kernel bug fix update

Updated kernel packages that fix several bugs are now available for Red Hat
Enterprise Linux 5.

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

These updated packages addresses the following bugs:

* RHSA-2009-1106 included a fix for a rare race condition (BZ#486921). This
earlier race condition occurred if an application performed multiple
O_DIRECT reads per virtual memory page and also performed fork(2).
Unfortunately, the fix included with RHSA-2009-1106 introduced a new, very
small, race condition which presented if the system was swapping heavily or
heavily reproducing the conditions that were the cause of BZ#486921. With
this update, the parent pte is not set to writable if the src pte is
unmapped by the VM, preventing the race condition from occurring.
(BZ#507297)

* the copy_hugetlb_page_range() function assumed it was safe to drop the
source mm->page_table_lock before calling hugetlb_cow(). As a consequence a
kernel panic occurred when a particular multi-threaded application did
Direct IO on a HUGEPAGE-mapped file region and created new processes. With
this update, copy_hugetlb_page_range() calls hugetlb_cow() with the locks
held, ensuring the panic does not occur. (BZ#508030)

Red Hat Enterprise Linux 5 users are advised to upgrade to these updated
packages, which 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/docs/DOC-11259

507297 - Corruption on ext3/xfs with O_DIRECT and unaligned user buffers
508030 - [5.4][REG] The system panic occurs, when a file is accessed by multiple processes simultaneously.