/* * Copyright (C) 2019 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 SRC_PROFILING_MEMORY_SCOPED_SPINLOCK_H_ #define SRC_PROFILING_MEMORY_SCOPED_SPINLOCK_H_ #include "perfetto/base/logging.h" #include "perfetto/base/utils.h" #include <atomic> #include <new> #include <utility> namespace perfetto { namespace profiling { class ScopedSpinlock { public: enum class Mode { // Try for a fixed number of attempts, then return an unlocked handle. Try, // Keep spinning until successful. Blocking }; ScopedSpinlock(std::atomic<bool>* lock, Mode mode) : lock_(lock) { if (PERFETTO_LIKELY(!lock_->exchange(true, std::memory_order_acquire))) { locked_ = true; return; } LockSlow(mode); } ScopedSpinlock(const ScopedSpinlock&) = delete; ScopedSpinlock& operator=(const ScopedSpinlock&) = delete; ScopedSpinlock(ScopedSpinlock&& other) noexcept : lock_(other.lock_), locked_(other.locked_) { other.locked_ = false; } ScopedSpinlock& operator=(ScopedSpinlock&& other) { if (this != &other) { this->~ScopedSpinlock(); new (this) ScopedSpinlock(std::move(other)); } return *this; } ~ScopedSpinlock() { Unlock(); } void Unlock() { if (locked_) { PERFETTO_DCHECK(lock_->load()); lock_->store(false, std::memory_order_release); } locked_ = false; } bool locked() const { return locked_; } private: void LockSlow(Mode mode); std::atomic<bool>* lock_; bool locked_ = false; }; } // namespace profiling } // namespace perfetto #endif // SRC_PROFILING_MEMORY_SCOPED_SPINLOCK_H_