Hi! These two patches are the result of Thomas pestering me with migrate_disable() patches for upstream. The first one is a cleanup/fix for the existing balance_callback machinery. The second (ab)uses the context_switch() tail invocation of balance_callbacks() to push away 'undesirables' during CPU hotplug after we've marked the CPU as !active.
With this in place, Thomas can do his horrible migrate_disable() thing ;-)
