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/*
* 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/ext/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_