Relative to quarterly update 4, several improvements have been incorporated into the Unbreakable Enterprise Kernel to support Xen usage:

The Unbreakable Enterprise Kernel supports a wide range of hardware and devices. In close cooperation with hardware and storage vendors, several device drivers have been updated by Oracle.

The following features included in the Unbreakable Enterprise Kernel Release 2 are still under development, but are made available for testing and evaluation purposes.

Oracle Linux maintains user-space compatibility with Red Hat Enterprise Linux, which is independent of the kernel version running underneath the operating system. Existing applications in user space will continue to run unmodified on the Unbreakable Enterprise Kernel Release 2 and no re-certifications are needed for RHEL certified applications.

From UEK R2 quarterly update 3 (2.6.39-400) onward, support for IB, OFED, and RDS is integrated into the kernel. The OFED userland RPMs continue to be provided, but the kernel-ib and ofa-kernel RPMs are no longer required.

The kernel ABI remains unchanged in all updates to UEK R2 subsequent to quarterly update 3.

To minimize impact on interoperability during releases, the Oracle Linux team works closely with third-party vendors whose hardware and software have dependencies on kernel modules. However, to allow the introduction of new drivers, there might be instances where changes must be made. Before installing this update, verify the support status of this release with your application vendor.

This update includes minor fixes for various software issues as well as security fixes for several CVEs. There are no major fixed issues of note.

This section describes known issues in this update.

ACPI

One some systems you might see ACPI-related error messages in dmesg similar to the following:

ACPI Error: [CDW1] Namespace lookup failure, AE_NOT_FOUND
        ACPI Error: Method parse/execution failed [_SB_._OSC||\||]
        ACPI Error: Field [CDW3] at 96 exceeds Buffer [NULL] size 64 (bits)]]>

These messages, which are not fatal, are caused by bugs in the BIOS. Contact your system vendor for a BIOS update. (Bug ID 13100702)

ASM

Calling the oracleasm init script, /etc/init.d/oracleasm, with the parameter scandisks can lead to error messages about missing devices similar to the following:

oracleasm-read-label: Unable to open device "device": No such file or directory

However, the device actually exists. You can ignore this error message, which is triggered by a timing issue. Only use the init script to start and stop the oracleasm service. All other options, such as scandisks, listdisk, and createdisk, are deprecated. For these and other administrative tasks, use /usr/sbin/oracleasm instead. (Bug ID 13639337)

bnx2x driver

When using the bnx2x driver in a bridge, disable Transparent Packet Aggregation (TPA) by including the statement options bnx2x disable_tpa=1 in /etc/modprobe.conf. (Bug ID 14626070)

Btrfs

CPU microcode update failures on PVM/PVHVM guests

When running Oracle Linux with UEK R2, you might see error messages in dmesg or /var/log/messages similar to this one:

microcode: CPU0 update to revision 0x6b failed.

You can ignore this warning. You do not need to upgrade the microcode for virtual CPUs as presented to the guest. (Bug ID 12576264, 13782843)

DHCP lease is not obtained at boot time

If DHCP lease negotiation takes more than 5 seconds at boot time, the following message is displayed:

ethX: failed. No link present. Check cable?

If the ethtool ethX command confirms that the interface is present, edit /etc/sysconfig/network-scripts/ifcfg-ethX and set LINKDELAY=N, where N is a value greater than 5 seconds (for example, 30 seconds). Alternatively, use NetworkManager to configure the interface. (Bug ID 16620177)

Emulex OneConnect UCNA Firmware Flashing

The request_firmware interface to the Emulex Ethernet driver for Emulex OneConnect adapters supports flash updating of the UCNA firmware image.

Oracle Linux 5 systems with the Unbreakable Enterprise Kernel require the ethtool-6-4.0.1.el5.arch.rpm version of the ethtool package, where arch is i386 or x86_64 as appropriate. The package is available from the ol5_i386_UEK_latest and ol5_x86_64_UEK_latest channels on the Unbreakable Linux Network (Advisory ELBA-2013-2544, released Aug 29, 2013) or from Oracle Public Yum at http://public-yum.oracle.com/repo/OracleLinux/OL5/latest.

Oracle Linux 6 systems with the Unbreakable Enterprise Kernel do not require a package update.

To update the UCNA firmware image:

Firmware warning message

You can safely ignore the following firmware warning message that might be displayed on some Sun hardware:

[Firmware Warn]: GHES: Poll interval is 0 for generic hardware error source:
1, disabled.

(Bug ID 13696512)

I/O scheduler

The Unbreakable Enterprise Kernel uses the deadline scheduler as the default I/O scheduler. For the Red Hat Compatible Kernel, the default I/O scheduler is the cfq scheduler.

InfiniBand warning messages when disabling a switch port

You might see the following warning messages if you use the ibportstate disable command to disable a switch port:

ibwarn: [2696] _do_madrpc: recv failed: Connection timed out
ibwarn: [2696] mad_rpc: _do_madrpc failed; dport (Lid 38)
ibportstate: iberror: failed: smp set portinfo failed

You can safely ignore these warnings. (Bug ID 16248314)

libfprint

The following message might appear in dmesg or /var/log/messages:

WARNING! power/level is deprecated; use power/control instead.

