A 2.6.9-ac1 kernel would be

A.
someone’s patch to a stable kernel.

B.
someone’s patch to an unstable kernel.

C.
a stable kernel.

D.
an unstable kernel.

E.
an alpha kernel.

Explanation:
This file is the patch file for security bugs of 2.6.9 version kernel.
This bug fixes the following bugs:
Security Fixes o Set VMJO on areas that are temporarily marked PageReserved (Serious bug)
o Lock ide-proc against driver unload Bug Fixes Working IDE locking And a great deal of review
by Bartiomiejo Handle E7xxx boxes with USB legacy flaws
Functionality
o Allow booting with “irqpoN” or “irqfixup”on systems with broken IRQ tables. oSupportforsetuid
core dumping in some environments (off by default) o Support for drives that don’t report geometry
o IT8212 support (raid and passthrough)
o Allow IDE to grab all unknown generic IDE devices (boot with “all-generic-ide”)o Restore PWC
driver
o Small pending tty clean-up to moxa
o Put VIA Velocity ™ adapters under gigabit