RHBA-2013:0386 - Bug Fix Advisory

Topic

Updated tuned packages that fix several bugs are now available for Red Hat
Enterprise Linux 6.

Description

The tuned packages contain a daemon that tunes system settings dynamically. It
does so by monitoring the usage of several system components periodically.

This update fixes the following bugs:

• Red Hat Enterprise Linux 6.1 and later enters processor power-saving states

more aggressively. This could result in a small performance penalty on certain
workloads. With this update, the pmqos-static.py daemon has been added to the
tuned packages, which allows to set the requested latency using the kernel Power
Management QoS interface. It is run when the "latency-performance" profile is
activated and it sets cpu_dma_latency=0, which keeps the CPU in C0 state, thus
making the system as responsive as possible. (BZ#714180)

• When the ELEVATOR_TUNE_DEVS option was set to a disk device in the

/etc/sysconfig/ktune file instead of providing a disk scheduler control file,
the scheduler setting was not written to a disk scheduler control file but
directly into the disk device file. Consequently, contents of the disk could
become corrupted. With this update, the value of ELEVATOR_TUNE_DEVS is checked
and only the disk scheduler control file is allowed for writing. As a result, an
invalid value of ELEVATOR_TUNE_DEVS is detected in the described scenario so
that the disk contents damage can be prevented. (BZ#784308)

• When the tuned daemon run with the "enterprise-storage" profile enabled and a

non-root, non-boot disk partition from a device with write-back cache was
mounted, tuned remounted the partition with the "nobarriers" option. If a power
failure occurred at that time, the file system could become corrupted. With this
update, tuned can detect usage of write-back cache on devices communicating with
kernel via SCSI. In these cases, "nobarriers" is now disabled, thus preventing
this bug in the described scenario. (BZ#801561)

• Previously, when the tuned service was started, the tuned PID file was created

with world-writable permissions. This bug has been fixed and the
/var/run/tuned/tuned.pid file is now created with correct permissions as
expected. (BZ#845336)

• On a machine with hot-plug disk devices with the "enterprise-storage" profile

activated, a new disk device could be added into the system, or the disk could
be removed and inserted back. In such a scenario, the scheduler and read-ahead
settings from the profile were not applied on the newly-added disks. With this
update, a new udev rule has been added, which restarts the ktune daemon whenever
a new disk device is added, thus fixing this bug. (BZ#847445)

• The transparent hugepage kernel thread could interfere with latency-sensitive

applications. To lower the latency, the transparent hugepages are now disabled
in the latency-performance tuned profile. (BZ#887355)

• Previously, non-root, non-boot partitions were re-mounted using the

"nobarrier" option to improve performance. On virtual guests, this could lead to
data corruption if power supply was suddenly interrupted, because there was
usually a host cache in transfer. This bug has been fixed and the virtual-guest
profile no longer re-mounts partitions using "nobarrier". (BZ#886956)

Users of tuned are advised to upgrade to these updated packages, which fix these
bugs.

Solution

Before applying this update, make sure all previously-released errata
relevant to your system have been applied.

This update is available via the Red Hat Network. Details on how to
use the Red Hat Network to apply this update are available at
https://access.redhat.com/knowledge/articles/11258

Affected Products

• Red Hat Enterprise Linux Server 6 x86_64
• Red Hat Enterprise Linux Server 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 i386
• Red Hat Enterprise Linux Workstation 6 x86_64
• Red Hat Enterprise Linux Workstation 6 i386
• Red Hat Enterprise Linux Desktop 6 x86_64
• Red Hat Enterprise Linux Desktop 6 i386
• Red Hat Enterprise Linux for IBM z Systems 6 s390x
• Red Hat Enterprise Linux for Power, big endian 6 ppc64
• Red Hat Enterprise Linux for Scientific Computing 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support (for IBM z Systems) 6 s390x

Fixes

• BZ - 784308 - ktune breaks disks when pecifying just the device (e. g. /dev/sda) for ELEVATOR_TUNE_DEVS
• BZ - 801561 - tuned-adm enterprise-storage should not disable barriers on devices with write back cache
• BZ - 845336 - /var/run/tuned/tuned.pid created with insecure permissions
• BZ - 887355 - disable transparent hugepages in latency-performance profile

CVEs

• CVE-2012-6136

References

(none)