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#ifndef ART_RUNTIME_ATOMIC_H_
18#define ART_RUNTIME_ATOMIC_H_
19
20#include <stdint.h>
21
22#include "base/macros.h"
23
24namespace art {
25
26// NOTE: Two "quasiatomic" operations on the exact same memory address
27// are guaranteed to operate atomically with respect to each other,
28// but no guarantees are made about quasiatomic operations mixed with
29// non-quasiatomic operations on the same address, nor about
30// quasiatomic operations that are performed on partially-overlapping
31// memory.
32class QuasiAtomic {
33 public:
34  static void Startup();
35
36  static void Shutdown();
37
38  // Reads the 64-bit value at "addr" without tearing.
39  static int64_t Read64(volatile const int64_t* addr);
40
41  // Writes to the 64-bit value at "addr" without tearing.
42  static void Write64(volatile int64_t* addr, int64_t val);
43
44  // Atomically compare the value at "addr" to "old_value", if equal replace it with "new_value"
45  // and return true. Otherwise, don't swap, and return false.
46  static bool Cas64(int64_t old_value, int64_t new_value, volatile int64_t* addr);
47
48  // Does the architecture provide reasonable atomic long operations or do we fall back on mutexes?
49  static bool LongAtomicsUseMutexes();
50
51 private:
52  DISALLOW_COPY_AND_ASSIGN(QuasiAtomic);
53};
54
55}  // namespace art
56
57#endif  // ART_RUNTIME_ATOMIC_H_
58