Occasional InterruptedException when quitting a Swing application

Question

I recently updated my computer to a more powerful one, with a quad-core hyperthreading processor (i7), thus plenty of real concurrency available. Now I'm occasionally getting the following error when quitting (System.exit(0)) an application (with a Swing GUI) that I'm developing:

Exception while removing reference: java.lang.InterruptedException
java.lang.InterruptedException
        at java.lang.Object.wait(Native Method)
        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:118)
        at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:134)
        at sun.java2d.Disposer.run(Disposer.java:125)
        at java.lang.Thread.run(Thread.java:619)

Well, given that it started to happen with a more concurrency-capable hardware, and it has to do with threads, and it happens occasionally, it's obviously some kind of timing thing. But the problem is that the stack trace is so short. All I have is the listing above. It doesn't include my own code at all, so it's somewhat hard to guess where the bug is.

Has anyone experienced something like this before? Any ideas how to start solving it?

Edit: Since quitting a Swing application with System.exit(0) may be "unclean", but I don't want to set the main frame to EXIT_ON_CLOSE because I want to ensure that there's nothing critical going on when the application quits, I added a mechanism so that it executes the main frame's dispose() method before calling System.exit(0). So it should be pretty clean now, but the occasional exception still happens. It happens after the System.exit(0) has been called; dispose() works with no problems. That is, it must be coming from a shutdown hook:

mainFrame.dispose(); // No problem! After this returns, all visible GUI is gone.
// In fact, if there were no other threads around, the VM could terminate here.
System.exit(0); // Throws an InterruptedException from sun.java2d.Disposer.run

I even tried explicitly disposing all Windows by looping through Window.getWindows() array (it contains ownerless Dialogs and such), but it made no difference. This issue seems to have little to do with "cleanness" (i.e. explicitly releasing native screen resources before quitting). It's something else, but what?

Edit 2: Setting the default close operation to EXIT_ON_CLOSE made no difference. http://www.google.com/search?q=sun.java2d.Disposer.run(Disposer.java:125) finds a few bug reports, so maybe this indeed is a bug in Sun's Java2D implementation. I could imagine that bugs like this can go unfixed for a long time, because they're pretty harmless in practice; an exception from a shutdown hook hardly hurts anyone else. Given that this happens in a GUI app, the exception is not even noticed unless the stderr is directed to a console or log.

Answer 1

Your Disposer is blocked in a call to remove() (removing the next platform native resource). This means that the disposer thread (a daemon thread) is not being shutdown naturally when the VM exits (which you should expect since you are terminating it via System.exit()).

You have a non-daemon thread in your application which is keeping the VM from exiting when all your swing windows have been disposed.

Solution: find it and cause it to exit.

Normally a swing application exits gracefully if all of its swing windows have been disposed of, for example, this program will pop a window then exit once it is closed (all with no call to System.exit()):

public static void main(String args[]) throws Exception {
    JFrame jf = new JFrame();
    jf.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
    jf.setVisible(true);
}

You might also try running the garbage collector before exiting, just for kicks.