Monday, May 24, 2010

Unresponse threading involving Swing and AWT-EventQueue

Programmer Question

I have an application that is unresponsive and seems to be in a deadlock or something like a deadlock. See the two threads below. Notice that the My-Thread@101c thread blocks AWT-EventQueue-0@301. However, My-Thread has just called java.awt.EventQueue.invokeAndWait(). So AWT-EventQueue-0 blocks My-Thread (I believe).



My-Thread@101c, priority=5, in group 'main', status: 'WAIT'
blocks AWT-EventQueue-0@301
at java.lang.Object.wait(Object.java:-1)
at java.lang.Object.wait(Object.java:485)
at java.awt.EventQueue.invokeAndWait(Unknown Source:-1)
at javax.swing.SwingUtilities.invokeAndWait(Unknown Source:-1)
at com.acme.ui.ViewBuilder.renderOnEDT(ViewBuilder.java:157)
.
.
.
at com.acme.util.Job.run(Job.java:425)
at java.lang.Thread.run(Unknown Source:-1)

AWT-EventQueue-0@301, priority=6, in group 'main', status: 'MONITOR'
waiting for My-Thread@101c
at com.acme.persistence.TransactionalSystemImpl.executeImpl(TransactionalSystemImpl.java:134)
.
.
.
at com.acme.ui.components.MyTextAreaComponent$MyDocumentListener.insertUpdate(MyTextAreaComponent.java:916)
at javax.swing.text.AbstractDocument.fireInsertUpdate(Unknown Source:-1)
at javax.swing.text.AbstractDocument.handleInsertString(Unknown Source:-1)
at javax.swing.text.AbstractDocument$DefaultFilterBypass.replace(Unknown Source:-1)
at javax.swing.text.DocumentFilter.replace(Unknown Source:-1)
at com.acme.ui.components.FilteredDocument$InputDocumentFilter.replace(FilteredDocument.java:204)
at javax.swing.text.AbstractDocument.replace(Unknown Source:-1)
at javax.swing.text.JTextComponent.replaceSelection(Unknown Source:-1)
at javax.swing.text.DefaultEditorKit$DefaultKeyTypedAction.actionPerformed(Unknown Source:-1)
at javax.swing.SwingUtilities.notifyAction(Unknown Source:-1)
at javax.swing.JComponent.processKeyBinding(Unknown Source:-1)
at javax.swing.JComponent.processKeyBindings(Unknown Source:-1)
at javax.swing.JComponent.processKeyEvent(Unknown Source:-1)
at java.awt.Component.processEvent(Unknown Source:-1)
at java.awt.Container.processEvent(Unknown Source:-1)
at java.awt.Component.dispatchEventImpl(Unknown Source:-1)
at java.awt.Container.dispatchEventImpl(Unknown Source:-1)
at java.awt.Component.dispatchEvent(Unknown Source:-1)
at java.awt.KeyboardFocusManager.redispatchEvent(Unknown Source:-1)
at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(Unknown Source:-1)
at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(Unknown Source:-1)
at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(Unknown Source:-1)
at java.awt.DefaultKeyboardFocusManager.dispatchEvent(Unknown Source:-1)
at java.awt.Component.dispatchEventImpl(Unknown Source:-1)
at java.awt.Container.dispatchEventImpl(Unknown Source:-1)
at java.awt.Window.dispatchEventImpl(Unknown Source:-1)
at java.awt.Component.dispatchEvent(Unknown Source:-1)
at java.awt.EventQueue.dispatchEvent(Unknown Source:-1)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source:-1)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source:-1)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source:-1)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source:-1)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source:-1)
at java.awt.EventDispatchThread.run(Unknown Source:-1)


Here is the TransactionalSystemImpl.executeImpl method:



private synchronized Object executeImpl(Transaction xact, boolean commit) {
final Object result;

try {
if (commit) { // this is line 134
clock.latch();
synchronized(pendingEntries) {
if (xactLatchCount > 0) {
pendingEntries.add(xact);
} else {
xactLog.write(new TransactionEntry(xact, clock.time()));
}
}
}

final TransactionExecutor executor = transactionExecutorFactory.create(
xact.getClass().getSimpleName()
);

if (executor == null) {
throw new IllegalStateException("Failed to create transaction executor for transaction: " + xact.getClass().getName());
}

result = executor.execute(xact);

} finally {
if (commit) clock.unlatch();
}

return result;
}


Does anyone know what's going on here or how to fix it?



Find the answer here

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