5.14. kernel

Attempting to boot the x86 kernel on AMD Magny-Cours systems may result in a kernel panic. A fix will be made available in Red Hat Enterprise Linux 5.5 z-stream updates. To work around this issue, install the x86 variant of Red Hat Enterprise Linux 5.4 and upgrade to Red Hat Enterprise Linux 5.5.z. (BZ#575799)

A kernel panic may be triggered by the lpfc driver when multiple Emulex OneConnect Universal Converged Network Adapter initiators are included in the same Storage Area Network (SAN) zone. Typically, this kernel panic will present after a cable is pulled or one of the systems is rebooted. To work around this issue, configure the SAN to use single initiator zoning. (BZ#574858)

Systems containing AMD64 or Intel64 based hardware that use the x86 PAE kernel variant may fail to perform a core dump. AMD64 or Intel64 based hardware is able to handle more than 64GB of RAM, but the PAE kernel is strictly limited to 64GB. kexec-tools is aware of memory over the 64GB limit, but is unable to access it or produce a vmcore file. (BZ#559928)

Hot-adding memory is not a supported action in Red Hat Enterprise Linux 5.5. However, with Nehalem-EX processors, hot-adding memory must be performed at the same time as hot-adding a CPU. Consequently, hot-adding a CPU is also not a supported action on Nehalem-EX processors. (BZ#515298)

If a Huawei USB modem is unplugged from a system, the device may not be detected when it is attached again. To work around this issue, the usbserial and usb-storage driver modules need to be reloaded, allowing the system to detect the device. Alternatively, the if the system is rebooted, the modem will be detected also. (BZ#517454)

Memory on-line is not currently supported with the Boxboro-EX platform. (BZ#515299)

Unloading a PF (SR-IOV Physical function) driver from a host when a guest is using a VF (virtual function) from that device can cause a host crash. A PF driver for an SR-IOV device should not be unloaded until after all guest virtual machines with assigned VFs from that SR-IOV device have terminated. (BZ#514360)

Under some circumstances, the sky2 driver may hang, returning the following error message:

sky2 eth<N>: receiver hang detected

Currently, the only work around to make the device online again is to reboot the system. This bug will be repaired in an upcoming update to Red Hat Enterprise Linux 5.4. (BZ#509891, BZ#517976)

Data corruption on NFS filesystems might be encountered on network adapters without support for error-correcting code (ECC) memory that also have TCP segmentation offloading (TSO) enabled in the driver. Note: data that might be corrupted by the sender still passes the checksum performed by the IP stack of the receiving machine A possible work around to this issue is to disable TSO on network adapters that do not support ECC memory. BZ#504811

After installation, a System z machine with a large number of memory and CPUs (e.g. 16 CPU's and 200GB of memory) might may fail to IPL. To work around this issue, change the line

ramdisk=/boot/initrd-2.6.18-<kernel-version-number>.el5.img

to

ramdisk=/boot/initrd-2.6.18-<kernel-version-number>.el5.img,0x02000000

The command zipl -V should now show 0x02000000 as the starting address for the inital RAM disk (initrd). Stop the logigal partiton (LPAR), and then manually increase the the storage size of the LPAR.

On certain hardware configurations the kernel may panic when the Broadcom iSCSI offload driver (bnx2i.ko and cnic.ko) is loaded. To work around this do not manually load the bnx2i or cnic modules, and temporarily disable the iscsi service from starting. To disable the iscsi service, run

chkconfig --del iscsi
chkconfig --del iscsid

On the first boot of your system, the iscsi service may start automatically. To bypass this, during bootup, enter interactive start up and stop the iscsi service from starting.

In Red Hat Enterprise Linux 5, invoking the kernel system call "setpriority()" with a "which" parameter of type "PRIO_PROCESS" does not set the priority of child threads. (BZ#472251)

Physical CPUs cannot be safely placed offline or online when the 'kvm_intel' or 'kvm_amd' module is loaded. This precludes physical CPU offline and online operations when KVM guests that utilize processor virtualization support are running. It also precludes physical CPU offline and online operations without KVM guests running when the 'kvm_intel' or 'kvm_amd' module is simply loaded and not being used.

If the kmod-kvm package is installed, the 'kvm_intel' or 'kvm_amd' module automatically loads during boot on some systems. If a physical CPU is placed offline while the 'kvm_intel' or 'kvm_amd' module is loaded a subsequent attempt to online that CPU may fail with an I/O error.

To work around this issue, unload the 'kvm_intel' or 'kvm_amd' before performing physical CPU hot-plug operations. It may be necessary to shut down KVM guests before the 'kvm_intel' or 'kvm_amd' will successfully unload.

