Source/JavaScriptCore/heap/SynchronousStopTheWorldMutatorScheduler.h

/*
 * Copyright (C) 2017 Apple Inc. All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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#pragma once

#include "MutatorScheduler.h"

namespace JSC {

// The JSC concurrent GC relies on stopping the world to stay ahead of the retreating wavefront.
// It so happens that the same API can be reused to implement a non-concurrent GC mode, which we
// use on platforms that don't support the GC's atomicity protocols. That means anything other
// than X86-64 and ARM64. This scheduler is a drop-in replacement for the concurrent GC's
// SpaceTimeMutatorScheduler. It tells the GC to never resume the world once the GC cycle begins.

class SynchronousStopTheWorldMutatorScheduler final : public MutatorScheduler {
public:
    SynchronousStopTheWorldMutatorScheduler();
    ~SynchronousStopTheWorldMutatorScheduler() final;
    
    State state() const final;
    
    void beginCollection() final;
    
    MonotonicTime timeToStop() final;
    MonotonicTime timeToResume() final;
    
    void endCollection() final;

private:
    State m_state { Normal };
};

} // namespace JSC