Kernel - Red Hat ENTERPRISE LINUX 5.4 - TECHNICAL NOTES Manual

Chapter 4. Known Issues

4.13. kernel

The Kernel
• 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.
45
BZ#517976)
• 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.
• 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
47
(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:
298
44
(BZ#509891
,
46
(BZ#472251)