/*
27 * Full memory barrier.  Ensures compiler ordering and SMP behavior.
28 */
29#define MEM_BARRIER()   ANDROID_MEMBAR_FULL()
30
31/*
32 * 32-bit atomic compare-and-swap macro.  Performs a memory barrier
33 * before the swap (store-release).
34 *
35 * If *_addr equals "_old", replace it with "_new" and return nonzero
36 * (i.e. returns "false" if the operation fails).
37 *
38 * Underlying function is currently declared:
39 *   int release_cas(int32_t old, int32_t new, volatile int32_t* addr)
40 *
41 * TODO: rename macro to ATOMIC_RELEASE_CAS
42 */
43#define ATOMIC_CMP_SWAP(_addr, _old, _new) \
44            (android_atomic_release_cas((_old), (_new), (_addr)) == 0)
45
46
47/*
48 * NOTE: Two "quasiatomic" operations on the exact same memory address
49 * are guaranteed to operate atomically with respect to each other,
50 * but no guarantees are made about quasiatomic operations mixed with
51 * non-quasiatomic operations on the same address, nor about
52 * quasiatomic operations that are performed on partially-overlapping
53 * memory.
54 */
55
56/*
57 * TODO: rename android_quasiatomic_* to dvmQuasiatomic*.  Don't want to do
58 * that yet due to branch merge issues.
59 */
60int64_t android_quasiatomic_swap_64(int64_t value, volatile int64_t* addr);
61int64_t android_quasiatomic_read_64(volatile int64_t* addr);
62int android_quasiatomic_cmpxchg_64(int64_t oldvalue, int64_t newvalue,
63        volatile int64_t* addr);
64
65#endif /*_DALVIK_ATOMIC*/
66