AuroraRuntime/Source/Async/ThreadPool.cpp

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

    File: ThreadPool.cpp
    Date: 2021-10-30
    Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include "Async.hpp"
#include "ThreadPool.hpp"
#include "AsyncApp.hpp"
#include "WorkItem.hpp"
#include "AuSchedular.hpp"
#include "ThreadWorkerQueueShim.hpp"
#include "IAsyncRunnable.hpp"
#include "AuAsyncFuncRunnable.hpp"
#include "AuAsyncFuncWorker.hpp"

namespace Aurora::Async
{
    //STATIC_TLS(WorkerId_t, tlsWorkerId);
    static thread_local AuWPtr<ThreadPool> tlsCurrentThreadPool;

    inline auto GetWorkerInternal(const AuSPtr<IThreadPool> &pool)
    {
        if (pool.get() == AuStaticCast<IAsyncApp>(gAsyncApp))
        {
            return AuUnsafeRaiiToShared(AuStaticCast<ThreadPool>(gAsyncApp));
        }

        return AuStaticPointerCast<ThreadPool>(pool);
    }

    AUKN_SYM WorkerPId_t GetCurrentWorkerPId()
    {
        auto lkPool = tlsCurrentThreadPool.lock();
        if (!lkPool)
        {
            return {};
        }

        auto cpy = *lkPool->tlsWorkerId;
        if (auto pPool = AuTryLockMemoryType(cpy.pool))
        {
            return WorkerPId_t(pPool, cpy);
        }
        else
        {
            return {};
        }
    }
    
    //

    ThreadPool::ThreadPool() : shutdownEvent_(false, false, true)
    {
        this->pRWReadView = this->rwlock_->AsReadable();
    }

    // internal pool interface

    bool ThreadPool::WaitFor(WorkerId_t unlocker, const AuSPtr<Threading::IWaitable> &primitive, AuUInt32 timeoutMs)
    {
        return WaitFor(WorkerPId_t { AuAsync::GetCurrentWorkerPId().GetPool(), unlocker }, primitive, timeoutMs);
    }

    bool ThreadPool::WaitFor(WorkerPId_t unlocker, const AuSPtr<Threading::IWaitable> &primitive, AuUInt32 timeoutMs)
    {
        if (auto pCurThread = GetThreadState())
        {
            bool bWorkerIdMatches = (unlocker.second == pCurThread->thread.id.second) ||
                                    ((unlocker.second == Async::kThreadIdAny) &&
                                     (GetThreadWorkersCount(unlocker.first) == 1));
                                  
            if ((unlocker.first == pCurThread->thread.id.first) &&
                (unlocker.GetPool().get() == this) &&
                (bWorkerIdMatches))
            {

                bool queryAsync = false;
                while (!(queryAsync ? primitive->TryLock() : Threading::WaitFor(primitive.get(), 2)))
                {
                    queryAsync = CtxYield();

                    if (!queryAsync && this->shuttingdown_)
                    {
                        return false;
                    }
                }

                return true;
            }
        }

        {
            AuSPtr<ThreadState> pHandle;

            if (auto pPool = unlocker)
            {
                auto pPoolEx = AuStaticCast<ThreadPool>(unlocker.GetPool());
                AU_LOCK_GUARD(pPoolEx->rwlock_->AsReadable());

                if ((pHandle = AuStaticCast<ThreadPool>(unlocker.GetPool())->GetThreadHandle(unlocker)))
                {
                    AU_LOCK_GUARD(pHandle->externalFencesLock);
                    if (pHandle->exitingflag2)
                    {
                        return primitive->TryLock();
                    }
                    else
                    {
                        pHandle->externalFences.push_back(primitive.get());
                    }
                }
                else if (unlocker.GetPool().get() == this)
                {
                    return primitive->LockMS(timeoutMs);
                }
            }

            bool bRet = Threading::WaitFor(primitive.get(), timeoutMs);

            if (pHandle)
            {
                AU_LOCK_GUARD(pHandle->externalFencesLock);
                AuTryRemove(pHandle->externalFences, primitive.get());
            }

            return bRet;
        }
    }

    void ThreadPool::Run(WorkerId_t target, AuSPtr<IAsyncRunnable> runnable)
    {
        return this->Run(target, runnable, true);
    }

    void ThreadPool::Run(WorkerId_t target, AuSPtr<IAsyncRunnable> runnable, bool bIncrement)
    {
        auto state = GetGroup(target.first);
        SysAssert(static_cast<bool>(state), "couldn't dispatch a task to an offline group");

        auto pWorker = state->GetThreadByIndex(target.second);
        if (!pWorker)
        {
            runnable->CancelAsync();
            return;
        }

        if (pWorker->shutdown.bDropSubmissions)
        {
            runnable->CancelAsync();
            return;
        }

        if (bIncrement)
        {
            AuAtomicAdd(&this->uAtomicCounter, 1u);
        }

        state->workQueue.AddWorkEntry(pWorker.get(), AuMakePair(target.second, runnable));

        if (target.second == Async::kThreadIdAny)
        {
            state->SignalAll();
        }
        else
        {
            pWorker->sync.SetEvent();
        }
    }

