[CVE-2012-1146] memcg unregister oops

[Andy Whitcroft]

CVE-2012-1146
	memcg unregisters events that were attached to the same eventfd

This issue was introduced for maverick.  Following this email is a
patch for maverick, maverick/ti-omap4, natty, natty/ti-omap4, oneiric,
and precise, this is a simple cherry-pick from the mainline fix.

Proposing for maverick, maverick/ti-omap4, natty, natty/ti-omap4, oneiric,
and precise.

-apw