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
} else if (hasSubtask) {
    		return escapeMetaCharacters(fSubTaskName);
    	
    	} else {
    		return ""; 
    	}
    }
    /**
     * Implements <code>IProgressMonitor.worked</code>.
     * @see IProgressMonitor#worked(int)
     */
    public void worked(int work) {
        internalWorked(work);
    }
    /* (non-Javadoc)
     * @see org.eclipse.core.runtime.IProgressMonitorWithBlocking#clearBlocked()
     */
    public void clearBlocked() {
        blockedStatus = null;
        updateLabel();
    }
    /* (non-Javadoc)
     * @see org.eclipse.core.runtime.IProgressMonitorWithBlocking#setBlocked(org.eclipse.core.runtime.IStatus)
     */
    public void setBlocked(IStatus reason) {
        blockedStatus = reason;
        updateLabel();
    }
}