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https://github.com/darlinghq/darling-JavaScriptCore.git
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59 lines
2.3 KiB
C
59 lines
2.3 KiB
C
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/*
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* Copyright (C) 2016 Apple Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
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* THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include "Heap.h"
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namespace JSC {
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// Almost all of the VM's code runs with "heap access". This means that the GC thread believes that
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// the VM is messing with the heap in a way that would be unsafe for certain phases of the collector,
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// like the weak reference fixpoint, stack scanning, and changing barrier modes. However, many long
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// running operations inside the VM don't require heap access. For example, memcpying a typed array
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// if a reference to it is on the stack is totally fine without heap access. Blocking on a futex is
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// also fine without heap access. Releasing heap access for long-running code (in the case of futex
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// wait, possibly infinitely long-running) ensures that the GC can finish a collection cycle while
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// you are waiting.
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class ReleaseHeapAccessScope {
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public:
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ReleaseHeapAccessScope(Heap& heap)
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: m_heap(heap)
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{
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m_heap.releaseAccess();
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}
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~ReleaseHeapAccessScope()
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{
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m_heap.acquireAccess();
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}
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private:
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Heap& m_heap;
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};
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} // namespace JSC
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