clone EventDispatchThreadMonitor from https://github.com/floscher/swinghelper
Change-Id: I103c250957555913bda2ebe58b8d3a56af172377
diff --git a/src/main/java/org/jdesktop/swinghelper/debug/EventDispatchThreadHangMonitor.java b/src/main/java/org/jdesktop/swinghelper/debug/EventDispatchThreadHangMonitor.java
new file mode 100644
index 0000000..47541af
--- /dev/null
+++ b/src/main/java/org/jdesktop/swinghelper/debug/EventDispatchThreadHangMonitor.java
@@ -0,0 +1,463 @@
+/*
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+package org.jdesktop.swinghelper.debug;
+
+import java.awt.*;
+import java.awt.event.*;
+import java.lang.management.*;
+import java.util.*;
+import java.util.Timer;
+
+import javax.swing.*;
+
+/**
+ * Monitors the AWT event dispatch thread for events that take longer than
+ * a certain time to be dispatched.
+ * <p/>
+ * The principle is to record the time at which we start processing an event,
+ * and have another thread check frequently to see if we're still processing.
+ * If the other thread notices that we've been processing a single event for
+ * too long, it prints a stack trace showing what the event dispatch thread
+ * is doing, and continues to time it until it finally finishes.
+ * <p/>
+ * This is useful in determining what code is causing your Java application's
+ * GUI to be unresponsive.
+ *
+ * <p>The original blog can be found here<br>
+ * <a href="http://elliotth.blogspot.com/2005/05/automatically-detecting-awt-event.html">
+ * Automatically detecting AWT event dispatch thread hangs</a>
+ * </p>
+ *
+ * @author Elliott Hughes <enh@jessies.org>
+ *
+ * Advice, bug fixes, and test cases from
+ * Alexander Potochkin and Oleg Sukhodolsky.
+ *
+ * https://swinghelper.dev.java.net/
+ */
+public final class EventDispatchThreadHangMonitor extends EventQueue {
+ private static final EventDispatchThreadHangMonitor INSTANCE = new EventDispatchThreadHangMonitor();
+
+ // Time to wait between checks that the event dispatch thread isn't hung.
+ private static final long CHECK_INTERVAL_MS = 100;
+
+ // Maximum time we won't warn about. This used to be 500 ms, but 1.5 on
+ // late-2004 hardware isn't really up to it; there are too many parts of
+ // the JDK that can go away for that long (often code that has to be
+ // called on the event dispatch thread, like font loading).
+ private static final long UNREASONABLE_DISPATCH_DURATION_MS = 1000;
+
+ // Help distinguish multiple hangs in the log, and match start and end too.
+ // Only access this via getNewHangNumber.
+ private static int hangCount = 0;
+
+ // Prevents us complaining about hangs during start-up, which are probably
+ // the JVM vendor's fault.
+ private boolean haveShownSomeComponent = false;
+
+ // The currently outstanding event dispatches. The implementation of
+ // modal dialogs is a common cause for multiple outstanding dispatches.
+ private final LinkedList<DispatchInfo> dispatches = new LinkedList<DispatchInfo>();
+
+ private static class DispatchInfo {
+ // The last-dumped hung stack trace for this dispatch.
+ private StackTraceElement[] lastReportedStack;
+ // If so; what was the identifying hang number?
+ private int hangNumber;
+
+ // The EDT for this dispatch (for the purpose of getting stack traces).
+ // I don't know of any API for getting the event dispatch thread,
+ // but we can assume that it's the current thread if we're in the
+ // middle of dispatching an AWT event...
+ // We can't cache this because the EDT can die and be replaced by a
+ // new EDT if there's an uncaught exception.
+ private final Thread eventDispatchThread = Thread.currentThread();
+
+ // The last time in milliseconds at which we saw a dispatch on the above thread.
+ private long lastDispatchTimeMillis = System.currentTimeMillis();
+
+ public DispatchInfo() {
+ // All initialization is done by the field initializers.
+ }
+
+ public void checkForHang() {
+ if (timeSoFar() > UNREASONABLE_DISPATCH_DURATION_MS) {
+ examineHang();
+ }
+ }
+
+ // We can't use StackTraceElement.equals because that insists on checking the filename and line number.
