p_0021' class='copiable-anchor'> &para;</a></span></dt>
<dd><p>The &rsquo;waiter&rsquo; argument is optional.  The &rsquo;worker&rsquo; argument is an event
loop running in a different thread than the one in which this
procedure is called, and is the one in which &rsquo;thunk&rsquo; will be executed
by posting an event to that loop.  The result of executing &rsquo;thunk&rsquo;
will then be posted to the event loop specified by the &rsquo;waiter&rsquo;
argument, or to the default event loop if no &rsquo;wait