AuroraRuntime/Source/Threading/Primitives/AuMutex.Unix.cpp

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

    File: AuMutex.Unix.cpp
    Date: 2021-6-12
    Author: Reece
***/
#include <Source/RuntimeInternal.hpp>
#include "AuMutex.Generic.hpp"
#include "SMPYield.hpp"

#if !defined(_AURUNTIME_GENERIC_MUTEX) && !defined(AURORA_IS_LINUX_DERIVED)
#include <Source/Time/Time.hpp>
        
namespace Aurora::Threading::Primitives
{
    Mutex::Mutex()
    {
        pthread_condattr_t attr;
        
        ::pthread_condattr_init(&attr);
        ::pthread_condattr_setclock(&attr, CLOCK_MONOTONIC);

        SysAssert(::pthread_cond_init(&this->pthreadCv_, &attr) == 0, "couldn't initialize mutex/CV");
    }
    
    Mutex::~Mutex()
    {
        ::pthread_cond_destroy(&this->pthreadCv_);
    }

    bool Mutex::HasOSHandle(AuMach &mach)
    {
        return false;
    }
    
    bool Mutex::HasLockImplementation()
    {
        return true;
    }
   
    bool Mutex::TryLock()
    {
        // Assume heavyweight pthread_cond_timedwait yield is followed by an instant hit, for now
        auto old = this->value_;
        return (old == 0 && AuAtomicCompareExchange(&this->value_, 1, old) == old);
    }

    bool Mutex::Lock(AuUInt64 uTimeout)
    {
        return LockNS(AuMSToNS<AuUInt64>(uTimeout));
    }

    bool Mutex::LockNS(AuUInt64 uTimeout)
    {
        if (DoTryIf([=]()
        {
            auto old = this->value_;
            return (old == 0 && AuAtomicCompareExchange(&this->value_, 1, old) == old);
        }))
        {
            return true;
        }

        AuUInt64 uStart = AuTime::SteadyClockNS();
        AuUInt64 uEnd = uStart + uTimeout;

        AU_LOCK_GUARD(this->mutex_);
        auto mutex = reinterpret_cast<pthread_mutex_t*>(this->mutex_.GetOSHandle());

        struct timespec tspec;
        if (uTimeout != 0)
        {
            Time::auabsns2ts(&tspec, uEnd);
        }

        int ret {};
        while (!this->TryLock())
        {
            if (uTimeout != 0)
            {
                uStart = Time::SteadyClockNS();
                if (uStart >= uEnd)
                {
                    return false;
                }

                do
                {
                    ret = ::pthread_cond_timedwait(&this->pthreadCv_, mutex, &tspec);
                }
                while (ret == EINTR);
            }
            else
            {
                bool bStatus {};

                do
                {
                    if ((ret = ::pthread_cond_wait(&this->pthreadCv_, mutex)) == 0)
                    {
                        bStatus = true;
                        break;
                    }
                }
                while (ret == EINTR);

                RUNTIME_ASSERT_SHUTDOWN_SAFE(bStatus, "Mutex wait failed: {}", ret)
            }
        }

        return true;
    }
    
    void Mutex::Lock()
    {
        auto status = Lock(0);
        SysAssert(status, "Couldn't lock mutex");
    }
    
    void Mutex::Unlock()
    {
        {
            AU_LOCK_GUARD(this->mutex_);
            this->value_ = 0;
        }
        auto ret = ::pthread_cond_signal(&this->pthreadCv_);
        SysAssert(ret == 0, "Couldn't wake any mutex waiter");
    }
    
    AUKN_SYM IWaitable *MutexNew()
    {
        return _new Mutex();
    }

    AUKN_SYM void MutexRelease(IWaitable *pMutex)
    {
        AuSafeDelete<Mutex *>(pMutex);
    }
}
#endif