42 lines
1.2 KiB
C++
42 lines
1.2 KiB
C++
// Copyright (c) Wojciech Figat. All rights reserved.
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#include "ConcurrentSystemLocker.h"
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#include "Engine/Platform/Platform.h"
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ConcurrentSystemLocker::ConcurrentSystemLocker()
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{
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_counters[0] = _counters[1] = 0;
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}
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void ConcurrentSystemLocker::Begin(bool write)
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{
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volatile int64* thisCounter = &_counters[write];
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volatile int64* otherCounter = &_counters[!write];
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RETRY:
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// Check if we can enter (cannot read while someone else is writing and vice versa)
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if (Platform::AtomicRead(otherCounter) != 0)
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{
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// Someone else is doing opposite operation so wait for it's end
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// TODO: use ConditionVariable+CriticalSection to prevent active-waiting
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Platform::Sleep(0);
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goto RETRY;
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}
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// Mark that we entered this section
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Platform::InterlockedIncrement(thisCounter);
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// Double-check if we're safe to go
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if (Platform::InterlockedCompareExchange(otherCounter, 0, 0))
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{
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// Someone else is doing opposite operation while this thread was doing counter increment so retry
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Platform::InterlockedDecrement(thisCounter);
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goto RETRY;
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}
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}
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void ConcurrentSystemLocker::End(bool write)
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{
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// Mark that we left this section
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Platform::InterlockedDecrement(&_counters[write]);
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}
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