callout_schedule
callout_schedule(&sc->sc_wd_ch, hz);
callout_schedule(&sc->sc_timer, sc->sc_ageinterval*hz);
int callout_schedule(struct callout *c, int _ticks);
callout_schedule(&dfs->nol_timer, oldest + NOL_TIMEOUT - now);
callout_schedule(&dfs->cac_timer, 0);
return (callout_schedule(&to->c, USEC_2_TICKS(usec)) ? 0 : 1);