AuroraRuntime/Source/Threading/Primitives/AuConditionVariable.Generic.cpp

/***
    Copyright (C) 2021-2024 J Reece Wilson (a/k/a "Reece"). All rights reserved.

    File: AuConditionVariable.Generic.cpp
    Date: 2021-6-14
    Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include <Source/Threading/AuWaitFor.hpp>
#include "AuConditionVariable.Generic.hpp"
#include "../AuWakeInternal.hpp"
#include "SMTYield.hpp"

#if defined(_AURUNTIME_GENERICCV)

namespace Aurora::Threading::Primitives
{
    ConditionVariableGeneric::ConditionVariableGeneric()
    {

    }

    ConditionVariableGeneric::~ConditionVariableGeneric()
    {

    }

    bool ConditionVariableGeneric::WaitForSignalNsEx(GenericConditionMutex *pMutex, AuUInt64 qwTimeoutRelative, bool bSpin)
    {
        AuAtomicAdd(&this->uSleeping_, 1u);

        if (pMutex)
        {
            pMutex->Unlock();
        }

        auto bSuccess = this->WaitOne(qwTimeoutRelative, bSpin);
        if (!bSuccess)
        {
            auto uWaiters = this->uSleeping_;
            auto uWaitCount = 1;

            while (uWaiters &&
                   AuAtomicCompareExchange(&this->uSleeping_, uWaiters - uWaitCount, uWaiters) != uWaiters)
            {
                uWaiters = this->uSleeping_;

                if (uWaiters == 0)
                {
                    break;
                }
            }
        }

        if (pMutex)
        {
            pMutex->Lock();
        }

        return bSuccess;
    }

    void ConditionVariableGeneric::Signal()
    {
        AuUInt32 uWaiters {};

        uWaiters = AuAtomicLoad(&this->uSleeping_);
        if (uWaiters == 0)
        {
            return;
        }

        AuAtomicAdd(&this->uState_, 1u);
        InternalLTSWakeOne(&this->uState_);

        while (uWaiters &&
               AuAtomicCompareExchange(&this->uSleeping_, uWaiters - 1u, uWaiters) != uWaiters)
        {
            uWaiters = this->uSleeping_;

            if (uWaiters == 0)
            {
                return;
            }
        }
    }

    void ConditionVariableGeneric::Broadcast()
    {
        AuUInt32 uWaitCount {};
        AuUInt32 uWaiters {};

        while_bc (uWaiters = AuAtomicLoad(&this->uSleeping_))
        {
            AuAtomicAdd(&this->uState_, uWaiters);
            InternalLTSWakeCount(&this->uState_, uWaiters);
            uWaitCount = uWaiters;

            while (uWaiters &&
                   AuAtomicCompareExchange(&this->uSleeping_, uWaiters - uWaitCount, uWaiters) != uWaiters)
            {
                uWaiters = AuAtomicLoad(&this->uSleeping_);

                if (uWaiters <= uWaitCount)
                {
                    uWaitCount = uWaiters;
                }
            }
        }
    }

    bool ConditionVariableGeneric::WaitOne(AuUInt64 qwTimeoutRelative, bool bSpin)
    {
        AuUInt64 uStart {};
        AuUInt64 uEnd {};

        if (qwTimeoutRelative != 0)
        {
            uStart = AuTime::SteadyClockNS();
            uEnd   = uStart + qwTimeoutRelative;
        }

        if (bSpin ? this->TryTakeOneSpin() : this->TryTakeOneNoSpin())
        {
            return true;
        }

        auto old = this->uState_;
        while (!((old != 0) &&
               (AuAtomicCompareExchange(&this->uState_, old - 1, old) == old)))
        {
            static const AuUInt32 kRef { 0 };

            if (qwTimeoutRelative != 0)
            {
                if (!InternalLTSWaitOnAddressHighRes(&this->uState_, &kRef, 4, uEnd))
                {
                    return false;
                }
            }
            else
            {
                (void)InternalLTSWaitOnAddressHighRes(&this->uState_, &kRef, 4, uEnd);
            }

            old = this->uState_;
        }

        return true;
    }

    bool ConditionVariableGeneric::TryTakeOneNoSpin()
    {
        auto old = this->uState_;
        return old != 0 && AuAtomicCompareExchange(&this->uState_, old - 1, old) == old;
    }

    bool ConditionVariableGeneric::TryTakeOneSpin()
    {
        if (ThrdCfg::gPreferUnixPrimitivesNoSpin)
        {
            return this->TryTakeOneNoSpin();
        }

        return DoTryIfAlderLake([=]()
        {
            return this->TryTakeOneNoSpin();
        }, &this->uState_);
    }

    AUKN_SYM IConditionVariable *ConditionVariableNew(const AuSPtr<IConditionMutex> &pMutex)
    {
        return _new ConditionVariableGenericImpl(pMutex);
    }

    AUKN_SYM void ConditionVariableRelease(IConditionVariable *pCV)
    {
        AuSafeDelete<ConditionVariableGenericImpl *>(pCV);
    }

    AUROXTL_INTERFACE_SOO_SRC(ConditionVariable, ConditionVariableGenericImpl, (const AuSPtr<IConditionMutex> &, pMutex))
}

#endif