Bug 296822 NullProgressMonitor is not thread safe for expected usage
NullProgressMonitor.setCanceled and isCanceled access the cancelled field, but there's no synchronization. The expected use is that setCanceled is called from a thread other than the one doing the work, which polls isCanceled(), so this needs to be thread safe. Could either make these two methods synchronized or make the field volatile. Should check other progress monitor implementations too.
bundles/org.eclipse.jface/src/org/eclipse/jface/action/StatusLine.java
fTaskName = Util.ZERO_LENGTH_STRING;
		else
			fTaskName = name;
	}
	/**
	 * Makes the Cancel button visible.
	 * 
	 */
	protected void showButton() {
		if (fToolBar != null && !fToolBar.isDisposed()) {
			fToolBar.setVisible(true);
			fToolBar.setEnabled(true);
			fToolBar.setCursor(fStopButtonCursor);
			fCancelButtonIsVisible = true;
		}
	}
	/**
	 * Shows the Cancel button and ProgressIndicator.
	 * 
	 */
	protected void showProgress() {
		if (!fProgressIsVisible && !isDisposed()) {
			fProgressIsVisible = true;
			if (fCancelEnabled) {
				showButton();
			}
			if (fProgressBarComposite != null
					&& !fProgressBarComposite.isDisposed()) {
				fProgressBarComposite.setVisible(true);
			}