2.10. Kernel

kernel component
When booted off a qla4xxx device, upgrading from Red Hat Enterprise Linux 6.1 to Red Hat Enterprise Linux 6.2 will cause the system to fail to boot up with the new kernel. There are various ways to work around this issue:
  1. You have upgraded to Red Hat Enterprise Linux 6.2 and want the qla4xxx device firmware to manage discovering and logging in to iSCSI targets.
    1. Boot up the system with the Red Hat Enterprise Linux 6.1 kernel.
    2. Disable SysfsBoot for the qla4xxx device: 
      ~]# echo "options qla4xxx ql4xdisablesysfsboot=1" >> /etc/modprobe.d/qla4xxx.conf
    3. Rebuild initramfs for the Red Hat Enterprise Linux 6.2 kernel by re-installing the kernel: 
      ~]# yum -y reinstall kernel
  2. You have not upgraded to Red Hat Enterprise Linux 6.2 and want the qla4xxx device firmware to manage discovering and logging in to iSCSI targets.
    1. Boot up the system with the Red Hat Enterprise Linux 6.1 kernel.
    2. Disable SysfsBoot for the qla4xxx device: 
      ~]# echo "options qla4xxx ql4xdisablesysfsboot=1" >> /etc/modprobe.d/qla4xxx.conf
    3. Proceed with the upgrade to Red Hat Enterprise Linux 6.2.
  3. You have upgraded to Red Hat Enterprise Linux 6.2 and want to use open-iscsi to manage the qla4xxx discovery and login process.
    1. Boot up the system with the Red Hat Enterprise Linux 6.1 kernel.
    2. Install the iscsi-initiator-utils and dracut-network packages: 
      ~]# yum install -y dracut-network iscsi-initiator-utils
    3. Rebuild initramfs for the Red Hat Enterprise Linux 6.2 kernel by re-installing the kernel: 
      ~]# yum -y reinstall kernel
    4. Add the iscsi_firmware kernel option into GRUB's configuration: /boot/grub/menu.lst (for LILO, the Linux Loader, modify the /etc/lilo.conf file).
  4. You have not upgraded to Red Hat Enterprise Linux 6.2 and want to use open-iscsi to manage the qla4xxx discovery and login process.
    1. Install the iscsi-initiator-utils and dracut-network packages: 
      ~]# yum install -y dracut-network iscsi-initiator-utils
    2. Proceed with the upgrade to Red Hat Enterprise Linux 6.2.
    3. Add the iscsi_firmware kernel option into GRUB's configuration: /boot/grub/menu.lst (for LILO, the Linux Loader, modify the /etc/lilo.conf file).
kernel component, BZ#679262
In Red Hat Enterprise Linux 6.2, due to security concerns, addresses in /proc/kallsyms and /proc/modules show all zeros when accessed by a non-root user.
kernel component
Red Hat Enterprise Linux 6.1 PCI-Express Adapters may fail to configure on October 2011 GA IBM Power 7 systems. For more information, refer to https://access.redhat.com/site/solutions/66231.
kernel component
Superfluous information is displayed on the console due to a correctable machine check error occurring. This information can be safely ignored by the user. Machine check error reporting can be disabled by using the nomce kernel boot option, which disables machine check error reporting, or the mce=ignore_ce kernel boot option, which disables correctable machine check error reporting.
kernel component
The order in which PCI devices are scanned may change from one major Red Hat Enterprise Linux release to another. This may result in device names changing, for example, when upgrading from Red Hat Enterprise Linux 5 to 6. You must confirm that a device you refer to during installation, is the intended device.
One way to assure the correctness of device names is to, in some configurations, determine the mapping from the controller name to the controller's PCI address in the older release, and then compare this to the mapping in the newer release, to ensure that the device name is as expected.
