// Licensed to the Apache Software Foundation (ASF) under one

// or more contributor license agreements.  See the NOTICE file

// distributed with this work for additional information

// regarding copyright ownership.  The ASF licenses this file

// to you 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.

// This file is copied from

// https://github.com/apache/impala/blob/branch-2.9.0/be/src/util/spinlock.h

// and modified by Doris

#pragma once

#include <sched.h> /* For sched_yield() */

#include <atomic>

namespace doris {

// Lightweight spinlock.

class SpinLock {

public:

    SpinLock() : _locked(false) {

        // do nothing

    }

    // Acquires the lock, spins until the lock becomes available

    void lock() {

        for (int spin_count = 0; !try_lock(); ++spin_count) {

            if (spin_count < NUM_SPIN_CYCLES) {

#if (defined(__i386) || defined(__x86_64__))

                asm volatile("pause\n" : : : "memory");

#elif defined(__aarch64__)

                asm volatile("yield\n" ::: "memory");

#endif

            } else {

                sched_yield();

                spin_count = 0;

            }

        }

    }

    void unlock() { _locked.clear(std::memory_order_release); }

    // Tries to acquire the lock

    bool try_lock() { return !_locked.test_and_set(std::memory_order_acquire); }

private:

    static const int NUM_SPIN_CYCLES = 70;

    std::atomic_flag _locked;

};

} // end namespace doris