JavaScriptCore-1218.tar.gz

[apple/javascriptcore.git] / runtime / Watchdog.cpp

diff --git a/runtime/Watchdog.cpp b/runtime/Watchdog.cpp
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+/*
+ * Copyright (C) 2013 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 "CallFrame.h"
+#include <wtf/CurrentTime.h>
+#include <wtf/MathExtras.h>
+
+namespace JSC {
+
+#define NO_LIMIT std::numeric_limits<double>::infinity()
+
+Watchdog::Watchdog()
+    : m_timerDidFire(false)
+    , m_didFire(false)
+    , m_limit(NO_LIMIT)
+    , m_startTime(0)
+    , m_elapsedTime(0)
+    , m_reentryCount(0)
+    , m_isStopped(true)
+    , m_callback(0)
+    , m_callbackData1(0)
+    , m_callbackData2(0)
+{
+    initTimer();
+}
+
+Watchdog::~Watchdog()
+{
+    ASSERT(!isArmed());
+    stopCountdown();
+    destroyTimer();
+}
+
+void Watchdog::setTimeLimit(VM& vm, double limit,
+    ShouldTerminateCallback callback, void* data1, void* data2)
+{
+    bool wasEnabled = isEnabled();
+
+    if (!m_isStopped)
+        stopCountdown();
+
+    m_didFire = false; // Reset the watchdog.
+
+    m_limit = limit;
+    m_callback = callback;
+    m_callbackData1 = data1;
+    m_callbackData2 = data2;
+
+    // If this is the first time that timeout is being enabled, then any
+    // previously JIT compiled code will not have the needed polling checks.
+    // Hence, we need to flush all the pre-existing compiled code.
+    //
+    // However, if the timeout is already enabled, and we're just changing the
+    // timeout value, then any existing JITted code will have the appropriate
+    // polling checks. Hence, there is no need to re-do this flushing.
+    if (!wasEnabled) {
+        // And if we've previously compiled any functions, we need to revert
+        // them because they don't have the needed polling checks yet.
+        vm.releaseExecutableMemory();
+    }
+
+    startCountdownIfNeeded();
+}
+
+bool Watchdog::didFire(ExecState* exec)
+{
+    if (m_didFire)
+        return true;
+
+    if (!m_timerDidFire)
+        return false;
+    m_timerDidFire = false;
+    stopCountdown();
+
+    double currentTime = currentCPUTime();
+    double deltaTime = currentTime - m_startTime;
+    double totalElapsedTime = m_elapsedTime + deltaTime;
+    if (totalElapsedTime > m_limit) {
+        // Case 1: the allowed CPU time has elapsed.
+
+        // 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(exec, m_callbackData1, m_callbackData2);
+        if (needsTermination) {
+            m_didFire = true;
+            return true;
+        }
+
+        // The m_callback may have set a new limit. So, we may need to restart
+        // the countdown.
+        startCountdownIfNeeded();
+
+    } else {
+        // Case 2: the allowed CPU time has NOT elapsed.
+
+        // Tell the timer to alarm us again when it thinks we've reached the
+        // end of the allowed time.
+        double remainingTime = m_limit - totalElapsedTime;
+        m_elapsedTime = totalElapsedTime;
+        m_startTime = currentTime;
+        startCountdown(remainingTime);
+    }
+
+    return false;
+}
+
+bool Watchdog::isEnabled()
+{
+    return (m_limit != NO_LIMIT);
+}
+
+void Watchdog::fire()
+{
+    m_didFire = true;
+}
+
+void Watchdog::arm()
+{
+    m_reentryCount++;
+    if (m_reentryCount == 1)
+        startCountdownIfNeeded();
+}
+
+void Watchdog::disarm()
+{
+    ASSERT(m_reentryCount > 0);
+    if (m_reentryCount == 1)
+        stopCountdown();
+    m_reentryCount--;
+}
+
+void Watchdog::startCountdownIfNeeded()
+{
+    if (!m_isStopped)
+        return; // Already started.
+
+    if (!isArmed())
+        return; // Not executing JS script. No need to start.
+
+    if (isEnabled()) {
+        m_elapsedTime = 0;
+        m_startTime = currentCPUTime();
+        startCountdown(m_limit);
+    }
+}
+
+void Watchdog::startCountdown(double limit)
+{
+    ASSERT(m_isStopped);
+    m_isStopped = false;
+    startTimer(limit);
+}
+
+void Watchdog::stopCountdown()
+{
+    if (m_isStopped)
+        return;
+    stopTimer();
+    m_isStopped = true;
+}
+
+Watchdog::Scope::Scope(Watchdog& watchdog)
+    : m_watchdog(watchdog)
+{
+    m_watchdog.arm();
+}
+
+Watchdog::Scope::~Scope()
+{
+    m_watchdog.disarm();
+}
+
+} // namespace JSC