kernel bug fix update

Updated kernel packages that fix various bugs are now available for Red
Hat Enterprise Linux 4.

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

These updated packages fix the following bugs:

* dm-raid1 did not have queue unplugging. This introduced a 3ms delay
between each request. As a consequence synchronous writes to dm-raid1 were
only one tenth as fast as writes to dm-linear. This update adds the unplug
call (to kmirrord).

* the portmap routines wrote results straight to the cl_port field of the
RPC client. In some circumstances, this structure could be marked as free
before all outstanding portmap calls succeeded. When an RPC client was
destroyed while it still had an active portmap child task, memory
corruption was possible. This update changes the portmap routine. It now
allocates a new "rpc_pmap_result" struct and the parent task now copies the
result out of that structure. As well, this new struct is managed with a
kref, which prevents it from being freed until every user is finished with
it.

* a regression was found in the kernel Advanced Programmable Interrupt
Controllers (APIC) code. On systems with sixteen or more cores, the mode
was wrongly set to "clustered" instead of "physflat". This did not result
in kernel panics but did result in underutilization of some CPUs on such
systems and consequent reduced system performance. The mode is now set
correctly on systems with sixteen or more cores.

* on x86-based systems, walking through deeply nested symlinks could cause
a kernel stack overflow. In this updated kernel, the memory used by the
function which precipitated the stack overflow has been reduced, especially
when traversing deeply nested symlinks.

* a regression was found in the Advanced Linux Sound Architecture (ALSA)
subsystem: a parameter sanity check was missing. This sent the kernel into
an infinite loop when 32-bit sounds were played on 64-bit systems. The
parameter sanity check is present in this update.

All Red Hat Enterprise Linux 4 users are advised to upgrade to these
updated packages, which contain backported patches to resolve these issues.

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

This update is available via Red Hat Network. Details on how to use
the Red Hat Network to apply this update are available at
http://kbase.redhat.com/faq/FAQ_58_10188

457229 - [CRM 1790680] Poor LVM mirroring performance
457231 - memory corruption due to portmap call succeeding after parent rpc_clnt has been freed
458782 - APIC mode is wrong when system with 16cores or above
460637 - [RHEL4][PATCH] kernel stack overflow at ia32 AS4 / stack usage of link_path_walk() ?
461896 - [RHEL 4.7] U7 kernel locks up when 32-bit alsa is played on x86_64