This bug has been copied from bug #567479 and has been proposed to be backported to 5.5 z-stream (EUS).
in 2.6.18-194.6.1.el5
Technical note added. If any revisions are required, please edit the "Technical Notes" field accordingly. All revisions will be proofread by the Engineering Content Services team. New Contents: The Red Hat Enterprise Linux 5.5 kernel contained a fix for Bugzilla issue number 548657 which introduced a regression in file locking behavior that presented with the General Parallel File System (GPFS). This update removes the redundant locking code.
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-2010-0504.html