ajax在IE下同时设置async=false和beforeSend时假死

    If you make an ajax call using the option async:false and beforeSend for example to show a loader, it'l work with FF and Opera but not in IE and Chrome

use below：
1.
function firstStep(){
     var def = new jQuery.Deferred();
     var systime=new Date().getTime();
     $.ajax({
type: "POST",
url: '${ctx}/cn/xxx.action?systime='+systime,
data: {depCityCode: cityCode,depCity: cityName},
success: function(optStatus){
                //TODO ....
def.resolve();
}
      });
      return def;
}

2.******

$.when(firstStep()).then(function(){
//TODO ....
});