    IThreadPool *ThreadPool::ToThreadPool()
    {
        return this;
    }

    // ithreadpool

    size_t ThreadPool::GetThreadWorkersCount(ThreadGroup_t group)
    {
        return GetGroup(group)->workers.size();
    }

    void ThreadPool::SetRunningMode(bool eventRunning)
    {
        this->runnersRunning_ = eventRunning;
    }
    
    bool ThreadPool::Spawn(WorkerId_t workerId)
    {
        return Spawn(workerId, false);
    }
    
    bool ThreadPool::Create(WorkerId_t workerId)
    {
        return Spawn(workerId, true);
    }
    
    bool ThreadPool::InRunnerMode()
    {
        return this->runnersRunning_;
    }
    
    bool ThreadPool::Poll()
    {
        AuUInt32 uCount {};
        return InternalRunOne(GetThreadStateNoWarn(), false, uCount);
    }
    
    bool ThreadPool::RunOnce()
    {
        AuUInt32 uCount {};
        return InternalRunOne(GetThreadStateNoWarn(), true, uCount);
    }
    
    bool ThreadPool::Run()
    {
        bool ranOnce {};

        auto pJobRunner = GetThreadStateNoWarn();

        if (!pJobRunner)
        {
            this->shutdownEvent_->LockMS(0);
            return true;
        }

        auto oldTlsHandle = AuExchange(tlsCurrentThreadPool, AuSharedFromThis());
        auto auThread = AuThreads::GetThread();

        while ((!auThread->Exiting()) &&
               ((this->shuttingdown_ & 2) != 2) &&
               (!pJobRunner->shutdown.bBreakMainLoop))
        {
            AuUInt32 uCount {};

            // Do work (blocking)
            if (!InternalRunOne(pJobRunner, true, uCount))
            {
                if ((this->shuttingdown_ & 2) == 2)
                {
                    return ranOnce;
                }
            }
            ranOnce = true;
        }

        tlsCurrentThreadPool = oldTlsHandle;

        return ranOnce;
    }
    
    bool ThreadPool::InternalRunOne(AuSPtr<ThreadState> state, bool block, AuUInt32 &uCount)
    {
        if (!state)
        {
            SysPushErrorUninitialized("Not an async thread");
            return false;
        }

        bool bSuccess {};
        EarlyExitTick();

        {
            auto asyncLoop = state->asyncLoop;
            asyncLoop->OnFrame();

            if (asyncLoop->GetSourceCount() > 1)
            {
                if (block)
                {
                    asyncLoop->WaitAny(0);
                }
                else
                {
                    asyncLoop->PumpNonblocking();
                }
                
                bSuccess = PollInternal(state, false, uCount);
            }
            else
            {
                bSuccess = PollInternal(state, block, uCount);
            }
        }
        EarlyExitTick();

        return bSuccess;
    }

    bool ThreadPool::PollInternal(AuSPtr<ThreadState> state, bool block, AuUInt32 &uCount)
    {
        if (!state)
        {
            SysPushErrorUninitialized("Not an async thread");
            return false;
        }

        auto group = state->parent.lock();

        {
            AU_LOCK_GUARD(state->sync.cvWorkMutex);

            do
            {
                group->workQueue.Dequeue(state->pendingWorkItems, state->stackState.uWorkMultipopCount, state->thread.id.second);

                state->sync.UpdateCVState(state.get());

                // Consider blocking for more work
                if (!block)
                {
                    break;
                }

                // pre-wakeup thread terminating check
                if (state->thread.pThread->Exiting())
                {
                    break;
                }

                // Block if no work items are present
                if (state->pendingWorkItems.empty())
                {
                    if (this->shuttingdown_ & 2)
                    {
                        break;
                    }

                    state->sync.cvVariable->WaitForSignal();

                    if (this->shuttingdown_ & 2)
                    {
                        break;
                    }
                }

                // Post-wakeup thread terminating check
                if (state->thread.pThread->Exiting())
                {
                    break;
                }

                if (state->pendingWorkItems.empty() && (
                    (this->GetThreadState()->asyncLoop->GetSourceCount() > 1) ||
                    this->GetThreadState()->asyncLoop->CommitPending()))                    //(this->ToKernelWorkQueue()->IsSignaledPeek()))
                {
                    return false;
                }

