84 lines
3.7 KiB
C++
84 lines
3.7 KiB
C++
/***
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Copyright (C) 2021 J Reece Wilson (a/k/a "Reece"). All rights reserved.
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File: ConditionVariable.Win32.hpp
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Date: 2021-6-12
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Author: Reece
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***/
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#pragma once
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#if !defined(_AURUNTIME_GENERICCV)
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#include "AuConditionMutex.NT.hpp"
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namespace Aurora::Threading::Primitives
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{
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struct ConditionVariableImpl final : IConditionVariable
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{
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ConditionVariableImpl(const AuSPtr<IConditionMutex> &mutex);
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auline AuSPtr<IConditionMutex> GetMutex() override;
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auline bool WaitForSignal(AuUInt32 timeout) override;
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/*auline*/bool WaitForSignalNsEx(const std::shared_ptr<Win32ConditionMutex> &pMutex, AuUInt64 timeout);
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/*auline*/bool WaitForSignalNS(AuUInt64 qwTimeout) override;
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auline void Signal() override;
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auline void Broadcast() override;
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auline bool CheckOut();
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private:
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#if defined(AURORA_FORCE_SRW_LOCKS)
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CONDITION_VARIABLE winCond_;
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#else
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AuUInt32 wlist {};
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AuUInt32 signalCount {};
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#endif
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std::shared_ptr<Win32ConditionMutex> mutex_;
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};
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struct CondVarDummy : IConditionVariable
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{
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private:
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#if defined(AURORA_FORCE_SRW_LOCKS)
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CONDITION_VARIABLE winCond_;
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#else
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AuUInt32 wlist {};
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AuUInt32 signalCount {};
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#endif
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};
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static const auto kSizeOfDummyCondVar = sizeof(CondVarDummy);
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static const auto kBoolRequiredLateSet = true;
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// Future (Reece): I got future plans
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static const auto kShiftCountByBits = 8u;
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// ...otherwise
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// assume undefined behaviour past:
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// * bit zero is used for atomic bit test and yield loops
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// ( keyed events are an optimization mechanism for Windows XPs spinloop i had accidentally recreated in xenus. )
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// ( originally, nt yielding sucked with the most barebones spinlock being dumb a hypervisor-unaware, smt-aware, spinner. )
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// ( keyed events would then go in these spinners to serve as an early futex as early back as the year 2000 (?). )
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// ( that does, in fact, mean the free-toddlers crying about how 'windows stole muh kernels totally originally idea' is entirely wrong at each sub-point. )
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// ( though, keyed didn't see much use until Windows Vistas synch primitives were built on top of them. )
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// ( infamously missing 100ths scale nanosecond yimeouts and an inablity to lock with a timeout. )
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// ( raymond chen once claimed they didnt make it to xp because they werent fast enough )
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// ( raymond chen once claimed a "con" of keyedevents were that they were linear )
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// ( problem is, as far as i can tell, they didnt really change. whats worse, WakeOnAddress (windows 8+)
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// ( ...inherits the issue of not having relative/abs nanosecond scale timeouts AND the issue the primitives sucking. )
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// ( WakeOnAddress is nothing more than keyed events 2.0 - but with userland list keeping. )
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// ( scratch the concept of how i implement WakeOnAddress with lists, how older nts waited with lists under lock, )
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// ( they use hashmaps with "le meme lockless" interactions which are surly less expensive than reusing tls allocations ?! )
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// ( whether or not its even faster is still up for debate. its just easier to use. )
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// * bit one might be used under some niche versions of windows
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// (hearsay paranoia)
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// i actually have zero reason to believe windows ever implemented lock-awareness into the kernel
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// i think it might be fine to skip the whole bit zero thing, but still, im going to say keep the min=2
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// worst case scenario, we end up using these bits.
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// ....
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// =8 is future proof
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// =2 is recommended
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// =0 would require a bit of a require. i think this is how other people use keyed events nowadays
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}
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#endif |