Note: This bug is displayed in read-only format because
the product is no longer active in Red Hat Bugzilla.
RHEL Engineering is moving the tracking of its product development work on RHEL 6 through RHEL 9 to Red Hat Jira (issues.redhat.com). If you're a Red Hat customer, please continue to file support cases via the Red Hat customer portal. If you're not, please head to the "RHEL project" in Red Hat Jira and file new tickets here. Individual Bugzilla bugs in the statuses "NEW", "ASSIGNED", and "POST" are being migrated throughout September 2023. Bugs of Red Hat partners with an assigned Engineering Partner Manager (EPM) are migrated in late September as per pre-agreed dates. Bugs against components "kernel", "kernel-rt", and "kpatch" are only migrated if still in "NEW" or "ASSIGNED". If you cannot log in to RH Jira, please consult article #7032570. That failing, please send an e-mail to the RH Jira admins at rh-issues@redhat.com to troubleshoot your issue as a user management inquiry. The email creates a ServiceNow ticket with Red Hat. Individual Bugzilla bugs that are migrated will be moved to status "CLOSED", resolution "MIGRATED", and set with "MigratedToJIRA" in "Keywords". The link to the successor Jira issue will be found under "Links", have a little "two-footprint" icon next to it, and direct you to the "RHEL project" in Red Hat Jira (issue links are of type "https://issues.redhat.com/browse/RHEL-XXXX", where "X" is a digit). This same link will be available in a blue banner at the top of the page informing you that that bug has been migrated.
Cause
RHEL6 kernels have additional futex flags, FUTEX_PRIVATE_FLAG and
FUTEX_CLOCK_REALTIME in the syscall.futex $op argument.
Consequence
Without filtering out FUTEX_PRIVATE_FLAG and
FUTEX_CLOCK_REALTIME the script does not record data on RHEL6.
Fix
The futexes.stp added filtering for FUTEX_PRIVATE_FLAG and
FUTEX_CLOCK_REALTIME.
Result
The futexes.stp example now runs correctly on RHEL6.
DescriptionKim van der Riet
2011-03-11 14:31:14 UTC
The RHEL 6 System Tap Beginners Guide in section 4.4 "Identifying Contended User-Space Locks" includes an example script futexes.stp. However, this script will not return any results as written when run on RHEL 6, as it has not accounted for the FUTEX_PRIVATE_FLAG which newer kernels now use.
The update is fairly trivial, but the examples in our current documentation should work out-of-the-box.
Perhaps there are other example scripts that need updating too.
Created attachment 483740[details]
Modified script
The attached script works ok on RHEL 6 (although it is likely not very elegantly written and can be cleaned up).
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:
Cause
RHEL6 kernels have additional futex flags, FUTEX_PRIVATE_FLAG and
FUTEX_CLOCK_REALTIME in the syscall.futex $op argument.
Consequence
Without filtering out FUTEX_PRIVATE_FLAG and
FUTEX_CLOCK_REALTIME the script does not record data on RHEL6.
Fix
The futexes.stp added filtering for FUTEX_PRIVATE_FLAG and
FUTEX_CLOCK_REALTIME.
Result
The futexes.stp example now runs correctly on RHEL6.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
http://rhn.redhat.com/errata/RHBA-2011-1517.html