            }
            while (state->pendingWorkItems.empty() && block);

            if (!block) // quick hack: is worthy of io reset by virtue of having polled externally (most likely for IO ticks, unlikely for intraprocess ticks)
            {
                AU_LOCK_GUARD(group->workQueue.mutex); // dont atomically increment our work counters [signal under mutex group]...
                AU_LOCK_GUARD(group->workersMutex);    // dont atomically increment our work counters [broadcast]...
                // ...these primitives are far less expensive to hit than resetting kernel primitives
                // AU_LOCK_GUARD(state->cvWorkMutex) used to protect us

                if (group->workQueue.IsEmpty(this, state->thread.id))
                {
                    state->sync.eventLs->Reset(); // ...until we're done
                    AuAtomicStore(&state->sync.cvLSActive, 0u);
                }
            }
        }

        if (state->pendingWorkItems.empty())
        {
            if (InRunnerMode())
            {
                if ((this->uAtomicCounter == 0) &&
                    this->IsDepleted())
                {
                    Shutdown();
                }
            }

            return false;
        }

        int runningTasks {};
        auto uStartCookie = state->stackState.uStackCookie++;

        // Account for 
        //            while (AuAsync.GetCurrentPool()->runForever());
        // in the first task (or deeper)
        if (InRunnerMode() && state->stackState.uStackCallDepth) // are we one call deep?
        {
            auto queue = ToKernelWorkQueue();

            if ((this->uAtomicCounter == state->stackState.uStackCallDepth) &&
                this->IsDepleted())
            {
                return false;
            }
        }

        //
        for (auto itr = state->pendingWorkItems.begin(); itr != state->pendingWorkItems.end(); )
        {
            if (state->thread.pThread->Exiting())
            {
                break;
            }

            // Dispatch
            auto oops = itr->second;

            // Remove from our local job queue
            itr = state->pendingWorkItems.erase(itr);

            state->stackState.uStackCallDepth++;

            //SysBenchmark(fmt::format("RunAsync: {}", block));
            // Dispatch
            oops->RunAsync();
            uCount++;

            // Atomically decrement global task counter
            runningTasks = AuAtomicSub(&this->uAtomicCounter, 1u);

            state->stackState.uStackCallDepth--;

            if (uStartCookie != state->stackState.uStackCookie)
            {
                uStartCookie = state->stackState.uStackCookie;
                itr = state->pendingWorkItems.begin();
            }
        }

        // Return popped work back to the groups work pool when our -pump loops were preempted 
        if (state->pendingWorkItems.size())
        {
            AU_LOCK_GUARD(state->sync.cvWorkMutex);

            for (const auto &item : state->pendingWorkItems)
            {
                group->workQueue.AddWorkEntry(state.get(), item);
            }

            state->pendingWorkItems.clear();
            state->sync.cvVariable->Broadcast();
            state->sync.eventLs->Set();
        }

        // Account for 
        //            while (AuAsync.GetCurrentPool()->runForever());
        // in the top most task
        if (InRunnerMode())
        {
            auto queue = ToKernelWorkQueue();

            if ((runningTasks == 0) &&
                (this->uAtomicCounter == 0) &&
                this->IsDepleted())
            {
                Shutdown();
            }
        }
        
        return true;
    }

    // While much of this subsystem needs good rewrite, under no circumstance should the shutdown process be "simpified" or "cleaned up"
    // This is our expected behaviour. Any changes will likely introduce hard to catch bugs across various softwares and exit conditions.
    void ThreadPool::Shutdown()
    {
        auto trySelfPid = AuAsync::GetCurrentWorkerPId();

        // Update shutting down flag
        // Specify the root-level shutdown flag for 'ok, u can work, but you're shutting down soon [microseconds, probably]'
        {
            if (AuAtomicTestAndSet(&this->shuttingdown_, 0) != 0)
            {
                return;
            }
        }

        auto pLocalRunner = this->GetThreadStateNoWarn();

        AuList<WorkerId_t> toBarrier;

        // wait for regular prio work to complete
        {
            for (auto pGroup : this->threadGroups_)
            {
                if (!pGroup)
                {
                    continue;
                }

                AU_LOCK_GUARD(pGroup->workersMutex);
                for (auto &[id, worker] : pGroup->workers)
                {
                    if (trySelfPid == worker->thread.id)
                    {
                        continue;
                    }

                    toBarrier.push_back(worker->thread.id);
                }
            }

            for (const auto &id : toBarrier)
            {
                if (trySelfPid == id)
                {
                    continue;
                }

                this->Barrier(id, 0, false, false /* no reject*/); // absolute safest point in shutdown; sync to already submitted work 
            }
        }

        // increment abort cookies
        {
            for (const auto &id : toBarrier)
            {
                if (trySelfPid == id)
                {
                    continue;
                }

