atomic.h revision 4f6e8d7a00cbeda1e70cc15be9c4af1018bdad53 
1/*
2 * Copyright (C) 2007 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#ifndef ANDROID_CUTILS_ATOMIC_H
18#define ANDROID_CUTILS_ATOMIC_H
19
20#include <stdint.h>
21#include <sys/types.h>
22
23#ifdef __cplusplus
24extern "C" {
25#endif
26
27/*
28 * NOTE: memory shared between threads is synchronized by all atomic operations
29 * below, this means that no explicit memory barrier is required: all reads or
30 * writes issued before android_atomic_* operations are guaranteed to complete
31 * before the atomic operation takes place.
32 */
33
34void android_atomic_write(int32_t value, volatile int32_t* addr);
35
36/*
37 * all these atomic operations return the previous value
38 */
39
40
41int32_t android_atomic_inc(volatile int32_t* addr);
42int32_t android_atomic_dec(volatile int32_t* addr);
43
44int32_t android_atomic_add(int32_t value, volatile int32_t* addr);
45int32_t android_atomic_and(int32_t value, volatile int32_t* addr);
46int32_t android_atomic_or(int32_t value, volatile int32_t* addr);
47
48int32_t android_atomic_swap(int32_t value, volatile int32_t* addr);
49
50/*
51 * NOTE: Two "quasiatomic" operations on the exact same memory address
52 * are guaranteed to operate atomically with respect to each other,
53 * but no guarantees are made about quasiatomic operations mixed with
54 * non-quasiatomic operations on the same address, nor about
55 * quasiatomic operations that are performed on partially-overlapping
56 * memory.
57 */
58
59int64_t android_quasiatomic_swap_64(int64_t value, volatile int64_t* addr);
60int64_t android_quasiatomic_read_64(volatile int64_t* addr);
61
62/*
63 * cmpxchg return a non zero value if the exchange was NOT performed,
64 * in other words if oldvalue != *addr
65 */
66
67int android_atomic_cmpxchg(int32_t oldvalue, int32_t newvalue,
68        volatile int32_t* addr);
69
70int android_quasiatomic_cmpxchg_64(int64_t oldvalue, int64_t newvalue,
71        volatile int64_t* addr);
72
73
74
75#ifdef __cplusplus
76} // extern "C"
77#endif
78
79#endif // ANDROID_CUTILS_ATOMIC_H
80