1 /* 2 * Copyright (C) 2019 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 SRC_PROFILING_MEMORY_SCOPED_SPINLOCK_H_ 18 #define SRC_PROFILING_MEMORY_SCOPED_SPINLOCK_H_ 19 20 #include "perfetto/base/logging.h" 21 #include "perfetto/base/utils.h" 22 23 #include <atomic> 24 #include <new> 25 #include <utility> 26 27 namespace perfetto { 28 namespace profiling { 29 30 class ScopedSpinlock { 31 public: 32 enum class Mode { 33 // Try for a fixed number of attempts, then return an unlocked handle. 34 Try, 35 // Keep spinning until successful. 36 Blocking 37 }; 38 ScopedSpinlock(std::atomic<bool> * lock,Mode mode)39 ScopedSpinlock(std::atomic<bool>* lock, Mode mode) : lock_(lock) { 40 if (PERFETTO_LIKELY(!lock_->exchange(true, std::memory_order_acquire))) { 41 locked_ = true; 42 return; 43 } 44 LockSlow(mode); 45 } 46 47 ScopedSpinlock(const ScopedSpinlock&) = delete; 48 ScopedSpinlock& operator=(const ScopedSpinlock&) = delete; 49 ScopedSpinlock(ScopedSpinlock && other)50 ScopedSpinlock(ScopedSpinlock&& other) noexcept 51 : lock_(other.lock_), locked_(other.locked_) { 52 other.locked_ = false; 53 } 54 55 ScopedSpinlock& operator=(ScopedSpinlock&& other) { 56 if (this != &other) { 57 this->~ScopedSpinlock(); 58 new (this) ScopedSpinlock(std::move(other)); 59 } 60 return *this; 61 } 62 ~ScopedSpinlock()63 ~ScopedSpinlock() { Unlock(); } 64 Unlock()65 void Unlock() { 66 if (locked_) { 67 PERFETTO_DCHECK(lock_->load()); 68 lock_->store(false, std::memory_order_release); 69 } 70 locked_ = false; 71 } 72 locked()73 bool locked() const { return locked_; } 74 75 private: 76 void LockSlow(Mode mode); 77 std::atomic<bool>* lock_; 78 bool locked_ = false; 79 }; 80 81 } // namespace profiling 82 } // namespace perfetto 83 84 #endif // SRC_PROFILING_MEMORY_SCOPED_SPINLOCK_H_ 85