                AuAtomicAdd(&this->uAtomicShutdownCookie, 1u);
            }
        }

        // set shutdown flags
        {
            AuAtomicTestAndSet(&this->shuttingdown_, 1);
        }

        // Finally set the shutdown flag on all of our thread contexts
        // then release them from the runners/workers list
        // then release all group contexts
        AuList<AuThreads::ThreadShared_t> threads;
        AuList<AuSPtr<ThreadState>> states;
        {
            AU_LOCK_GUARD(this->pRWReadView);

            for (auto pGroup : this->threadGroups_)
            {
                if (!pGroup)
                {
                    continue;
                }

                for (auto &[id, pState] : pGroup->workers)
                {
                    // main loop:
                    if (pState)
                    {
                        states.push_back(pState);
                        pState->shuttingdown = true;
                    }
                    else
                    {
                        pState->shuttingdown = true;
                    }

                    // thread object:
                    if (pState->thread.bOwnsThread)
                    {
                        pState->thread.pThread->SendExitSignal();
                        threads.push_back(pState->thread.pThread);
                    }

                    // unrefreeze signals:
                    auto &event = pState->running;
                    if (event)
                    {
                        event->Set();
                    }
                }
            }
        }

        // Break all condvar loops, just in case
        for (const auto &pState : states)
        {
            pState->sync.SetEvent();
        }

        // Final sync to exit
        {
            for (const auto &id : toBarrier)
            {
                if (trySelfPid == id)
                {
                    continue;
                }

                auto handle = this->GetThreadHandle(id);
                if (handle)
                {
                    handle->shutdown.bDropSubmissions = false;
                    handle->isDeadEvent->LockMS(250);
                }
            }
        }

        // Sync to shutdown threads to prevent a race condition whereby the async subsystem shuts down before the threads
        auto pSelf = AuThreads::GetThread();
        for (const auto &thread : threads)
        {
            if (thread.get() != pSelf)
            {
                thread->Exit();
            }
        }

        // Is dead flag
        this->shutdownEvent_->Set();

        //
        if (pLocalRunner)
        {
            pLocalRunner->shutdown.bIsKillerThread = true;
        }

        // Notify observing threads of our work exhaustion
        for (const auto &wOther : this->listWeakDepsParents_)
        {
            if (auto pThat = AuTryLockMemoryType(wOther))
            {
                if (pThat->InRunnerMode())
                {
                    continue;
                }

                if (!pThat->IsSelfDepleted())
                {
                    continue;
                }

                if (pThat->uAtomicCounter)
                {
                    continue;
                }

                pThat->Shutdown();
            }
        }
    }

    bool ThreadPool::Exiting()
    {
        return this->shuttingdown_ ||
               GetThreadState()->exiting;
    }
    
    AuUInt32 ThreadPool::PollAndCount(bool bStrict)
    {
        AuUInt32 uCount {};
        auto bRanAtLeastOne = this->InternalRunOne(this->GetThreadStateNoWarn(), false, uCount);
        return uCount ? uCount : (bStrict ? bRanAtLeastOne : 0);
    }
    
    AuUInt32 ThreadPool::RunAllPending()
    {
        AuUInt32 uCount {};
        bool ranAtLeastOne {};

        do
        {
            uCount = 0;
            ranAtLeastOne |= this->InternalRunOne(this->GetThreadStateNoWarn(), false, uCount);
        }
        while (uCount);

        return uCount ? uCount : false;
    }

    AuSPtr<IWorkItem> ThreadPool::NewWorkItem(const WorkerId_t &worker,
                                              const AuSPtr<IWorkItemHandler> &task)
    {
        // Error pass-through
        if (!task)
        {
            return {};
        }

        return AuMakeShared<WorkItem>(this, WorkerPId_t { this->SharedFromThis(), worker }, task);
    }
    
    AuSPtr<IWorkItem> ThreadPool::NewWorkFunction(const WorkerId_t &worker,
                                                  AuVoidFunc callback)

    {
        SysAssert(callback);
        return AuMakeShared<AsyncFuncWorker>(this, WorkerPId_t { this->SharedFromThis(), worker }, AuMove(callback));
    }

    AuSPtr<IWorkItem> ThreadPool::NewFence()
    {
        return AuMakeShared<WorkItem>(this, AuAsync::GetCurrentWorkerPId(), AuSPtr<IWorkItemHandler>{});
    }

