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/*
* Copyright (C) 2008 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef ART_RUNTIME_ATOMIC_H_
#define ART_RUNTIME_ATOMIC_H_
#include <stdint.h>
#include "base/macros.h"
namespace art {
// NOTE: Two "quasiatomic" operations on the exact same memory address
// are guaranteed to operate atomically with respect to each other,
// but no guarantees are made about quasiatomic operations mixed with
// non-quasiatomic operations on the same address, nor about
// quasiatomic operations that are performed on partially-overlapping
// memory.
class QuasiAtomic {
public:
static void Startup();
static void Shutdown();
// Reads the 64-bit value at "addr" without tearing.
static int64_t Read64(volatile const int64_t* addr);
// Writes to the 64-bit value at "addr" without tearing.
static void Write64(volatile int64_t* addr, int64_t val);
// Atomically compare the value at "addr" to "old_value", if equal replace it with "new_value"
// and return true. Otherwise, don't swap, and return false.
static bool Cas64(int64_t old_value, int64_t new_value, volatile int64_t* addr);
// Does the architecture provide reasonable atomic long operations or do we fall back on mutexes?
static bool LongAtomicsUseMutexes();
private:
DISALLOW_COPY_AND_ASSIGN(QuasiAtomic);
};
} // namespace art
#endif // ART_RUNTIME_ATOMIC_H_
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