XMLHttpRequest take 100% cpu during sync call

When I use the XMLHttpRequest to get data from a server synchroniously.
Firefox will use 100% cpu waiting for the request to finish.

This is a problem as the server and client machine are the same. The
server operation cannot perform as firefor tries to use the cpu 100%
while waiting..



I checked the code and found in nsXMLHttpRequest.cpp line 1532:

  // If we're synchronous, spin an event loop here and wait
  if (!(mState & XML_HTTP_REQUEST_ASYNC)) {
    while (mState & XML_HTTP_REQUEST_SYNCLOOPING) {
      modalEventQueue->ProcessPendingEvents();
    }

    mEventQService->PopThreadEventQueue(modalEventQueue);
  }

This looks like a loop, but should this take 100% cpu ?
Is there something that can be done about this ? (apart from going to
async...) ?

regards,

Kees