Instead of relying on preemption disabled rt protects the per cpu data
structures with per cpu locks.

This patch contains fixes from 
     Andi Kleen <ak@suse.de>
     Peter Zijlstra <a.p.zijlstra@chello.nl>
     Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>