    AuThreads::ThreadShared_t ThreadPool::ResolveHandle(WorkerId_t id)
    {
        auto pState = GetThreadHandle(id);
        if (!pState)
        {
            return {};
        }

        return pState->thread.pThread;
    }
    
    AuBST<ThreadGroup_t, AuList<ThreadId_t>> ThreadPool::GetThreads()
    {
        AuBST<ThreadGroup_t, AuList<ThreadId_t>> ret;

        for (auto pGroup : this->threadGroups_)
        {
            AuList<ThreadId_t> workers;

            if (!pGroup)
            {
                continue;
            }

            AU_LOCK_GUARD(pGroup->workersMutex);
            AuTryReserve(workers, pGroup->workers.size());

            for (const auto &thread : pGroup->workers)
            {
                workers.push_back(thread.second->thread.id.second);
            }

            ret[pGroup->group] = workers;
        }

        return ret;
    }
    
    WorkerId_t ThreadPool::GetCurrentThread()
    {
        return tlsWorkerId;
    }

    AuSPtr<AuIO::IIOProcessor> ThreadPool::GetIOProcessor(WorkerId_t pid)
    {
        if (auto pState = this->GetThreadHandle(pid))
        {
            return pState->singletons.GetIOProcessor({ this->SharedFromThis(), pid });
        }

        return {};
    }

    AuSPtr<AuIO::Net::INetInterface> ThreadPool::GetIONetInterface(WorkerId_t pid)
    {
        if (auto pState = this->GetThreadHandle(pid))
        {
            return pState->singletons.GetIONetInterface({ this->SharedFromThis(), pid });
        }

        return {};
    }

    AuSPtr<AuIO::Net::INetWorker> ThreadPool::GetIONetWorker(WorkerId_t pid)
    {
        if (auto pState = this->GetThreadHandle(pid))
        {
            return pState->singletons.GetIONetWorker({ this->SharedFromThis(), pid });
        }

        return {};
    }

    AuSPtr<IO::IIOProcessor>       ThreadPool::GetSelfIOProcessor()
    {
        auto pid = GetCurrentWorkerPId();
        if (pid)
        {
            return pid.GetPool()->GetIOProcessor(pid);
        }
        else
        {
            return {};
        }
    }

    AuSPtr<IO::Net::INetInterface> ThreadPool::GetSelfIONetInterface()
    {
        auto pid = GetCurrentWorkerPId();
        if (pid)
        {
            return pid.GetPool()->GetIONetInterface(pid);
        }
        else
        {
            return {};
        }
    }

    AuSPtr<IO::Net::INetWorker>    ThreadPool::GetSelfIONetWorker()
    {
        auto pid = GetCurrentWorkerPId();
        if (pid)
        {
            return pid.GetPool()->GetIONetWorker(pid);
        }
        else
        {
            return {};
        }
    }
  
    bool ThreadPool::Sync(WorkerId_t workerId, AuUInt32 timeoutMs, bool requireSignal)
    {
        AU_LOCK_GUARD(this->pRWReadView);
        
        auto group = GetGroup(workerId.first);
        auto currentWorkerId = GetCurrentThread().second;

        if (workerId.second == Async::kThreadIdAny)
        {
            for (auto &jobWorker : group->workers)
            {
                if (!Barrier(jobWorker.second->thread.id, timeoutMs, requireSignal && jobWorker.second->thread.id.second != currentWorkerId, false)) // BAD!, should subtract time elapsed, clamp to, i dunno, 5ms min?
                {
                    return false;
                }
            }
        }
        else
        {
            return Barrier(workerId, timeoutMs, requireSignal && workerId.second != currentWorkerId, false);
        }

        return true;
    }
    
    void ThreadPool::Signal(WorkerId_t workerId)
    {
        auto group = GetGroup(workerId.first);
        if (workerId.second == Async::kThreadIdAny)
        {
            AU_LOCK_GUARD(group->workersMutex);
            for (auto &jobWorker : group->workers)
            {
                jobWorker.second->running->Set();
            }
        }
        else
        {
            GetThreadHandle(workerId)->running->Set();
        }
    }

    AuSPtr<AuLoop::ILoopSource> ThreadPool::WorkerToLoopSource(WorkerId_t workerId)
    {
        auto a = GetThreadHandle(workerId);
        if (!a)
        {
            return {};
        }

        return a->sync.eventLs;
    }
    
    void ThreadPool::SyncAllSafe()
    {
        AU_LOCK_GUARD(this->pRWReadView);

        for (auto pGroup : this->threadGroups_)
        {
            if (!pGroup)
            {
                continue;
            }

            for (auto &jobWorker : pGroup->workers)
            {
                SysAssert(Barrier(jobWorker.second->thread.id, 0, false, false));
            }
        }
    }
    
    void ThreadPool::AddFeature(WorkerId_t id,
                                AuSPtr<AuThreads::IThreadFeature> pFeature,
                                bool bNonBlock)
    {
        auto pWorkItem = DispatchOn({ this->SharedFromThis(), id }, [=]()
        {
            auto pState = GetThreadState();
            {
                AU_LOCK_GUARD(pState->tlsFeatures.mutex);
                pState->tlsFeatures.features.push_back(pFeature);
            }
            pFeature->Init();
        });

        if (!bNonBlock)
        {
            pWorkItem->BlockUntilComplete();
        }
    }
    
    void ThreadPool::AssertInThreadGroup(ThreadGroup_t group)
    {
        SysAssert(static_cast<WorkerId_t>(tlsWorkerId).first == group);
    }

    void ThreadPool::AssertWorker(WorkerId_t id)
    {
        SysAssert(static_cast<WorkerId_t>(tlsWorkerId) == id);
    }
    
