Red Hat ENTERPRISE LINUX 5.4 - TECHNICAL NOTES Manual page 318

Chapter 4. Known Issues
• 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.
• 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
(BZ#213262)
installation).
• 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.
• If your system uses the TSC timer, the gettimeofday system call may move backwards. This is
because of an overflow issue that causes the TSC timer to jump forward significantly in some cases;
when this occurs, the TSC timer will correct itself, but will ultimately register a movement backwards
in time.
This issue is particularly critical for time-sensitive systems, such as those used for transaction
systems and databases. As such, if your system needs precision timing, Red Hat strongly
recommends that you set the kernel to use another timer (for example, HPET).
• 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
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(BZ#251934)
(BZ#276891)
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(BZ#443435)
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