+ // That would be version-specific.
+ private static boolean stackTraceElementIs(StackTraceElement e, String className, String methodName, boolean isNative) {
+ return e.getClassName().equals(className) && e.getMethodName().equals(methodName) && e.isNativeMethod() == isNative;
+ }
+
+ // Checks whether the given stack looks like it's waiting for another event.
+ // This relies on JDK implementation details.
+ private boolean isWaitingForNextEvent(StackTraceElement[] currentStack) {
+ return stackTraceElementIs(currentStack[0], "java.lang.Object", "wait", true) && stackTraceElementIs(currentStack[1], "java.lang.Object", "wait", false) && stackTraceElementIs(currentStack[2], "java.awt.EventQueue", "getNextEvent", false);
+ }
+
+ private void examineHang() {
+ StackTraceElement[] currentStack = eventDispatchThread.getStackTrace();
+
+ if (isWaitingForNextEvent(currentStack)) {
+ // Don't be fooled by a modal dialog if it's waiting for its next event.
+ // As long as the modal dialog's event pump doesn't get stuck, it's okay for the outer pump to be suspended.
+ return;
+ }
+
+ if (stacksEqual(lastReportedStack, currentStack)) {
+ // Don't keep reporting the same hang every time the timer goes off.
+ return;
+ }
+
+ hangNumber = getNewHangNumber();
+ String stackTrace = stackTraceToString(currentStack);
+ lastReportedStack = currentStack;
+ Log.warn("(hang #" + hangNumber + ") event dispatch thread stuck processing event for " + timeSoFar() + " ms:" + stackTrace);
+ checkForDeadlock();
+ }
+
+ private static boolean stacksEqual(StackTraceElement[] a, StackTraceElement[] b) {
+ if (a == null) {
+ return false;
+ }
+ if (a.length != b.length) {
+ return false;
+ }
+ for (int i = 0; i < a.length; ++i) {
+ if (a[i].equals(b[i]) == false) {
+ return false;
+ }
+ }
+ return true;
+ }
+
+ /**
+ * Returns how long this dispatch has been going on (in milliseconds).
+ */
+ private long timeSoFar() {
+ return (System.currentTimeMillis() - lastDispatchTimeMillis);
+ }
+
+ public void dispose() {
+ if (lastReportedStack != null) {
+ Log.warn("(hang #" + hangNumber + ") event dispatch thread unstuck after " + timeSoFar() + " ms.");
+ }
+ }
+ }
+
+ private EventDispatchThreadHangMonitor() {
+ initTimer();
+ }
+
+ /**
+ * Sets up a timer to check for hangs frequently.
+ */
+ private void initTimer() {
+ final long initialDelayMs = 0;
+ final boolean isDaemon = true;
+ Timer timer = new Timer("EventDispatchThreadHangMonitor", isDaemon);
+ timer.schedule(new HangChecker(), initialDelayMs, CHECK_INTERVAL_MS);
+ }
+
+ private class HangChecker extends TimerTask {
+ @Override
+ public void run() {
+ synchronized (dispatches) {
+ if (dispatches.isEmpty() || !haveShownSomeComponent) {
+ // Nothing to do.
+ // We don't destroy the timer when there's nothing happening
+ // because it would mean a lot more work on every single AWT
+ // event that gets dispatched.
+ return;
+ }
+ // Only the most recent dispatch can be hung; nested dispatches
+ // by their nature cause the outer dispatch pump to be suspended.
+ dispatches.getLast().checkForHang();
+ }
+ }
+ }
+
+ /**
+ * Sets up hang detection for the event dispatch thread.
+ */
+ public static void initMonitoring() {
+ Toolkit.getDefaultToolkit().getSystemEventQueue().push(INSTANCE);
+ }
+
+ /**
+ * Overrides EventQueue.dispatchEvent to call our pre and post hooks either
+ * side of the system's event dispatch code.
