JSF action method not completing if a new Thread was started

Question

I want a commandButton to call a method in my managed bean that will process something asynchronously (new Thread) then the request should complete immediately without waiting the new Thread to finish. I want this async code to execute for as long it needs, independent of the user session.

But the request doesn't complete and keeps waiting the Thread to finish, I don't understand why. Did I get something wrong here?

xhtml:

<p:commandButton 
    value="Update" 
    id="updateButtonId" 
    styleClass="internalButton" 
    action="#{myBean.processUpdate}"
    onstart="PF('loading').show()" 
    oncomplete="PF('loading').hide()"
    update="myDataTableId" />

Bean:

@ManagedBean(name="myBean")
@ViewScoped
public class MyBean {
    ...
    public void processUpdate(){

        Thread thread = new Thread(new Runnable() {
            @Override
            public void run() {
                //do something...           
            }
        });
        thread.start();
    }
}