RHBA-2012:0496 - Bug Fix Advisory

Topic

Updated kernel-rt packages that fix several bugs are now available for Red Hat
Enterprise MRG 2.1.

Description

The kernel-rt packages contain the Linux kernel, the core of any Linux operating
system.

This update provides a build of the kernel-rt package for MRG 2.1, which is
layered on Red Hat Enterprise Linux 6.

This update fixes the following bugs:

• Previously, while working with an open file, the epoll kernel code was calling

poll operations of another open file without holding the file's lock.
Consequently, a deadlock in the code could occur when using the system console.
Now, an upstream patch to use the ep_poll_nested() function has been provided
and the system console now works correctly in the described scenario.
(BZ#675885)

• The i7core_edac code did multiple probes for the same hardware component. As a

consequence, boot time error message about the code being unable to create a
duplicate file in the /sys/devices/ directory was returned. With this update,
duplicate probe code has been removed and the error messages are no longer
returned in the described scenario. (BZ#773746)

• A previous Realtime work queue patch introduced a race conditions in the CPU

hotplug code. Consequently, the system could become unresponsive in this code.
This update reverts a few past updates to the work queue, which turned out to be
unnecessary, and the hangs no longer occur in the described scenario.
(BZ#787331)

• The CONFIG_CC_OPTIMIZE_FOR_SIZE configuration parameter, which was previously

introduced to MRG Realtime, caused the gcc compiler to produce code prone to
cache line bouncing. As a result, the kernel performance was decreased. This
update turns off this parameter, thus improving cache utilization and
performance. (BZ#796297)

• Previously, configuration files in MRG Realtime and Red Hat Enterprise Linux 6

were not synchronized regarding modules and built-ins. Consequently, the
mkinitrd daemon failed to find code that was part of a module in Red Hat
Enterprise Linux 6 but part of a built-in in MRG Realtime. Now, the
configuration files have been synchronized between these two products and
mkinitrd correctly finds and sets up kernel components such as kdump.
(BZ#804119, BZ#756631)

Users of the Realtime capabilities of Red Hat Enterprise MRG 2.1, which is
layered on Red Hat Enterprise Linux 6, are advised to upgrade to these updated
packages, which fix these bugs. Note that the system must be rebooted for this
update to take effect.

Solution

Before applying this update, make sure all previously-released errata
relevant to your system have been applied.

This update is available via the Red Hat Network. Details on how to
use the Red Hat Network to apply this update are available at
https://access.redhat.com/knowledge/articles/11258

Affected Products

• MRG Realtime 2 x86_64

Fixes

• BZ - 675885 - kernel: epoll: Prevent deadlock through unsafe ->f_op->poll() calls [mrg-2.1]
• BZ - 787331 - System hang running Java tests on 3.0.9-rt26.45.el6rt.x86_64 kernel
• BZ - 796297 - turn off CONFIG_CC_OPTIMIZE_FOR_SIZE

CVEs

• CVE-2011-1083

References

(none)