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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. ``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
* 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.
*/
#pragma once
#include <utility>
#include <wtf/IterationStatus.h>
namespace JSC {
class VM;
using StopTheWorldStatus = std::pair<IterationStatus, VM*>;
#define STW_RESUME_ALL_TOKEN reinterpret_cast<VM*>(1)
// StopTheWorldCallback return values:
#define STW_CONTINUE() StopTheWorldStatus(IterationStatus::Continue, nullptr)
#define STW_CONTEXT_SWITCH(targetVM) StopTheWorldStatus(IterationStatus::Continue, targetVM)
#define STW_RESUME_ONE(targetVM) StopTheWorldStatus(IterationStatus::Done, targetVM)
#define STW_RESUME_ALL() StopTheWorldStatus(IterationStatus::Done, STW_RESUME_ALL_TOKEN)
#define STW_RESUME() StopTheWorldStatus(IterationStatus::Done, nullptr)
enum class StopTheWorldEvent : uint8_t {
VMCreated,
VMActivated,
VMStopped,
};
// The VMManager Stop the World (STW) mechanism will call handlers of this shape once the world
// is stopped. The handler is expected to return one of the above StopTheWorldStatus results.
//
// STW_CONTINUE means that the handler expects to be called again on the same thread, unless
// an external agent requestResumeAll. In practice, this result is not really useful except
// for tests.
//
// STW_CONTEXT_SWITCH means that the handler wants to switch to another thread as specified
// by the targetVM. The VMManager will stop the current thread, and call the handler back
// from the targetVM thread while all threads remain stopped (Stopped mode).
//
// STW_RESUME_ONE means that the handler wants a specific thread to start running while all
// other VM threads remain stopped (RunOne mode). This may or may not result in a deadlock,
// as the targetVM thread to run may be blocked on resources held by other VM threads that
// remain stopped. It is the responsibility of the client to detect if this occurs (perhaps
// with a timeout), and call VMManager::requestResumeAll() to unblock the deadlock of necessary.
//
// STW_RESUME_ALL means that the handler wants all VM threads to resume execution after
// this (RunAll mode).
//
// STW_RESUME means that the handler wants to resume execution with previous mode (either
// RunAll or RunOne mode).
using StopTheWorldCallback = StopTheWorldStatus (*)(VM&, StopTheWorldEvent);
} // namespace JSC
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