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 24 namespace 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. 32 class 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
