Hmm, I didn't have the && when I first tested it and the script died on me after the autounmask-write.  This ideally shouldn't be something we do, it adds another potential point of interaction.  Unfortunately, I don't know of a way to automatically force a configuration change in Gentoo.  The downside of being rolling is that it becomes nigh impossible to anticipate this and make appropriate changes beforehand.  I'm not really sure how best to handle it.

Also, the reason why I didn't grep processor is that it doesn't compensate for hyperthreading.  The command that I have used is straight from the documentation.