Gameboy仿真-SwingWorker卡在Unsafe.park

Question

我正在为Gameboy系统制作模拟器，并且正在使用Swing作为GUI。 我的实现使用SwingWorker在后台线程中运行CPU仿真。 通过SwingWorker.doInBackground方法，我以规则的时间间隔（每当Gameboy模拟VBlank屏幕刷新时）发布一个包含帧缓冲区（图像数据）的数组，该数组应该每秒发生60次。 我在此后台线程中调用Thread.sleep(...)以将Gameboys时间与系统时间同步。 在process方法中，我将此数据传递到JPanel并调用其repaint方法。 我的doInBackground方法基本上是一个无限循环，其中模拟的Gameboy CPU在后台不断执行指令。

我面临的问题是在某些ROM上，我的应用程序冻结了，而我的JPanel组件没有显示任何屏幕更新。 我尝试在后台运行线程上使用println ，以输出由仿真CPU执行的指令，并且卡住了一段时间后也没有生成任何输出。

对于某些ROM，我完全看不到此问题。

这是我的SwingWorker代码的示例：

package com.sankar.gbemu.swing;

import com.sankar.gbemu.cpu.CPU;
import com.sankar.gbemu.gpu.LCDController;
import com.sankar.gbemu.gpu.VBlankListener;
import java.util.List;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;

public class EmulationWorker extends SwingWorker<Void,int[][]> {


private CPU cpu;
private LCDController lcd;
private GBPanel panel;
private GBRenderer renderer;

public EmulationWorker(CPU cpu, LCDController lcd, GBPanel panel, GBRenderer renderer) {
    this.cpu = cpu;
    this.lcd = lcd;
    this.panel = panel;
    this.renderer = renderer;
    init();
}

private void init() {
    lcd.registerVBlankListener(new VBlankListener() {

        private long lastRefresh = System.nanoTime();

        private static final long REFRESH_INTERVAL = (long)1e9/60;

        @Override
        public void vBlankOccured(int[][] screenData) {
            publish(screenData);

            long currentTime = System.nanoTime();
            long delta = currentTime - lastRefresh;

            lastRefresh = currentTime;

            if (delta < REFRESH_INTERVAL) {
                try {
                    long sleepInterval = (long)((REFRESH_INTERVAL - delta)/1e6);
                    Thread.sleep(sleepInterval);
                } catch(InterruptedException e) {
                    // Ignore
                }
            }
        }
    });
}

@Override
protected Void doInBackground() throws Exception {
    while(true) cpu.step();
}

@Override
protected void process(List<int[][]> updates) {
    if (!SwingUtilities.isEventDispatchThread()) throw new RuntimeException("Not in event dispatch thread");
    renderer.updateScreenData(updates.get(updates.size() - 1));
    panel.repaint();
}

}

我进行了jstack跟踪，发现我的swing-worker-thread停留在Unsafe.park：

2013-10-10 22:17:18
Full thread dump Java HotSpot(TM) 64-Bit Server VM (24.0-b56 mixed mode):

"Attach Listener" daemon prio=5 tid=0x00007fae12049000 nid=0xc20f waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"TimerQueue" daemon prio=5 tid=0x00007fae1240b800 nid=0xbf03 waiting on condition [0x000000015a085000]
   java.lang.Thread.State: WAITING (parking)
    at sun.misc.Unsafe.park(Native Method)
    - parking to wait for  <0x000000013ac88b60> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
    at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)
    at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2043)
    at java.util.concurrent.DelayQueue.take(DelayQueue.java:209)
    at javax.swing.TimerQueue.run(TimerQueue.java:171)
    at java.lang.Thread.run(Thread.java:724)

"SwingWorker-pool-1-thread-1" daemon prio=5 tid=0x00007fae11194800 nid=0xb92f waiting on condition [0x0000000159f82000]
   java.lang.Thread.State: WAITING (parking)
    at sun.misc.Unsafe.park(Native Method)
    - parking to wait for  <0x000000013ac2c340> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
    at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)
    at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2043)
    at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442)
    at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1068)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:724)

"Java2D Disposer" daemon prio=5 tid=0x00007fae11183000 nid=0xac03 in Object.wait() [0x0000000157915000]
   java.lang.Thread.State: WAITING (on object monitor)
    at java.lang.Object.wait(Native Method)
    - waiting on <0x000000013ad250c0> (a java.lang.ref.ReferenceQueue$Lock)
    at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:135)
    - locked <0x000000013ad250c0> (a java.lang.ref.ReferenceQueue$Lock)
    at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:151)
    at sun.java2d.Disposer.run(Disposer.java:145)
    at java.lang.Thread.run(Thread.java:724)

