8204142: AWT hang occurs when sequenced events arrive out of sequence in multiple AppContexts

Summary: Improvements on the synchronization of SequencedEvent events from different AppContexts
Reviewed-by: serb

src/share/classes/java/awt/SequencedEvent.java

 /*
- * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -25,6 +25,7 @@
 
 package java.awt;
 
+import java.util.Iterator;
 import java.util.LinkedList;
 import sun.awt.AWTAccessor;
 import sun.awt.AppContext;
@@ -54,6 +55,7 @@ class SequencedEvent extends AWTEvent implements ActiveEvent {
     private final AWTEvent nested;
     private AppContext appContext;
     private boolean disposed;
+    private final LinkedList<AWTEvent> pendingEvents = new LinkedList<>();
 
     static {
         AWTAccessor.setSequencedEventAccessor(new AWTAccessor.SequencedEventAccessor() {
@@ -66,6 +68,35 @@ class SequencedEvent extends AWTEvent implements ActiveEvent {
         });
     }
 
+    private static final class SequencedEventsFilter implements EventFilter {
+        private final SequencedEvent currentSequencedEvent;
+        private SequencedEventsFilter(SequencedEvent currentSequencedEvent) {
+            this.currentSequencedEvent = currentSequencedEvent;
+        }
+        @Override
+        public FilterAction acceptEvent(AWTEvent ev) {
+            if (ev.getID() == ID) {
+                // Move forward dispatching only if the event is previous
+                // in SequencedEvent.list. Otherwise, hold it for reposting later.
+                synchronized (SequencedEvent.class) {
+                    Iterator<SequencedEvent> it = list.iterator();
+                    while (it.hasNext()) {
+                        SequencedEvent iev = it.next();
+                        if (iev.equals(currentSequencedEvent)) {
+                            break;
+                        } else if (iev.equals(ev)) {
+                            return FilterAction.ACCEPT;
+                        }
+                    }
+                }
+            } else if (ev.getID() == SentEvent.ID) {
+                return FilterAction.ACCEPT;
+            }
+            currentSequencedEvent.pendingEvents.add(ev);
+            return FilterAction.REJECT;
+        }
+    }
+
     /**
      * Constructs a new SequencedEvent which will dispatch the specified
      * nested event.
@@ -104,11 +135,8 @@ class SequencedEvent extends AWTEvent implements ActiveEvent {
                 if (EventQueue.isDispatchThread()) {
                     EventDispatchThread edt = (EventDispatchThread)
                         Thread.currentThread();
-                    edt.pumpEvents(SentEvent.ID, new Conditional() {
-                        public boolean evaluate() {
-                            return !SequencedEvent.this.isFirstOrDisposed();
-                        }
-                    });
+                    edt.pumpEventsForFilter(() -> !SequencedEvent.this.isFirstOrDisposed(),
+                            new SequencedEventsFilter(this));
                 } else {
                     while(!isFirstOrDisposed()) {
                         synchronized (SequencedEvent.class) {
@@ -197,10 +225,6 @@ class SequencedEvent extends AWTEvent implements ActiveEvent {
             }
             disposed = true;
         }
-        // Wake myself up
-        if (appContext != null) {
-            SunToolkit.postEvent(appContext, new SentEvent());
-        }
 
         SequencedEvent next = null;
 
@@ -221,5 +245,9 @@ class SequencedEvent extends AWTEvent implements ActiveEvent {
         if (next != null && next.appContext != null) {
             SunToolkit.postEvent(next.appContext, new SentEvent());
         }
+
+        for(AWTEvent e : pendingEvents) {
+            SunToolkit.postEvent(appContext, e);
+        }
     }
 }

