Applied patch to rhel5.4 on x96-64 host, built, and ran some IO to 41 targets for a few minutes w/ dt verifying data integrity.  No problems noticed.

in kernel-2.6.18-164.11.1.el5

testing RPMs including this patch based on 164.10.1 are available here:

http://people.redhat.com/jpirko/test/bz549906/

Thanks. We'll pull a copy for test.

(In reply to comment #16)
> Thanks. We'll pull a copy for test.    

thanks, Wayne,
what's the status of it, now?

In test.

Updated to kernel patch 2.6.18-164.10.1.el5.bz549906, performed 3 times of portdown on both vmax and dmx3, the issue not encountered

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-2010-0046.html