    AuSPtr<AuLoop::ILoopQueue> ThreadPool::ToKernelWorkQueue()
    {
        return this->GetThreadState()->asyncLoop;
    }

    AuSPtr<AuLoop::ILoopQueue> ThreadPool::ToKernelWorkQueue(WorkerId_t workerId)
    {
        auto worker = this->GetThreadHandle(workerId);
        if (!worker)
        {
            SysPushErrorGeneric("Couldn't find requested worker");
            return {};
        }
        return worker->asyncLoop;
    }

    bool ThreadPool::IsSelfDepleted()
    {
        auto queue = ToKernelWorkQueue();
        return (!queue || queue->GetSourceCount() <= 1 + this->uAtomicIOProcessorsWorthlessSources + this->uAtomicIOProcessors);
    }

    bool ThreadPool::IsDepleted()
    {
        if (!IsSelfDepleted())
        {
            return false;
        }

        for (const auto &wOther : this->listWeakDeps_)
        {
            if (auto pThat = AuTryLockMemoryType(wOther))
            {
                if (!pThat->IsSelfDepleted())
                {
                    return false;
                }
            
                if (pThat->uAtomicCounter)
                {
                    return false;
                }
            }
        }

        return true;
    }

    void ThreadPool::AddDependency(AuSPtr<IThreadPool> pPool)
    {
        if (!pPool)
        {
            return;
        }

        auto pOther = AuStaticCast<ThreadPool>(pPool);
        this->listWeakDeps_.push_back(pOther);
        pOther->listWeakDepsParents_.push_back(AuSharedFromThis());
    }

    AuSPtr<AuThreading::IWaitable> ThreadPool::GetShutdownEvent()
    {
        return AuSPtr<AuThreading::IWaitable>(AuSharedFromThis(), this->shutdownEvent_.AsPointer());
    }

    // Unimplemented fiber hooks, 'twas used for science. no longer in use
    
    int ThreadPool::CtxPollPush()
    {
        // TOOD (Reece): implement a context switching library  
        // Refer to the old implementation of this on pastebin
        return 0;
    }

    void ThreadPool::CtxPollReturn(const AuSPtr<ThreadState> &state, int status, bool hitTask)
    {
    }

    bool ThreadPool::CtxYield()
    {
        bool ranAtLeastOne = false;

        // !!!

        auto pA = this->GetThreadStateNoWarn();

        if (this->shuttingdown_ & 2) // fast 
        {
            if (pA->shutdown.bDropSubmissions)
            {
                return false;
            }
        }

    #if 0
        return this->InternalRunOne(false, uCount);
    #else
        AuUInt32 uCount {};
        do
        {
            uCount = 0;
            ranAtLeastOne |= this->InternalRunOne(pA, false, uCount);
        }
        while (uCount);

        return uCount || ranAtLeastOne;
    #endif
    }

    //

    void ThreadPool::IncrementAbortFenceOnPool()
    {
        AuAtomicAdd(&this->uAtomicShutdownCookie, 1u);
    }

    void ThreadPool::IncrementAbortFenceOnWorker(WorkerId_t workerId)
    {
        if (auto pState = this->GetThreadHandle(workerId))
        {
            AuAtomicAdd(&pState->shutdown.uShutdownFence, 1u);
        }
    }

    AuUInt64 ThreadPool::QueryAbortFence(AuOptional<WorkerId_t> optWorkerId)
    {
        if (auto pState = this->GetThreadHandle(optWorkerId.value_or(GetCurrentWorkerPId())))
        {
            return (AuUInt64(pState->shutdown.uShutdownFence) << 32ull) | AuUInt64(this->uAtomicShutdownCookie);
        }
        else
        {
            return this->uAtomicShutdownCookie;
        }
    }

    bool ThreadPool::QueryShouldAbort(AuOptional<WorkerId_t> optWorkerId, AuUInt64 uFenceMagic)

    {
        auto uSelfCookie = AuBitsToLower(uFenceMagic);
        if (uSelfCookie != AuAtomicLoad(&this->uAtomicShutdownCookie))
        {
            return true;
        }

        auto uThreadCookie = AuBitsToHigher(uFenceMagic);
        if (!uThreadCookie)
        {
            return false;
        }

        if (auto pState = this->GetThreadHandle(optWorkerId.value_or(GetCurrentWorkerPId())))
        {
            return uThreadCookie != pState->shutdown.uShutdownFence;
        }
        else
        {
            return false;
        }
    }