The following is an example from /var/log/messages: 
kernel: cciss0: <0x3230> at PCI 0000:1f:00.0 IRQ 71 using DAC
…
kernel: cciss1: <0x3230> at PCI 0000:02:00.0 IRQ 75 using DAC
If the device name is incorrect, add the pci=bfsort parameter to the kernel command line, and check again.
kernel component
Enabling CHAP (Challenge-Handshake Authentication Protocol) on an iSCSI target for the be2iscsi driver results in kernel panic. To work around this issue, disable CHAP on the iSCSI target.
kernel component
Newer VPD (Vital Product Data) blocks can exceed the size the tg3 driver normally handles. As a result, some of the routines that operate on the VPD blocks may fail. For example, the nvram test fails when running the ethtool –t command on BCM5719 and BCM5720 Ethernet Controllers.
kernel component
Running the ethtool -t command on BCM5720 Ethernet controllers causes a loopback test failure because the tg3 driver does not wait long enough for a link.
kernel component
The tg3 driver in Red Hat Enterprise Linux 6.2 does not include support for Jumbo frames and TSO (TCP Segmentation Offloading) on BCM5719 Ethernet controllers. As a result, the following error message is returned when attempting to configure, for example, Jumbo frames: 
SIOCSIFMTU: Invalid argument
kernel component
The default interrupt configuration for the Emulex LPFC FC/FCoE driver has changed from INT-X to MSI-X. This is reflected by the lpfc_use_msi module parameter (in /sys/class/scsi_host/host#/lpfc_use_msi) being set to 2 by default, instead of the previous 0.
Two issues provide motivation for this change: SR-IOV capability only works with the MSI-X interrupt mode, and certain recent platforms only support MSI or MSI-X.
However, the change to the LPFC default interrupt mode can bring out host problems where MSI/MSI-X support is not fully functional. Other host problems can exist when running in the INT-X mode.
If any of the following symptoms occur after upgrading to, or installing Red Hat Enterprise Linux 6.2 with an Emulex LPFC adapter in the system, change the value of the lpfc module parameter, lpfc_use_msi, to 0:
  • The initialization or attachment of the lpfc adapter may fail with mailbox errors. As a result, the lpfc adapter is not configured on the system. The following message appear in /var/log/messages: 
    lpfc 0000:04:08.0: 0:0:0443 Adapter failed to set maximum DMA length mbxStatus x0
lpfc 0000:04:08.0: 0:0446 Adapter failed to init (255), mbxCmd x9 CFG_RING, mbxStatus x0, ring 0
lpfc 0000:04:08.0: 0:1477 Failed to set up hba
ACPI: PCI interrupt for device 0000:04:08.0 disabled
  • While the lpfc adapter is operating, it may fail with mailbox errors, resulting in the inability to access certain devices. The following message appear in /var/log/messages: 
    lpfc 0000:0d:00.0: 0:0310 Mailbox command x5 timeout Data: x0 x700 xffff81039ddd0a00
lpfc 0000:0d:00.0: 0:0345 Resetting board due to mailbox timeout
lpfc 0000:0d:00.0: 0:(0):2530 Mailbox command x23 cannot issue Data: xd00 x2
  • Performing a warm reboot causes any subsequent boots to halt or stop because the BIOS is detecting the lpfc adapter. The system BIOS logs the following messages: 
    Installing Emulex BIOS ......
Bringing the Link up, Please wait...
Bringing the Link up, Please wait...
kernel component
The minimum firmware version for NIC adapters managed by netxen_nic is 4.0.550. This includes the boot firmware which is flashed in option ROM on the adapter itself.
kernel component
The kdump kernel occasionally panics on a DELL PowerEdge R810 system with the i686 architecture.
kernel component
Running the LTP (Linux Testing Project) cgroup test suite on certain AMD systems causes NMI Watchdog to detect a hard LOCKUP and cause kernel panic.
kernel component, BZ#683012
High stress on 64-bit IBM POWER series machines prevents kdump from successfully capturing the vmcore. As a result, the second kernel is not loaded, and the system becomes unresponsive.
kernel component
Loading and unloading edac modules in a loop on certain HP systems may cause kernel panic.
