USER_CLOCKEVENT
used_before = p->active[USER_CLOCKSOURCE] | p->active[USER_CLOCKEVENT];
used_before = p->active[USER_CLOCKSOURCE] | p->active[USER_CLOCKEVENT];
used_after = p->active[USER_CLOCKSOURCE] | p->active[USER_CLOCKEVENT];
em_sti_stop(p, USER_CLOCKEVENT);
em_sti_start(p, USER_CLOCKEVENT);