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/*
* Copyright (C) 2025 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#include "MicrotaskQueue.h"
#include "Debugger.h"
#include "JSCJSValueInlines.h"
#include "JSGlobalObject.h"
#include "JSObject.h"
#include "SlotVisitorInlines.h"
#include <wtf/SetForScope.h>
#include <wtf/TZoneMallocInlines.h>
WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN
namespace JSC {
WTF_MAKE_TZONE_ALLOCATED_IMPL(MicrotaskQueue);
bool QueuedTask::isRunnable() const
{
if (RefPtr dispatcher = m_dispatcher)
return dispatcher->isRunnable();
return true;
}
MicrotaskQueue::MicrotaskQueue(VM& vm)
{
vm.m_microtaskQueues.append(this);
}
MicrotaskQueue::~MicrotaskQueue()
{
if (isOnList())
remove();
}
template<typename Visitor>
void MicrotaskQueue::visitAggregateImpl(Visitor& visitor)
{
m_queue.visitAggregate(visitor);
m_toKeep.visitAggregate(visitor);
}
DEFINE_VISIT_AGGREGATE(MicrotaskQueue);
void MicrotaskQueue::enqueue(QueuedTask&& task)
{
auto* globalObject = task.globalObject();
auto microtaskIdentifier = task.identifier();
m_queue.enqueue(WTFMove(task));
if (globalObject) {
if (auto* debugger = globalObject->debugger(); debugger) [[unlikely]]
debugger->didQueueMicrotask(globalObject, microtaskIdentifier);
}
}
bool MarkedMicrotaskDeque::hasMicrotasksForFullyActiveDocument() const
{
for (auto& task : m_queue) {
if (task.isRunnable())
return true;
}
return false;
}
template<typename Visitor>
void MarkedMicrotaskDeque::visitAggregateImpl(Visitor& visitor)
{
// Because content in the queue will not be changed, we need to scan it only once per an entry during one GC cycle.
// We record the previous scan's index, and restart scanning again in CollectorPhase::FixPoint from that.
// When new GC phase begins, this cursor is reset to zero (beginMarking). This optimization is introduced because
// some of application have massive size of MicrotaskQueue depth. For example, in parallel-promises-es2015-native.js
// benchmark, it becomes 251670 at most.
// This cursor is adjusted when an entry is dequeued. And we do not use any locking here, and that's fine: these
// values are read by GC when CollectorPhase::FixPoint and CollectorPhase::Begin, and both suspend the mutator, thus,
// there is no concurrency issue.
for (auto iterator = m_queue.begin() + m_markedBefore, end = m_queue.end(); iterator != end; ++iterator) {
auto& task = *iterator;
visitor.appendUnbarriered(task.m_globalObject);
visitor.appendUnbarriered(task.m_job);
visitor.appendUnbarriered(task.m_arguments, QueuedTask::maxArguments);
}
m_markedBefore = m_queue.size();
}
DEFINE_VISIT_AGGREGATE(MarkedMicrotaskDeque);
} // namespace JSC
WTF_ALLOW_UNSAFE_BUFFER_USAGE_END
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