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/wizard/ProgressMonitorPart.java
fSubTaskName = name;
        updateLabel();
    }
    /**
     * Updates the label with the current task and subtask names.
     */
    protected void updateLabel() {
        if (blockedStatus == null) {
            String text = taskLabel();
            fLabel.setText(text);
        } else {
			fLabel.setText(blockedStatus.getMessage());
		}
        
        fLabel.update();
    }
    /**
     * Return the label for showing tasks
     * @return String
     */
    private String taskLabel() {
    	boolean hasTask= fTaskName != null && fTaskName.length() > 0;
    	boolean hasSubtask= fSubTaskName != null && fSubTaskName.length() > 0;
    	
		if (hasTask) {
			if (hasSubtask)
				return escapeMetaCharacters(JFaceResources.format(
    					"Set_SubTask", new Object[] { fTaskName, fSubTaskName }));
   			return escapeMetaCharacters(fTaskName);