/*
* uvm_emap_update: update global emap generation number for current CPU.
*
* Function is called by MD code (eg. pmap) to take advantage of TLB flushes
* initiated for other reasons, that sync the emap as a side effect. Note
* update should be performed before the actual TLB flush, to avoid race
* with newly generated number.
*
* => can be called from IPI handler, therefore function must be safe.
* => should be called _after_ TLB flush.
* => emap generation number should be taken _before_ TLB flush.
* => must be called with preemption disabled.
*/