    // internal api
    
    bool ThreadPool::Spawn(WorkerId_t workerId, bool create)
    {
        AU_LOCK_GUARD(rwlock_->AsWritable());

        if (create)
        {
            tlsCurrentThreadPool = AuSharedFromThis();
        }

        AuSPtr<GroupState> pGroup;

        // Try fetch or allocate group
        {
            if (!(pGroup = threadGroups_[workerId.first]))
            {
                pGroup = AuMakeShared<GroupState>();

                if (!pGroup->Init())
                {
                    SysPushErrorMemory("Not enough memory to intiialize a new group state");
                    return false;
                }

                this->threadGroups_[workerId.first] = pGroup;
            }
        }

        // Assert worker does not already exist
        {
            AuSPtr<ThreadState>* ret;

            if (AuTryFind(pGroup->workers, workerId.second, ret))
            {
                SysPushErrorGeneric("Thread ID already exists");
                return false;
            }
        }

        auto pThreadState = pGroup->CreateWorker(workerId, create);
        if (!pThreadState)
        {
            return {};
        }

        if (!create)
        {
            pThreadState->thread.pThread= AuThreads::ThreadShared(AuThreads::ThreadInfo(
                AuMakeShared<AuThreads::IThreadVectorsFunctional>(AuThreads::IThreadVectorsFunctional::OnEntry_t(std::bind(&ThreadPool::Entrypoint, this, workerId)),
                                                                  AuThreads::IThreadVectorsFunctional::OnExit_t{}),
                gRuntimeConfig.async.threadPoolDefaultStackSize
            ));

            if (!pThreadState->thread.pThread)
            {
                return {};
            }

            pThreadState->thread.pThread->Run();
        }
        else
        {
            pThreadState->thread.pThread = AuSPtr<AuThreads::IAuroraThread>(AuThreads::GetThread(), [](AuThreads::IAuroraThread *){});
            
            // TODO: this is just a hack
            // we should implement this properly
            pThreadState->thread.pThread->AddLastHopeTlsHook(AuMakeShared<AuThreads::IThreadFeatureFunctional>([]() -> void
            {

            }, []() -> void
            {
                auto pid = GetCurrentWorkerPId();
                if (pid)
                {
                    GetWorkerInternal(pid.GetPool())->ThisExiting();
                }
            }));

            tlsCurrentThreadPool = AuWeakFromThis();
            tlsWorkerId = WorkerPId_t(AuSharedFromThis(), workerId);
        }
        
        pGroup->AddWorker(workerId.second, pThreadState);
        return true;
    }

    // private api

    AU_NOINLINE bool ThreadPool::Barrier(WorkerId_t workerId, AuUInt32 ms, bool requireSignal, bool drop)
    {
        auto self = GetThreadState();
        if (!self)
        {
            return {};
        }

        auto &semaphore = self->syncSema;
        auto unsafeSemaphore = semaphore.AsPointer();
        bool failed {};

        auto work = AuMakeShared<AsyncFuncRunnable>(
            [=]()
            {
                auto state = GetThreadState();

                if (drop)
                {
                    state->shutdown.bDropSubmissions = true;
                }

                if (requireSignal)
                {
                    state->running->Reset();
                }

                unsafeSemaphore->Unlock(1);

                if (requireSignal)
                {
                    state->running->Lock();
                }
            },
            [&]()
            {
                unsafeSemaphore->Unlock(1);
                failed = true;
            }
        );

        if (!work)
        {
            return false;
        }

        Run(workerId, work);

        return WaitFor(workerId, AuUnsafeRaiiToShared(semaphore.AsPointer()), ms) && !failed;
    }

    void ThreadPool::Entrypoint(WorkerId_t id)
    {
        {
            AU_LOCK_GUARD(this->pRWReadView);
        }

        tlsCurrentThreadPool  = AuWeakFromThis();
        tlsWorkerId   = WorkerPId_t(AuSharedFromThis(), id);

        auto job      = GetThreadState();

        Run();

        if (id != WorkerId_t {0, 0})
        {
            AU_LOCK_GUARD(this->pRWReadView);

            if (!this->shuttingdown_ && !job->shutdown.bDropSubmissions)
            {
                // Pump and barrier + reject all after atomically
                Barrier(id, 0, false, true);
            }
        }

        ThisExiting();
        
        if (id == WorkerId_t {0, 0})
        {
            CleanWorkerPoolReservedZeroFree();
        }
    }

    void ThreadPool::EarlyExitTick()
    {
        auto jobWorker = GetThreadState();
        auto state = jobWorker->parent.lock();
        if (!jobWorker)
        {
            SysPushErrorUninitialized("Not an async thread");
            return;
        }

        if ((this->shuttingdown_ & 2) != 2)
        {
            return;
        }

        state->SignalAll();

