Red Hat ENTERPRISE LINUX 5.5 - S 2010, Manual

Page: 326 / 470

Chapter 5. Known Issues
316
• 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).
(BZ#443435)
77
• 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)
78
• 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)
79
• 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.