The kernel attempts to print a message when a leap second is inserted or removed. This can cause kernel versions prior to 2.6.29 to hang, due to a deadlock on xtime_lock. See http://lkml.org/lkml/2009/1/2/373 for a trace and explanation. The simplest solution for the older RHEL kernels is probably just to remove the leap second printks.
See comments in 479695, the RHEL5 version of this BZ. P.
Created attachment 330351 [details] RHEL4 fix for this issue
Proposed for RHEL 4.8, based on comment #3.
This request was evaluated by Red Hat Product Management for inclusion in a Red Hat Enterprise Linux maintenance release. Product Management has requested further review of this request by Red Hat Engineering, for potential inclusion in a Red Hat Enterprise Linux Update release for currently deployed products. This request is not yet committed for inclusion in an Update release.
Committed in 83.EL . RPMS are available at http://people.redhat.com/vgoyal/rhel4/
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-2009-1024.html