+ */
+ @Override
+ protected void dispatchEvent(AWTEvent event) {
+ try {
+ preDispatchEvent();
+ super.dispatchEvent(event);
+ } finally {
+ postDispatchEvent();
+ if (!haveShownSomeComponent &&
+ event instanceof WindowEvent && event.getID() == WindowEvent.WINDOW_OPENED) {
+ haveShownSomeComponent = true;
+ }
+ }
+ }
+
+ private void debug(String which) {
+ if (false) {
+ for (int i = dispatches.size(); i >= 0; --i) {
+ System.out.print(' ');
+ }
+ System.out.println(which);
+ }
+ }
+
+ /**
+ * Starts tracking a dispatch.
+ */
+ private synchronized void preDispatchEvent() {
+ debug("pre");
+ synchronized (dispatches) {
+ dispatches.addLast(new DispatchInfo());
+ }
+ }
+
+ /**
+ * Stops tracking a dispatch.
+ */
+ private synchronized void postDispatchEvent() {
+ synchronized (dispatches) {
+ // We've finished the most nested dispatch, and don't need it any longer.
+ DispatchInfo justFinishedDispatch = dispatches.removeLast();
+ justFinishedDispatch.dispose();
+
+ // The other dispatches, which have been waiting, need to be credited extra time.
+ // We do this rather simplistically by pretending they've just been redispatched.
+ Thread currentEventDispatchThread = Thread.currentThread();
+ for (DispatchInfo dispatchInfo : dispatches) {
+ if (dispatchInfo.eventDispatchThread == currentEventDispatchThread) {
+ dispatchInfo.lastDispatchTimeMillis = System.currentTimeMillis();
+ }
+ }
+ }
+ debug("post");
+ }
+
+ private static void checkForDeadlock() {
+ ThreadMXBean threadBean = ManagementFactory.getThreadMXBean();
+ long[] threadIds = threadBean.findMonitorDeadlockedThreads();
+ if (threadIds == null) {
+ return;
+ }
+ Log.warn("deadlock detected involving the following threads:");
+ ThreadInfo[] threadInfos = threadBean.getThreadInfo(threadIds, Integer.MAX_VALUE);
+ for (ThreadInfo info : threadInfos) {
+ Log.warn("Thread #" + info.getThreadId() + " " + info.getThreadName() +
+ " (" + info.getThreadState() + ") waiting on " + info.getLockName() +
+ " held by " + info.getLockOwnerName() + stackTraceToString(info.getStackTrace()));
+ }
+ }
+
+ private static String stackTraceToString(StackTraceElement[] stackTrace) {
+ StringBuilder result = new StringBuilder();
+ // We used to avoid showing any code above where this class gets
+ // involved in event dispatch, but that hides potentially useful
+ // information when dealing with modal dialogs. Maybe we should
+ // reinstate that, but search from the other end of the stack?
+ for (StackTraceElement stackTraceElement : stackTrace) {
+ String indentation = " ";
+ result.append("\n" + indentation + stackTraceElement);
+ }
+ return result.toString();
+ }
+
+ private synchronized static int getNewHangNumber() {
+ return ++hangCount;
+ }
+
+ public static void main(String[] args) {
+ initMonitoring();
+ //special case for deadlock test
+ if (args.length > 0 && "deadlock".equals(args[0])) {
+ EventDispatchThreadHangMonitor.INSTANCE.haveShownSomeComponent = true;
+ Tests.runDeadlockTest();
+ return;
+ }
+ Tests.main(args);
+ }
+
+ private static class Tests {
+ public static void main(final String[] args) {
+
+ java.awt.EventQueue.invokeLater(new Runnable() {
+ public void run() {
+ for (String arg : args) {
+ final JFrame frame = new JFrame();
+ frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+ frame.setLocationRelativeTo(null);
+ if (arg.equals("exception")) {
+ runExceptionTest(frame);
+ } else if (arg.equals("focus")) {
+ runFocusTest(frame);
+ } else if (arg.equals("modal-hang")) {
+ runModalTest(frame, true);
+ } else if (arg.equals("modal-no-hang")) {
+ runModalTest(frame, false);
+ } else {
+ System.err.println("unknown regression test '" + arg + "'");
+ System.exit(1);
+ }
+ frame.pack();
+ frame.setVisible(true);
+ }
+ }
+ });
+ }
+
+ private static void runDeadlockTest() {
+ class Locker {
+ private Locker locker;
+
+ public void setLocker(Locker locker) {
+ this.locker = locker;
+ }
+
+ public synchronized void tryToDeadlock() {
+ locker.toString();
+ }
+
+ public synchronized String toString() {
+ try {
+ Thread.sleep(50);
+ } catch (InterruptedException e) {
+ e.printStackTrace();
+ }
+ return super.toString();
+ }
+ }
+ final Locker one = new Locker();
+ final Locker two = new Locker();
+ one.setLocker(two);
+ two.setLocker(one);
+
+ //Deadlock expected here:
+ for (int i = 0; i < 100; i++) {
+ SwingUtilities.invokeLater(new Runnable() {
+ public void run() {
+ one.tryToDeadlock();
+ }
+ });
+ two.tryToDeadlock();
+ }
+ }
+
+ // If we don't do our post-dispatch activity in a finally block, we'll
+ // report bogus hangs.