"Java2D Queue Flusher" daemon prio=5 tid=0x00007fae11106800 nid=0x9f0b in Object.wait() [0x0000000156eb0000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
    at java.lang.Object.wait(Native Method)
    - waiting on <0x000000013ac57f18> (a sun.java2d.opengl.OGLRenderQueue$QueueFlusher)
    at sun.java2d.opengl.OGLRenderQueue$QueueFlusher.run(OGLRenderQueue.java:208)
    - locked <0x000000013ac57f18> (a sun.java2d.opengl.OGLRenderQueue$QueueFlusher)

"DestroyJavaVM" prio=5 tid=0x00007fae12003000 nid=0x1007 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"AWT-EventQueue-0" prio=5 tid=0x00007fae110ec800 nid=0x9d03 waiting on condition [0x0000000156dad000]
   java.lang.Thread.State: WAITING (parking)
    at sun.misc.Unsafe.park(Native Method)
    - parking to wait for  <0x000000013ac8b3f0> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
    at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186)
    at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2043)
    at java.awt.EventQueue.getNextEvent(EventQueue.java:543)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:211)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

"AWT-Shutdown" prio=5 tid=0x00007fae110d5800 nid=0x6e03 in Object.wait() [0x0000000154562000]
   java.lang.Thread.State: WAITING (on object monitor)
    at java.lang.Object.wait(Native Method)
    - waiting on <0x000000013ad26900> (a java.lang.Object)
    at java.lang.Object.wait(Object.java:503)
    at sun.awt.AWTAutoShutdown.run(AWTAutoShutdown.java:287)
    - locked <0x000000013ad26900> (a java.lang.Object)
    at java.lang.Thread.run(Thread.java:724)

"AppKit Thread" daemon prio=5 tid=0x00007fae12120000 nid=0x2617 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Service Thread" daemon prio=5 tid=0x00007fae12081000 nid=0x5703 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"C2 CompilerThread1" daemon prio=5 tid=0x00007fae12078800 nid=0x5503 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"C2 CompilerThread0" daemon prio=5 tid=0x00007fae1207f000 nid=0x5303 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Signal Dispatcher" daemon prio=5 tid=0x00007fae12077800 nid=0x5103 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Finalizer" daemon prio=5 tid=0x00007fae12043000 nid=0x3e03 in Object.wait() [0x000000015283c000]
   java.lang.Thread.State: WAITING (on object monitor)
    at java.lang.Object.wait(Native Method)
    - waiting on <0x000000013ac08d80> (a java.lang.ref.ReferenceQueue$Lock)
    at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:135)
    - locked <0x000000013ac08d80> (a java.lang.ref.ReferenceQueue$Lock)
    at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:151)
    at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:189)

"Reference Handler" daemon prio=5 tid=0x00007fae12040800 nid=0x3c03 in Object.wait() [0x0000000152739000]
   java.lang.Thread.State: WAITING (on object monitor)
    at java.lang.Object.wait(Native Method)
    - waiting on <0x000000013ac08ad0> (a java.lang.ref.Reference$Lock)
    at java.lang.Object.wait(Object.java:503)
    at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:133)
    - locked <0x000000013ac08ad0> (a java.lang.ref.Reference$Lock)

"VM Thread" prio=5 tid=0x00007fae12040000 nid=0x3a03 runnable 

"GC task thread#0 (ParallelGC)" prio=5 tid=0x00007fae1200f800 nid=0x3603 runnable 

"GC task thread#1 (ParallelGC)" prio=5 tid=0x00007fae12010000 nid=0x3803 runnable 

"VM Periodic Task Thread" prio=5 tid=0x00007fae12089800 nid=0x5903 waiting on condition 

JNI global references: 344

我不确定什么可能出错了，因为我所有的Swing组件更新都仅在EventDispatch线程上完成。

我正在运行适用于Mac OS X Mountain Lion的Java（TM）SE运行时环境（内部版本1.7.0_40-b43），这是可用的最新版本。

Answer 1

doInBackground方法实际上引发了异常。 由于我没有实现done方法，而没有使用get获得结果，因此该异常被吞没并且没有引起注意。