Martin Stjernholm | c15e7e4 | 2020-12-02 22:50:53 +0000 | [diff] [blame] | 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_LIBARTBASE_BASE_ATOMIC_H_ |
| 18 | #define ART_LIBARTBASE_BASE_ATOMIC_H_ |
| 19 | |
| 20 | #include <stdint.h> |
| 21 | #include <atomic> |
| 22 | #include <limits> |
| 23 | #include <vector> |
| 24 | |
| 25 | #include <android-base/logging.h> |
| 26 | |
| 27 | #include "macros.h" |
| 28 | |
| 29 | namespace art { |
| 30 | |
| 31 | enum class CASMode { |
| 32 | kStrong, |
| 33 | kWeak, |
| 34 | }; |
| 35 | |
| 36 | template<typename T> |
| 37 | class PACKED(sizeof(T)) Atomic : public std::atomic<T> { |
| 38 | public: |
| 39 | Atomic<T>() : std::atomic<T>(T()) { } |
| 40 | |
| 41 | explicit Atomic<T>(T value) : std::atomic<T>(value) { } |
| 42 | |
| 43 | // Load data from an atomic variable with Java data memory order semantics. |
| 44 | // |
| 45 | // Promises memory access semantics of ordinary Java data. |
| 46 | // Does not order other memory accesses. |
| 47 | // Long and double accesses may be performed 32 bits at a time. |
| 48 | // There are no "cache coherence" guarantees; e.g. loads from the same location may be reordered. |
| 49 | // In contrast to normal C++ accesses, racing accesses are allowed. |
| 50 | T LoadJavaData() const { |
| 51 | return this->load(std::memory_order_relaxed); |
| 52 | } |
| 53 | |
| 54 | // Store data in an atomic variable with Java data memory ordering semantics. |
| 55 | // |
| 56 | // Promises memory access semantics of ordinary Java data. |
| 57 | // Does not order other memory accesses. |
| 58 | // Long and double accesses may be performed 32 bits at a time. |
| 59 | // There are no "cache coherence" guarantees; e.g. loads from the same location may be reordered. |
| 60 | // In contrast to normal C++ accesses, racing accesses are allowed. |
| 61 | void StoreJavaData(T desired_value) { |
| 62 | this->store(desired_value, std::memory_order_relaxed); |
| 63 | } |
| 64 | |
| 65 | // Atomically replace the value with desired_value if it matches the expected_value. |
| 66 | // Participates in total ordering of atomic operations. |
| 67 | bool CompareAndSetStrongSequentiallyConsistent(T expected_value, T desired_value) { |
| 68 | return this->compare_exchange_strong(expected_value, desired_value, std::memory_order_seq_cst); |
| 69 | } |
| 70 | |
| 71 | // The same, except it may fail spuriously. |
| 72 | bool CompareAndSetWeakSequentiallyConsistent(T expected_value, T desired_value) { |
| 73 | return this->compare_exchange_weak(expected_value, desired_value, std::memory_order_seq_cst); |
| 74 | } |
| 75 | |
| 76 | // Atomically replace the value with desired_value if it matches the expected_value. Doesn't |
| 77 | // imply ordering or synchronization constraints. |
| 78 | bool CompareAndSetStrongRelaxed(T expected_value, T desired_value) { |
| 79 | return this->compare_exchange_strong(expected_value, desired_value, std::memory_order_relaxed); |
| 80 | } |
| 81 | |
| 82 | // Atomically replace the value with desired_value if it matches the expected_value. Prior writes |
| 83 | // to other memory locations become visible to the threads that do a consume or an acquire on the |
| 84 | // same location. |
| 85 | bool CompareAndSetStrongRelease(T expected_value, T desired_value) { |
| 86 | return this->compare_exchange_strong(expected_value, desired_value, std::memory_order_release); |
| 87 | } |
| 88 | |
| 89 | // The same, except it may fail spuriously. |
| 90 | bool CompareAndSetWeakRelaxed(T expected_value, T desired_value) { |
| 91 | return this->compare_exchange_weak(expected_value, desired_value, std::memory_order_relaxed); |
| 92 | } |
| 93 | |
| 94 | // Atomically replace the value with desired_value if it matches the expected_value. Prior writes |
| 95 | // made to other memory locations by the thread that did the release become visible in this |
| 96 | // thread. |
| 97 | bool CompareAndSetWeakAcquire(T expected_value, T desired_value) { |
| 98 | return this->compare_exchange_weak(expected_value, desired_value, std::memory_order_acquire); |
| 99 | } |
| 100 | |
| 101 | // Atomically replace the value with desired_value if it matches the expected_value. Prior writes |
| 102 | // to other memory locations become visible to the threads that do a consume or an acquire on the |
| 103 | // same location. |
| 104 | bool CompareAndSetWeakRelease(T expected_value, T desired_value) { |
| 105 | return this->compare_exchange_weak(expected_value, desired_value, std::memory_order_release); |
| 106 | } |
| 107 | |
| 108 | bool CompareAndSet(T expected_value, |
| 109 | T desired_value, |
| 110 | CASMode mode, |
| 111 | std::memory_order memory_order) { |
| 112 | return mode == CASMode::kStrong |
| 113 | ? this->compare_exchange_strong(expected_value, desired_value, memory_order) |
| 114 | : this->compare_exchange_weak(expected_value, desired_value, memory_order); |
| 115 | } |
| 116 | |
| 117 | // Returns the address of the current atomic variable. This is only used by futex() which is |
| 118 | // declared to take a volatile address (see base/mutex-inl.h). |
| 119 | volatile T* Address() { |
| 120 | return reinterpret_cast<T*>(this); |
| 121 | } |
| 122 | |
| 123 | static T MaxValue() { |
| 124 | return std::numeric_limits<T>::max(); |
| 125 | } |
| 126 | }; |
| 127 | |
Martin Stjernholm | 413b2b5 | 2021-11-15 13:56:19 +0000 | [diff] [blame] | 128 | using AtomicInteger = Atomic<int32_t>; |
Martin Stjernholm | c15e7e4 | 2020-12-02 22:50:53 +0000 | [diff] [blame] | 129 | |
| 130 | static_assert(sizeof(AtomicInteger) == sizeof(int32_t), "Weird AtomicInteger size"); |
| 131 | static_assert(alignof(AtomicInteger) == alignof(int32_t), |
| 132 | "AtomicInteger alignment differs from that of underlyingtype"); |
| 133 | static_assert(sizeof(Atomic<int64_t>) == sizeof(int64_t), "Weird Atomic<int64> size"); |
| 134 | |
| 135 | // Assert the alignment of 64-bit integers is 64-bit. This isn't true on certain 32-bit |
| 136 | // architectures (e.g. x86-32) but we know that 64-bit integers here are arranged to be 8-byte |
| 137 | // aligned. |
| 138 | #if defined(__LP64__) |
| 139 | static_assert(alignof(Atomic<int64_t>) == alignof(int64_t), |
| 140 | "Atomic<int64> alignment differs from that of underlying type"); |
| 141 | #endif |
| 142 | |
| 143 | } // namespace art |
| 144 | |
| 145 | #endif // ART_LIBARTBASE_BASE_ATOMIC_H_ |