AuroraRuntime/Source/Threading/Primitives/AuSpinLock.cpp

/***
    Copyright (C) 2021 J Reece Wilson (a/k/a "Reece"). All rights reserved.

    File: AuSpinLock.cpp
    Date: 2021-6-12
    Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include "AuSpinLock.hpp"
#include "SMTYield.hpp"

namespace Aurora::Threading::Primitives
{
    static void YieldCpu(long &count)
    {
        int loops = (1 << count);
        while (loops > 0)
        {
            SMPPause();
            loops -= 1;
        }
        count++;
        if (count >= 15) count = 0;
    }

    SpinLock::SpinLock()
    {
        state_ = 0;
    }

    bool SpinLock::HasOSHandle(AuMach &mach)
    {
        return false;
    }

    bool SpinLock::TryLock()
    {
        return AuAtomicTestAndSet(&this->state_, 0) == 0;
    }

    bool SpinLock::HasLockImplementation()
    {
        return true;
    }

    void SpinLock::SlowLock()
    {
        auto status = LockNS(0);
        SysAssert(status, "Couldn't lock Mutex object");
    }

    bool SpinLock::LockNS(AuUInt64 timeout)
    {
        if (timeout == 0)
        {
            while (AuAtomicTestAndSet(&this->state_, 0))
            {
                long count = 0;
                while (this->state_)
                {
                    YieldCpu(count);
                }
            }
        }
        else
        {
            AuUInt64 startTime = AuTime::SteadyClockNS();
            AuUInt64 endTime   = startTime + timeout;

            while (AuAtomicTestAndSet(&this->state_, 0))
            {
                long count = 0;
                while (this->state_)
                {
                    if (endTime <= AuTime::SteadyClockNS())
                    {
                        return false;
                    }
                    YieldCpu(count);
                }
            }
        }

        return true;
    }

    bool SpinLock::LockMS(AuUInt64 timeout)
    {
        return LockNS(AuMSToNS<AuUInt64>(timeout));
    }

    void SpinLock::Unlock()
    {
        this->state_ = 0;
    }
}