kernel component
If the storage driver is loaded before multipathd is started, I/O errors occur. To work around this issue, use one of the following kernel command line parameters which are consumed by dracut: 
rdloaddriver=scsi_dh_emc
or 
rdloaddriver=scsi_dh_rdac
or 
rdloaddriver=scsi_dh_emc,scsi_dh_rdac
The above command line parameters will cause the scsi_dh module to load before multipath is started.
kernel component
Triggering kdump to capture a vmcore through the network using the Intel 82575EB ethernet device in a 32 bit environment causes the networking driver to not function properly in the kdump kernel, and prevent the vmcore from being captured.
kernel component, BZ#701857
Attempting to hibernate certain laptops, including Lenovo ThinkPad T400 and Lenovo ThinkPad X200, can cause kernel panic.
kernel component
On a system configured with an HP Smart Array controller, during the kdump process, the capturing kernel can become unresponsive and the following error message is logged: 
NMI: IOCK error (debug interrupt?)
As a workaround, the system can be configured by blacklisting the hpsa module in a configuration file such as /etc/modules.d/blacklist.conf, and specifying the disk_timeout option so that saving the vmcore over the network is possible.
kernel component
Memory Type Range Register (MTRR) setup on some hyperthreaded machines may be incorrect following a suspend/resume cycle. This can cause graphics performance (specifically, scrolling) to slow considerably after a suspend/resume cycle.
To work around this issue, disable and then re-enable the hyperthreaded sibling CPUs around suspend/resume, for example: 
#!/bin/sh
# Disable hyper-threading processor cores on suspend and hibernate, re-enable
# on resume.
# This file goes into /etc/pm/sleep.d/

case $1 in
        hibernate|suspend)
                echo 0 > /sys/devices/system/cpu/cpu1/online
                echo 0 > /sys/devices/system/cpu/cpu3/online
                ;;

        thaw|resume)
                echo 1 > /sys/devices/system/cpu/cpu1/online
                echo 1 > /sys/devices/system/cpu/cpu3/online
                ;;
esac
kernel component
In Red Hat Enterprise Linux 6.2, nmi_watchdog registers with the perf subsystem. Consequently, during boot, the perf subsystem grabs control of the performance counter registers, blocking OProfile from working. To resolve this, either boot with the nmi_watchdog=0 kernel parameter set, or run the following command to disable it at run time: 
echo 0 > /proc/sys/kernel/nmi_watchdog
To re-enable nmi-watchdog, use the following command 
echo 1 > /proc/sys/kernel/nmi_watchdog
kernel component, BZ#603911
Due to the way ftrace works when modifying the code during start-up, the NMI watchdog causes too much noise and ftrace can not find a quiet period to instrument the code. Consequently, machines with more than 512 CPUs will encounter issues with the NMI watchdog. Such issues will return error messages similar to BUG: NMI Watchdog detected LOCKUP and have either ftrace_modify_code or ipi_handler in the backtrace. To work around this issue, disable NMI watchdog by setting the nmi_watchdog=0 kernel parameter, or using the following command at run time: 
echo 0 > /proc/sys/kernel/nmi_watchdog
kernel component
On 64-bit POWER systems the EHEA NIC driver will fail when attempting to dump a vmcore via NFS. To work around this issue, utilize other kdump facilities, for example dumping to the local file system, or dumping over SSH.
kernel component, BZ#587909
A BIOS emulated floppy disk might cause the installation or kernel boot process to hang. To avoid this, disable emulated floppy disk support in the BIOS.
kernel component
The preferred method to enable nmi_watchdog on 32-bit x86 systems is to use either nmi_watchdog=2 or nmi_watchdog=lapic parameters. The parameter nmi_watchdog=1 is not supported.
kernel component
The kernel parameter, pci=noioapicquirk, is required when installing the 32-bit variant of Red Hat Enterprise Linux 6 on HP xw9300 workstations. Note that the parameter change is not required when installing the 64-bit variant.