For example, to offline a physical CPU 6 on an Intel based system:

# rmmod kvm_intel
# echo 0 > /sys/devices/system/cpu/cpu6/online
# modprobe kvm_intel

(BZ#515557)

A change to the cciss driver in Red Hat Enterprise Linux 5.4 made it incompatible with the "echo disk > /sys/power/state" suspend-to-disk operation. Consequently, the system will not suspend properly, returning messages such as:

Stopping tasks:
======================================================================
 stopping tasks timed out after 20 seconds (1 tasks remaining):
  cciss_scan00
Restarting tasks...<6> Strange, cciss_scan00 not stopped
 done

(BZ#513472)

The kernel is unable to properly detect whether there is media present in a CD-ROM drive during kickstart installs. The function to check the presence of media incorrectly interprets the "logical unit is becoming ready" sense, returning that the drive is ready when it is not. To work around this issue, wait several seconds between inserting a CD and asking the installer (anaconda) to refresh the CD. (BZ#510632)

Applications attempting to malloc memory approximately larger than the size of the physical memory on the node on a NUMA system may hang or appear to stall. This issue may occur on a NUMA system where the remote memory distance, as defined in SLIT, is greater than 20 and RAM based filesystem like tmpfs or ramfs is mounted.

To work around this issue, unmount all RAM based filesystems (i.e. tmpfs or ramfs). If unmounting the RAM based filesystems is not possible, modify the application to allocate lesser memory. Finally, if modifying the application is not possible, disable NUMA memory reclaim by running:

sysctl vm.zone_reclaim_mode=0

(BZ#507360)

Configuring IRQ SMP affinity has no effect on some devices that use message signalled interrupts (MSI) with no MSI per-vector masking capability. Examples of such devices include Broadcom NetXtreme Ethernet devices that use the bnx2 driver.

If you need to configure IRQ affinity for such a device, disable MSI by creating a file in /etc/modprobe.d/ containing the following line:

options bnx2 disable_msi=1

Alternatively, you can disable MSI completely using the kernel boot parameter pci=nomsi. (BZ#432451)

The smartctl tool cannot properly read SMART parameters from SATA devices. (BZ#429606)

IBM T60 laptops will power off completely when suspended and plugged into a docking station. To avoid this, boot the system with the argument acpi_sleep=s3_bios. (BZ#439006)

The QLogic iSCSI Expansion Card for the IBM Bladecenter provides both ethernet and iSCSI functions. Some parts on the card are shared by both functions. However, the current qla3xxx and qla4xxx drivers support ethernet and iSCSI functions individually. Both drivers do not support the use of ethernet and iSCSI functions simultaneously.

Because of this limitation, successive resets (via consecutive ifdown/ifup commands) may hang the device. To avoid this, allow a 10-second interval after an ifup before issuing an ifdown. Also, allow the same 10-second interval after an ifdown before issuing an ifup. This interval allows ample time to stabilize and re-initialize all functions when an ifup is issued. (BZ#276891)

Laptops equipped with the Cisco Aironet MPI-350 wireless may hang trying to get a DHCP address during any network-based installation using the wired ethernet port.

To work around this, use local media for your installation. Alternatively, you can disable the wireless card in the laptop BIOS prior to installation (you can re-enable the wireless card after completing the installation). (BZ#213262)

Hardware testing for the Mellanox MT25204 has revealed that an internal error occurs under certain high-load conditions. When the ib_mthca driver reports a catastrophic error on this hardware, it is usually related to an insufficient completion queue depth relative to the number of outstanding work requests generated by the user application.

Although the driver will reset the hardware and recover from such an event, all existing connections at the time of the error will be lost. This generally results in a segmentation fault in the user application. Further, if opensm is running at the time the error occurs, then you need to manually restart it in order to resume proper operation. (BZ#251934)

The IBM T41 laptop model does not enter Suspend Mode properly; as such, Suspend Mode will still consume battery life as normal. This is because Red Hat Enterprise Linux 5 does not yet include the radeonfb module.

To work around this, add a script named hal-system-power-suspend to /usr/share/hal/scripts/ containing the following lines:

	
chvt 1
radeontool light off
radeontool dac off

This script will ensure that the IBM T41 laptop enters Suspend Mode properly. To ensure that the system resumes normal operations properly, add the script restore-after-standby to the same directory as well, containing the following lines:

	
radeontool dac on
radeontool light on
chvt 7

(BZ#227496)

If the edac module is loaded, BIOS memory reporting will not work. This is because the edac module clears the register that the BIOS uses for reporting memory errors.

The current Red Hat Enterprise Linux Driver Update Model instructs the kernel to load all available modules (including the edac module) by default. If you wish to ensure BIOS memory reporting on your system, you need to manually blacklist the edac modules. To do so, add the following lines to /etc/modprobe.conf:

	
blacklist edac_mc
blacklist i5000_edac
blacklist i3000_edac
blacklist e752x_edac

(BZ#441329)

Due to outstanding driver issues with hardware encryption acceleration, users of Intel WiFi Link 4965, 5100, 5150, 5300, and 5350 wireless cards are advised to disable hardware accelerated encryption using module parameters. Failure to do so may result in the inability to connect to Wired Equivalent Privacy (WEP) protected wireless networks after connecting to WiFi Protected Access (WPA) protected wireless networks.

To do so, add the following options to /etc/modprobe.conf:

alias wlan0 iwlagn
options iwlagn swcrypto50=1 swcrypto=1

(where wlan0 is the default interface name of the first Intel WiFi Link device)

(BZ#468967)

The size of the PPC kernel image is too large for OpenFirmware to support. Consequently, network booting will fail, resulting in the following error message:

Please wait, loading kernel...
/pci@8000000f8000000/ide@4,1/disk@0:2,vmlinux-anaconda: No such file or directory
boot:

To work around this:

(BZ#462663)