95 lines
2.6 KiB
C++
95 lines
2.6 KiB
C++
/***
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Copyright (C) 2021 J Reece Wilson (a/k/a "Reece"). All rights reserved.
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File: AuConditionVariable.Generic.cpp
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Date: 2021-6-14
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Author: Reece
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***/
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#include <Source/RuntimeInternal.hpp>
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#include <Source/Threading/AuWaitFor.hpp>
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#include "AuConditionVariable.Generic.hpp"
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#if defined(_AURUNTIME_GENERICCV)
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namespace Aurora::Threading::Primitives
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{
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ConditionVariableImpl::ConditionVariableImpl(const AuSPtr<IConditionMutex> &mutex) : mutex_(AuDynamicCast<ConditionMutexImpl>(mutex))
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{
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}
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AuSPtr<IConditionMutex> ConditionVariableImpl::GetMutex()
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{
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return mutex_;
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}
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bool ConditionVariableImpl::WaitForSignal(AuUInt32 timeout)
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{
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// yield then wake up spuriously - this is should be illegal, but works well enough as a place holder
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mutex_->Unlock();
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for (int i = 0; i < 20; i++)
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{
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YieldToOtherThread();
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}
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mutex_->Lock();
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/**
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TODO: A more technically competent solution may be more sophisticated than anything proposed here,
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but the following seems good enough.
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It's same thing without the spurious wake ups and hopefully scalable timeout-relative yielding
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wait ->
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waiting_++
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WaitFor([]() {
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auto old = signals_.load(std::memory_order_relaxed);
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return old != 0 && signals_.compare_exchange_strong(old, old - 1);
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})
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*/
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return true;
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}
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void ConditionVariableImpl::Signal()
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{
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signals_++;
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waiting_--;
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}
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void ConditionVariableImpl::Broadcast()
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{
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auto initwaiting = waiting_.load(std::memory_order_relaxed);
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if (initwaiting < 0) return;
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signals_ += initwaiting;
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#if 0
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auto old = initwaiting;
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if (!old) return;
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while (!(waiting_.compare_exchange_strong(old, old - initwaiting)))
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{
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old = waiting_.load(std::memory_order_relaxed);
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if (!old) return;
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}
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#else
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waiting_ -= initwaiting;
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// is it possible to go negative on waiters? yes!
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// is it a big deal? well, no actually
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// the only way this can happen is if we have above 0 signals and no threads waiting
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// it should sort itself out
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#endif
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}
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AUKN_SYM IConditionVariable *ConditionVariableNew(const AuSPtr<IConditionMutex> &mutex)
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{
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return _new ConditionVariableImpl(mutex);
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}
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AUKN_SYM void ConditionVariableRelease(IConditionVariable *mutex)
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{
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AuSafeDelete<ConditionVariableImpl *>(mutex);
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}
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}
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#endif |