Quoting <4CCFD63D0200007800020366.novell.com> from xen-devel (http://lists.xensource.com/archives/html/xen-devel/2010-11/msg00046.html): "There is a race in net_tx_build_mops between checking if net_schedule_list is empty and actually dequeuing the first entry on the list. If another thread dequeues the only entry on the list during this window we crash because list_first_entry expects a non-empty list, like so: [...]" Once upstream merges the patch in the email, backport it to RHEL5.7.
Upstream commit: http://xenbits.xensource.com/linux-2.6.18-xen.hg?rev/1045
Another patch to backport in order to fix the compilation failure caused by the previous patch: - msgid: 4CD1809B02000078000206A7.novell.com, - URL: http://lists.xensource.com/archives/html/xen-devel/2010-11/msg00127.html (Not yet committed by upstream.)
list_first_entry() is already in RHEL5's "include/linux/list.h" (twice, for that matter), so Comment 2 is superfluous.
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.
in kernel-2.6.18-243.el5 You can download this test kernel (or newer) from http://people.redhat.com/jwilson/el5 Detailed testing feedback is always welcomed.
Could we possibly reproduce this issue on an unpatched kernel? How can we intentionally make the race condition happen? Thanks.
Hello Jinxin, (In reply to comment #8) > Could we possibly reproduce this issue on an unpatched kernel? How can we > intentionally make the race condition happen? Please follow the link under comment 5 and look at the "Testing" section in my message there -- you'll see that unfortunately I was unable to trigger the race, even though I tried to modify the kernel to achieve that.
OK. Since this is hard to reproduce even on intentionally modified kernel, and our acceptance test against Xen shows that the patch didn't seem to cause any slowdown or other problems to the guest's network, I'll put this to VERIFIED if there's no harm to take this patch and it is believed to solve some potential problem.
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-2011-1065.html