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/*
* Copyright (C) 2013-2023 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.
*/
#include "config.h"
#include "Watchdog.h"
#include "VM.h"
#include <wtf/CPUTime.h>
#include <wtf/TZoneMallocInlines.h>
namespace JSC {
WTF_MAKE_TZONE_ALLOCATED_IMPL(Watchdog);
Watchdog::Watchdog(VM* vm)
: m_vm(vm)
{
}
void Watchdog::setTimeLimit(Seconds limit, ShouldTerminateCallback callback, void* data1, void* data2)
{
ASSERT(m_vm->currentThreadIsHoldingAPILock());
m_timeLimit = limit;
m_callback = callback;
m_callbackData1 = data1;
m_callbackData2 = data2;
if (m_hasEnteredVM && hasTimeLimit())
startTimer(m_timeLimit);
}
bool Watchdog::shouldTerminate(JSGlobalObject* globalObject)
{
ASSERT(m_vm->currentThreadIsHoldingAPILock());
Seconds epsilon;
#if OS(WINDOWS)
// We can reach this point as much as 15ms before the deadline on Windows,
// in which case the watchdog will never get to do its job.
// Adding this leeway shouldn't cause a problem for other platforms
// (since the "deadline is infinity" case should be the crucial one),
// but it is a fact that only Windows is experiencing the issue.
epsilon = Seconds::fromMilliseconds(20);
#endif
if (MonotonicTime::timePointFromNow(epsilon) < m_deadline)
return false; // Just a stale timer firing. Nothing to do.
// Set m_deadline to MonotonicTime::infinity() here so that we can reject all future
// spurious wakes.
m_deadline = MonotonicTime::infinity();
auto cpuTime = CPUTime::forCurrentThread();
if (cpuTime < m_cpuDeadline) {
auto remainingCPUTime = m_cpuDeadline - cpuTime;
startTimer(remainingCPUTime);
return false;
}
// Note: we should not be holding the lock while calling the callbacks. The callbacks may
// call setTimeLimit() which will try to lock as well.
// If m_callback is not set, then we terminate by default.
// Else, we let m_callback decide if we should terminate or not.
bool needsTermination = !m_callback
|| m_callback(globalObject, m_callbackData1, m_callbackData2);
if (needsTermination)
return true;
// If we get here, then the callback above did not want to terminate execution. As a
// result, the callback may have done one of the following:
// 1. cleared the time limit (i.e. watchdog is disabled),
// 2. set a new time limit via Watchdog::setTimeLimit(), or
// 3. did nothing (i.e. allow another cycle of the current time limit).
//
// In the case of 1, we don't have to do anything.
// In the case of 2, Watchdog::setTimeLimit() would already have started the timer.
// In the case of 3, we need to re-start the timer here.
ASSERT(m_hasEnteredVM);
bool callbackAlreadyStartedTimer = (m_cpuDeadline != noTimeLimit);
if (hasTimeLimit() && !callbackAlreadyStartedTimer)
startTimer(m_timeLimit);
return false;
}
bool Watchdog::hasTimeLimit()
{
return (m_timeLimit != noTimeLimit);
}
void Watchdog::enteredVM()
{
m_hasEnteredVM = true;
if (hasTimeLimit())
startTimer(m_timeLimit);
}
void Watchdog::exitedVM()
{
ASSERT(m_hasEnteredVM);
stopTimer();
m_hasEnteredVM = false;
}
void Watchdog::startTimer(Seconds timeLimit)
{
ASSERT(m_hasEnteredVM);
ASSERT(m_vm->currentThreadIsHoldingAPILock());
ASSERT(hasTimeLimit());
ASSERT(timeLimit <= m_timeLimit);
m_cpuDeadline = CPUTime::forCurrentThread() + timeLimit;
auto now = MonotonicTime::now();
auto deadline = now + timeLimit;
if ((now < m_deadline) && (m_deadline <= deadline))
return; // Wait for the current active timer to expire before starting a new one.
// Else, the current active timer won't fire soon enough. So, start a new timer.
m_deadline = deadline;
// We need to ensure that the Watchdog outlives the timer.
// For the same reason, the timer may also outlive the VM that the Watchdog operates on.
// So, we always need to null check m_vm before using it. The VM will notify the Watchdog
// via willDestroyVM() before it goes away.
VMTraps::queue().dispatchAfter(timeLimit, [protectedThis = Ref { *this }] {
Locker locker { protectedThis->m_lock };
if (protectedThis->m_vm)
protectedThis->m_vm->notifyNeedWatchdogCheck();
});
}
void Watchdog::stopTimer()
{
ASSERT(m_hasEnteredVM);
ASSERT(m_vm->currentThreadIsHoldingAPILock());
m_cpuDeadline = noTimeLimit;
}
void Watchdog::willDestroyVM(VM* vm)
{
Locker locker { m_lock };
ASSERT_UNUSED(vm, m_vm == vm);
m_vm = nullptr;
}
} // namespace JSC
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