        {
            if (AuExchange(jobWorker->bAlreadyDoingExitTick, true))
            {
                return;
            }

            AuUInt32 uCount {};
            do
            {
                uCount = 0;
                this->PollInternal(jobWorker, false, uCount);
            }
            while (uCount);
        }


        AuList<AuSPtr<AuThreads::IThreadFeature>> features;
        {
            AU_LOCK_GUARD(jobWorker->tlsFeatures.mutex);
            features = AuExchange(jobWorker->tlsFeatures.features, {});
        }

        {
            for (const auto &thread : features)
            {
                try
                {
                    thread->Cleanup();
                }
                catch (...)
                {
                    SysPushErrorCatch("Couldn't clean up thread feature!");
                }
            }

            jobWorker->isDeadEvent->Set();

            jobWorker->bAlreadyDoingExitTick = false;
            jobWorker->shutdown.bBreakMainLoop = true;
        }
    }
    
    void ThreadPool::ThisExiting()
    {
        auto id    = GetCurrentThread();
        auto state = GetGroup(id.first);

        auto pLocalState = state->GetThreadByIndex(id.second);

        AuList<AuSPtr<AuThreads::IThreadFeature>> features;
        {
            AU_LOCK_GUARD(this->pRWReadView);

            pLocalState->isDeadEvent->Set();

            CleanUpWorker(id);

            TerminateSceduledTasks(this, id);

            pLocalState->syncSema->Unlock(10); // prevent ::Barrier dead-locks 

            {
                AU_LOCK_GUARD(pLocalState->externalFencesLock);
                pLocalState->exitingflag2 = true;

                for (const auto &pIWaitable : pLocalState->externalFences)
                {
                    pIWaitable->Unlock();
                }

                pLocalState->externalFences.clear();
            }

            {
                AU_LOCK_GUARD(pLocalState->tlsFeatures.mutex);
                features = AuExchange(pLocalState->tlsFeatures.features, {});
            }
        }

        {
            for (const auto &thread : features)
            {
                try
                {
                    thread->Cleanup();
                }
                catch (...)
                {
                    SysPushErrorConcurrentRejected("Couldn't clean up thread feature!");
                }
            }

            features.clear();
        }

        {
            state->Decommit(id.second);
        }
    }

    AuSPtr<GroupState>  ThreadPool::GetGroup(ThreadGroup_t type)
    {
        return this->threadGroups_[type];
    }

    AuSPtr<ThreadState> ThreadPool::GetThreadState()
    {
        auto thread = tlsCurrentThreadPool.lock();
        if (!thread)
        {
            return {};
        }

    #if defined(AU_CFG_ID_INTERNAL) || defined(AU_CFG_ID_DEBUG)
        if (thread.get() != this)
        {
            SysPushErrorGeneric("wrong thread");
            return {};
        }
    #endif 

        auto worker = *tlsWorkerId;
        auto state = GetGroup(worker.first);
        if (!state)
        {
            return {};
        }

        return state->GetThreadByIndex(worker.second);
    }

    AuSPtr<ThreadState> ThreadPool::GetThreadStateNoWarn()
    {
        auto thread = tlsCurrentThreadPool.lock();
        if (!thread)
        {
            return {};
        }

        if (thread.get() != this)
        {
            return {};
        }

        auto worker = *tlsWorkerId;

        auto state = GetGroup(worker.first);
        if (!state)
        {
            return {};
        }

        return state->GetThreadByIndex(worker.second);
    }

    AuSPtr<ThreadState> ThreadPool::GetThreadHandle(WorkerId_t id)
    {
        auto group = GetGroup(id.first);
        if (!group)
        {
            return {};
        }

        return group->GetThreadByIndex(id.second);
    }

    AuList<AuSPtr<ThreadState>> ThreadPool::GetThreadHandles(WorkerId_t id)
    {
        auto group = GetGroup(id.first);
        if (!group)
        {
            return {};
        }
       
        AuList<AuSPtr<ThreadState>> ret;
        if (id.second != Async::kThreadIdAny)
        {
            if (auto pPtr = group->GetThreadByIndex(id.second))
            {
                ret.push_back(pPtr);
            }
        }
        else
        {
            AU_LOCK_GUARD(group->workersMutex);
            for (const auto &[key, value] : group->workers)
            {
                ret.push_back(value);
            }
        }
    
        return ret;
    }

    AUKN_SYM AuSPtr<IThreadPool> NewThreadPool()
    {
        // apps that don't require async shouldn't be burdened with the overhead of this litl spiner
        StartSched();
        return AuMakeShared<ThreadPool>();
    }

}