Chapter 2 Known Issues

This chapter describes the known issues for the Unbreakable Enterprise Kernel Release 3.

ACFS

Oracle ASM Cluster File System (ACFS) is currently not supported for use with UEK R3. (Bug ID 16318126)

ACPI

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 or PVHVM guests

When running Oracle Linux 6 with UEK R3, 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)

dm-nfs obsoleted

In UEK R2, the dm-nfs module provided the ability to create a loopback device for a mounted NFS file or file system. For example, the feature allowed you to create the shared storage for an Oracle 3 VM cluster on an NFS file system. The dm-nfs module provided direct I/O to the server and bypassed the loop driver to avoid an additional level of page caching. The dm-nfs module is not provided with UEK R3. The loop driver can now provide the same I/O functionality as dm-nfs by extending the AIO interface to perform direct I/O. To create the loopback device, use the losetup command instead of dmsetup.

DTrace

ERST message

You can safely ignore the following message that might be displayed in syslog or dmesg:

ERST: Failed to get Error Log Address Range.

The message indicates that the system BIOS does not support an Error Record Serialization Table (ERST). (Bug ID 17034576)

ext4 inline data

The inline data feature that allows the data of small files to be stored inside their inodes is not yet available. The -O inline_data option to the mkfs.ext4 and tune2fs commands is not supported. (Bug ID 17210654)

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)

Huge pages

One-gigabyte (1 GB) huge pages are not currently supported for the following configurations:

Two-megabyte (2 MB) huge pages have been tested and work with these configurations.

(Bug ID 17299364, 17299871, 17271305)

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.

ioapic failure messages

You can safely ignore messages such as ioapic: probe of 0000:00:05.4 failed with error -22. Such messages are the result of the ioapic driver attempting to re-register I/O APIC PCI devices that were already registered at boot time. (Bug ID 17034993)

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)

IPoIB mode switching

The Internet Protocol over InfiniBand (IPoIB) driver supports the use of either connected mode or datagram mode with an interface, where datagram mode is the default mode. Changing the mode of an InfiniBand interface by echoing either connected or datagram to /sys/class/net/ibN/mode is not supported. It is also not possible to change the mode of an InfiniBand interface while it is enabled.

To change the IPoIB mode of an InfiniBand interface:

  1. Edit the /etc/sysconfig/network-scripts/ifcfg-ibN configuration file, where N is the number of the interface:

    • To configure connected mode, specify CONNECTED_MODE=yes in the file.

    • To configure datagram mode, either specify CONNECTED_MODE=no in the file or do not specify this setting at all (datagram mode is enabled by default).

    Note

    Before saving your changes, make sure that you have not specified more than one setting for CONNECTED_MODE in the file.

  2. To enable the specified mode on the interface, use the following commands to take down the interface and bring it back up:

    # ifdown ibN
    # ifup ibN

(Bug ID 17479833)

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 R3 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)

Large memory system fails to boot

If a large memory system fails to start, boot it using an alternate kernel to UEK R3 and disable the kdump service before booting into the UEK R3 kernel:

# chkconfig kdump off

(Bug ID 16765434)

Linux Containers (LXC)

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 R3 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)

Transparent Huge Pages

This release removes the Transparent Huge Pages (THP) feature. Following extensive benchmarking and testing, Oracle found that THP caused a performance degradation of between 5 and 10% for some workloads. 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 UEK release, 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.

Note

This change does not affect support for applications that use explicit huge pages (for example, Oracle Database).

(Bug ID 16823432)

User Namespaces

The kernel functionality (CONFIG_USER_NS) that allows unprivileged processes to create namespaces for users inside which they have root privileges is not currently implemented because of a clash with the implementation of XFS. This functionality is primarily intended for use with Linux Containers. As a result, the lxc-checkconfig command displays User namespace: missing. (Bug ID 16656850)

Virtualization

X.509 Certificates for module verification

The system reports a message similar to the following if there is a problem loading an in-kernel X.509 module verification certificate at boot time:

Loading module verification certificates 
X.509: Cert 0c21da3d73dcdbaffc799e3d26f3c846a3afdc43 is not yet valid 
MODSIGN: Problem loading in-kernel X.509 certificate (-129)

This error occurs because the hardware clock lags behind the system time as shown by hwclock, for example:

# hwclock
Tue 20 Aug 2013 01:41:40 PM EDT -0.767004 seconds

The solution is to set the hardware clock from the system time by running the following command:

# hwclock --systohc

After correcting the hardware clock, no error should be seen at boot time, for example:

Loading module verification certificates 
MODSIGN: Loaded cert 'Slarti: Josteldalsbreen signing key: 
0c21da3d73dcdbaffc799e3d26f3c846a3afdc43'

(Bug ID 17346862)