+ private static void runExceptionTest(final JFrame frame) {
+ JButton button = new JButton("Throw Exception");
+ button.addActionListener(new ActionListener() {
+ public void actionPerformed(ActionEvent e) {
+ // This shouldn't cause us to report a hang.
+ throw new RuntimeException("Nobody expects the Spanish Inquisition!");
+ }
+ });
+ frame.add(button);
+ }
+
+ // A demonstration of nested calls to dispatchEvent caused by SequencedEvent.
+ private static void runFocusTest(final JFrame frame) {
+ final JDialog dialog = new JDialog(frame, "Non-Modal Dialog");
+ dialog.add(new JLabel("Close me!"));
+ dialog.pack();
+ dialog.setLocationRelativeTo(frame);
+ dialog.addWindowFocusListener(new WindowAdapter() {
+ public void windowGainedFocus(WindowEvent e) {
+ System.out.println("FocusTest.windowGainedFocus");
+ // If you don't cope with nested calls to dispatchEvent, you won't detect this.
+ // See java.awt.SequencedEvent for an example.
+ sleep(2500);
+ }
+ });
+ JButton button = new JButton("Show Non-Modal Dialog");
+ button.addActionListener(new ActionListener() {
+ public void actionPerformed(ActionEvent e) {
+ dialog.setVisible(true);
+ }
+ });
+ frame.add(button);
+ }
+
+ // A demonstration of the problems of dealing with modal dialogs.
+ private static void runModalTest(final JFrame frame, final boolean shouldSleep) {
+ System.out.println(shouldSleep ? "Expect hangs!" : "There should be no hangs...");
+ JButton button = new JButton("Show Modal Dialog");
+ button.addActionListener(new ActionListener() {
+ public void actionPerformed(ActionEvent e) {
+ if (shouldSleep) {
+ sleep(2500); // This is easy.
+ }
+ JDialog dialog = new JDialog(frame, "Modal dialog", true);
+ dialog.setLayout(new FlowLayout());
+ dialog.add(new JLabel("Close this dialog!"));
+ final JLabel label = new JLabel(" ");
+ dialog.add(label);
+ dialog.pack();
+ dialog.setLocation(frame.getX() - 100, frame.getY());
+
+ // Make sure the new event pump has some work to do, each unit of which is insufficient to cause a hang.
+ new Thread(new Runnable() {
+ public void run() {
+ for (int i = 0; i <= 100000; ++i) {
+ final int value = i;
+ EventQueue.invokeLater(new Runnable() {
+ public void run() {
+ label.setText(Integer.toString(value));
+ }
+ });
+ }
+ }
+ }).start();
+
+ dialog.setVisible(true);
+
+ if (shouldSleep) {
+ sleep(2500); // If you don't distinguish different stack traces, you won't report this.
+ }
+ }
+ });
+ frame.add(button);
+ }
+
+ private static void sleep(long ms) {
+ try {
+ System.out.println("Sleeping for " + ms + " ms on " + Thread.currentThread() + "...");
+ Thread.sleep(ms);
+ System.out.println("Finished sleeping...");
+ } catch (Exception ex) {
+ ex.printStackTrace();
+ }
+ }
+ }
+
+ private static class Log {
+ public static void warn(String str) {
+ System.out.println(str);
+ }
+ }
+}