test/java/awt/event/SequencedEvent/MultipleContextsFunctionalTest.java

+/*
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code 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 General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ * @test
+ * @bug 8204142
+ * @summary Deadlock when queueing SequencedEvent of different AppContexts
+ * @author Laurent Bourges
+ * @modules java.desktop/sun.awt
+ * @run main/othervm/timeout=30 MultipleContextsFunctionalTest
+ */
+
+import java.awt.BorderLayout;
+import java.awt.Dimension;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicReference;
+import javax.swing.JButton;
+import javax.swing.JFrame;
+import javax.swing.JLabel;
+import javax.swing.SwingUtilities;
+import javax.swing.Timer;
+
+public final class MultipleContextsFunctionalTest {
+
+    private static final long serialVersionUID = 1L;
+
+    private static final int NUM_WINDOW = 2;
+    private static final int INTERVAL = 50;
+    private static final int MAX_TIME = 10000; // 10s
+    private static final int TOLERANCE = 10000;// 10s
+    private static final int CHECK_LAPSE = 100;
+    private static final int MAX_COUNT = MAX_TIME / INTERVAL;
+    private static final int EXPECTED = MAX_COUNT * NUM_WINDOW;
+    private static final List<TestWindow> WINDOWS = new ArrayList<TestWindow>();
+
+    public static void main(String[] args) {
+        for (int i = 0; i < NUM_WINDOW; i++) {
+            createWin(i);
+        }
+
+        int total = 0;
+        int waitingTime = MAX_TIME + TOLERANCE;
+        while (waitingTime > 0 && total != EXPECTED) {
+            try {
+                Thread.sleep(CHECK_LAPSE);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+            waitingTime -= CHECK_LAPSE;
+
+            total = 0;
+            for (TestWindow window : WINDOWS) {
+                total += window.getCounter();
+            }
+        }
+
+        // Failure if AWT hanging: assert
+        System.out.println("Total [" + total + "] - Expected [" + EXPECTED + "]");
+        if (total == EXPECTED) {
+            System.out.println("Test PASSED");
+            return;
+        }
+        System.out.println("Test FAILED");
+        Runtime.getRuntime().halt(-1);
+    }
+
+    private static void createWin(int tgNum) {
+        new Thread(new ThreadGroup("TG " + tgNum),
+                new Runnable() {
+            @Override
+            public void run() {
+                sun.awt.SunToolkit.createNewAppContext();
+
+                final AtomicReference<TestWindow> ref =
+                        new AtomicReference<TestWindow>();
+
+                SwingUtilities.invokeLater(new Runnable() {
+                    @Override
+                    public void run() {
+                        final TestWindow window = new TestWindow(tgNum);
+                        window.setVisible(true);
+                        ref.set(window);
+                        WINDOWS.add(window);
+                    }
+                });
+
+                // Wait for window to show
+                TestWindow window = ref.get();
+                while (window == null) {
+                    try {
+                        Thread.sleep(100);
+                    } catch (InterruptedException ie) {
+                        ie.printStackTrace();
+                    }
+                    window = ref.get();
+                }
+                window.enableTimer(true);
+            }
+        }).start();
+    }
+
+    private static final class TestWindow extends JFrame implements ActionListener {
+
+        private final JButton btn;
+        private int counter = 0;
+        private final Timer t;
+
+        TestWindow(final int num) {
+            super("Test Window [" + num + "]");
+            setMinimumSize(new Dimension(300, 200));
+            setLocation(100 + 400 * (num - 1), 100);
+
+            setLayout(new BorderLayout());
+            JLabel textBlock = new JLabel("Lorem ipsum dolor sit amet...");
+            add(textBlock);
+
+            btn = new JButton("TEST");
+            add(btn, BorderLayout.SOUTH);
+
+            setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+            pack();
+
+            t = new Timer(INTERVAL, this);
+            t.setRepeats(false);
+        }
+
+        @Override
+        public void actionPerformed(ActionEvent e) {
+            this.toFront();
+            btn.setText("TEST " + (++counter));
+            this.toBack();
+            if (counter < MAX_COUNT) {
+                enableTimer(true);
+            } else {
+                dispose();
+            }
+        }
+
+        void enableTimer(boolean enable) {
+            if (enable) {
+                t.start();
+            } else {
+                t.stop();
+            }
+        }
+
+        int getCounter() {
+            return counter;
+        }
+    }
+}

