This bug has been copied from bug #624068 and has been proposed to be backported to 5.5 z-stream (EUS).
in kernel 2.6.18-194.20.1.el5 linux-2.6-md-dm-fix-deadlock-with-fsync-vs-resize-in-lvm.patch
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-2010-0839.html
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: Running the Virtual Desktop Server Manager (VDSM) and performing an lvextend during an intensive Virtual Guest power up caused this operation to fail. Since lvextend was blocked, all components became non-responsive: vgs and lvs commands froze the session, Virtual Guests became Paused or Not Responding. This was caused by a faulty use of a lock. With this update, performing an lvextend operation works as expected.