This bug has been copied from bug #559410 and has been proposed to be backported to 5.4 z-stream (EUS).
See bug 554735 for test cases and a proposed patch.
Please note that you'll need the followup patch for the Xen kernel as well. That was just posted, and should be integrated into the 5.5 kernel soon. Chris Lalancette
in 2.6.18-164.16.1.el5
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on therefore solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHSA-2010-0380.html