test/java/awt/event/SequencedEvent/MultipleContextsUnitTest.java

+/*
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code 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 General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+import java.awt.AWTEvent;
+import java.awt.event.InvocationEvent;
+import java.lang.reflect.Constructor;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.atomic.AtomicReference;
+
+import sun.awt.AppContext;
+import sun.awt.SunToolkit;
+
+/**
+ * @test
+ * @bug 8204142
+ * @author Sergey Bylokhov
+ * @modules java.desktop/sun.awt
+ * @run main/othervm/timeout=30 MultipleContextsUnitTest
+ */
+public final class MultipleContextsUnitTest {
+
+    private static final int COUNT = 20;
+    private static final AppContext[] apps = new AppContext[COUNT];
+    private static final CountDownLatch go = new CountDownLatch(1);
+    private static final CountDownLatch end = new CountDownLatch(COUNT);
+
+    private static volatile int createSENumber = 0;
+    private static volatile int dispatchSENumber = 0;
+
+    public static void main(final String[] args) throws Exception {
+        for (int i = 0; i < COUNT; i++) {
+            Thread t = testThread(i);
+            t.start();
+            t.join();
+        }
+
+        for (AppContext app : apps) {
+            SunToolkit.postEvent(app, new InvocationEvent(new Object(), () -> {
+                try {
+                    go.await();
+                } catch (InterruptedException e) {
+                    throw new RuntimeException(e);
+                }
+            }));
+        }
+
+        // eventOne - created first, but posted last
+        AWTEvent eventOne = getSequencedEvent();
+        {
+            // eventTwo and eventThree - posted in the reverse order
+            AppContext app = apps[1];
+            AWTEvent eventTwo = getSequencedEvent();
+            AWTEvent eventThree = getSequencedEvent();
+            SunToolkit.postEvent(app, eventThree);
+            SunToolkit.postEvent(app, eventTwo);
+            SunToolkit.postEvent(app, new InvocationEvent(new Object(), () -> {
+                System.err.println(AppContext.getAppContext());
+                end.countDown();
+            }));
+        }
+
+        for (int i = 2; i < apps.length; i++) {
+            // eventTwo and eventThree - posted in the correct order
+            AppContext app = apps[i];
+
+            AWTEvent eventTwo = getSequencedEvent();
+            SunToolkit.postEvent(app, eventTwo);
+
+            AtomicReference<Boolean> called1 = new AtomicReference(false);
+            AtomicReference<Boolean> called2 = new AtomicReference(false);
+            int num1 = createSENumber;
+            SunToolkit.postEvent(app, new InvocationEvent(new Object(), () -> {
+                if (dispatchSENumber < num1) {
+                    throw new RuntimeException("Dispatched too early");
+                }
+                called1.set(true);
+                if (called2.get()) {
+                    throw new RuntimeException("Second event is called before first");
+                }
+            }));
+            AWTEvent eventThree = getSequencedEvent();
+            SunToolkit.postEvent(app, eventThree);
+            int num2 = createSENumber;
+            SunToolkit.postEvent(app, new InvocationEvent(new Object(), () -> {
+                if (dispatchSENumber < num2) {
+                    throw new RuntimeException("Dispatched too early");
+                }
+                called2.set(true);
+                if (!called1.get()) {
+                    throw new RuntimeException("First event is not called before second");
+                }
+                System.err.println(AppContext.getAppContext());
+                end.countDown();
+            }));
+        }
+
+
+
+        // eventOne should flush all EDT
+        SunToolkit.postEvent(apps[0], eventOne);
+        SunToolkit.postEvent(apps[0], new InvocationEvent(new Object(), () -> {
+            System.err.println(AppContext.getAppContext());
+            end.countDown();
+        }));
+
+        go.countDown();
+
+        System.err.println("Start to wait");
+        end.await();
+        System.err.println("End to wait");
+    }
+
+    private static Thread testThread(int index) {
+        final ThreadGroup group = new ThreadGroup("TG " + index);
+        return new Thread(group, () -> {
+            apps[index] = SunToolkit.createNewAppContext();
+        });
+    }
+
+    private static AWTEvent getSequencedEvent()
+    {
+        int num = createSENumber++;
+
+        InvocationEvent wrapMe = new InvocationEvent(new Object(), () -> {
+            if (num != dispatchSENumber++) {
+                System.err.println("num: " + num);
+                System.err.println("dispatchSENumber: " + dispatchSENumber);
+                throw new RuntimeException("Wrong order");
+            }
+        });
+
+        try {
+            /*
+             * SequencedEvent is a package private class, which cannot be instantiated
+             * by importing. So use reflection to create an instance.
+             */
+            Class<? extends AWTEvent> seqClass = (Class<? extends AWTEvent>) Class.forName("java.awt.SequencedEvent");
+            Constructor<? extends AWTEvent>
+                    seqConst = seqClass.getConstructor(AWTEvent.class);
+            seqConst.setAccessible(true);
+            return seqConst.newInstance(wrapMe);
+        } catch (Throwable err) {
+            throw new RuntimeException("Unable to instantiate SequencedEvent",err);
+        }
+    }
+}