The USB subsystem in UEK R2 deprecates the power/level sysfs attribute in favor of the power/control attribute. The libfprint fingerprinting library triggers this warning via udev rules that try to use the old attribute first. You can safely ignore this warning. The setting of the appropriate power level still succeeds. (Bug ID 13523418)

Multipathed root disk

At boot time, the root file system is not writable when the multipathing service starts. As a result, the system cannot automatically generate the file /etc/multipath/wwids and the console displays a message similar to the following:

Cannot open file [/etc/multipath/wwids] readonly: No such file or directory

You can safely ignore this warning. The subsequent post-boot operation of multipathd and device-mapper-multipath is not affected.

To prevent this warning message from recurring, enter the following command as root to generate /etc/multipath/wwids after the system has booted:

# multipath -l

(Bug ID 17395420, 16076888)

NFSv4 and open(2) flag combinations that can cause a process to hang

If you specify both the O_RDONLY and O_TRUNC flags when opening a regular file in a mounted NFS version 4 file system,the calling process hangs. The workaround is not to use this combination of flags with regular files. O_TRUNC is intended for use with regular files where the open mode allows writing. (Bug ID 17412390)

Nouveau kernel driver is not compatible with NVIDIA graphics driver

After upgrading to UEK R2, the NVIDIA driver upgrade script does not correctly blacklist the Nouveau kernel driver. To blacklist the driver, append rdblacklist=nouveau nouveau.modeset=0 to the kernel boot parameters in /boot/grub/grub.conf.

NUMA warning messages on a non-NUMA system

You can safely ignore the following warning messages in dmesg and /var/log messages if you see them on a non-NUMA system:

kernel: NUMA: Warning: node ids are out of bound, from=-1 to=-1 distance=10
hcid[4293]: Register path:/org/bluez fallback:1
kernel: No NUMA configuration found

(Bug ID 13711370)

pcspkr driver error message

You can safely ignore the following error message:

Error: Driver 'pcspkr' is already registered, aborting...

The message arises from an alias conflict between snd-pcsp and pcspkr. To prevent the message from being displayed, add the following line to /etc/modprobe.d/blacklist.conf:

blacklist snd-pcsp

(Bug ID 10355937)

sched_yield() settings for CFS

For the Unbreakable Enterprise Kernel, kernel.sched_compat_yield=1 is set by default. For the Red Hat Compatible Kernel, kernel.sched_compat_yield=0 is used by default.

Soft lockup errors when booting

When upgrading or installing the UEK R2 kernel on fast hardware, usually with SAN storage attached, the kernel can fail to boot and BUG: soft lockup messages are displayed in the console log. The workaround is to increase the baud rate from the default value of 9600 by amending the kernel boot line in /boot/grub/grub.conf to include an appropriate console setting, for example:

console=ttyS0,115200n8

A value of 115200 is recommended as smaller values such as 19200 are known to be insufficient for some systems (for example, see http://docs.oracle.com/cd/E19045-01/blade.x6220/820-0048-18/sp.html#0_pgfId-1002490). If the host implements an integrated system management infrastructure, such as ILOM on Sun and Oracle systems or iLO on HP systems, configure the integrated console baud rate to match the setting for the host system. Otherwise, the integrated console is likely to display garbage characters. (Bug ID 17064059, 17252160)

Support for large memory 32-bit systems

Releases of Oracle Linux prior to Oracle Linux 5 supplied a hugemem kernel to allow a system to address up to 64 GB of memory in 32-bit mode. The hugemem kernel is no longer available in Oracle Linux 5 and later releases.

The Unbreakable Enterprise Kernel (UEK) supports a maximum of 16 GB of memory for 32-bit kernels on bare metal and hardware virtualized machine (HVM) systems, and 8 GB for fully paravirtualized machine (PVM) systems. 32-bit PVM guest operating systems must be located in the first 128 GB of physical memory on the host.

The Red Hat Compatible Kernel (RHCK) has the same limitations, except that PVM systems can have up to 16 GB of memory. The limitation of 8 GB for PVM on UEK was chosen for reasons of reliability.

A 32-bit system uses the PAE (physical address extension) memory feature to map physical memory beyond 4 GB into the 32-bit address space that is available to each process. A 64-bit system can address memory beyond 4 GB without requiring an extra layer of memory abstraction.

Oracle Linux on x86_64 includes 32-bit libraries, which allow applications built for both 64-bit and 32-bit Linux to run on the same system. This capability provides scalability to virtually unlimited memory sizes, while retaining the ability to run 32-bit applications. Oracle recommends this configuration for any system with more than 4 GB of memory. (Bug ID 16974301)

Transparent Huge Pages

This update removes the Transparent Huge Pages (THP) feature. Following extensive benchmarking and testing, Oracle found that THP caused a performance degradation for some workloads of between 5 and 10%. This performance degradation was a result of a slower memory allocator code path being used even when the applications were not using THP. When the fact that huge pages are not swappable was taken into account, the positive effect that THP should provide was outweighed by its negative effects.

After installing this update, you cannot enable THP (for example, by specifying kernel boot parameters). The THP settings under /sys/kernel/mm/transparent_hugepage have also been removed. A future update might contain an updated THP implementation which resolves the performance issue.

(Bug ID 17279055)

udev

A message similar to the following might be recorded in dmesg or /var/log/messages at boot time:

udevd (pid): /proc/pid/oom_adj is deprecated, please use /proc/pid/oom_score_adj instead.

The udev process uses the deprecated oom_adj kernel interface to prevent it from being killed if the system runs short of memory. You can safely ignore the message as the action still succeeds. To prevent the message from occurring, install the package udev-147-2.42.el6.arch.rpm or higher for Oracle Linux 6, or udev-095-14.29.0.1.el5.arch.rpm or higher for Oracle Linux 5. (Bug ID 13655071, 13712009)

Virtualization

XFS