The itimerfix function checks that the value in tv is valid (0 ≤ tv->tv_sec && 0 ≤ tv->tv_usec < 1000000), and that the total time represented is at least one tick, or zero.
If the total represented time is nonzero and smaller than tick, it is adjusted to exactly one tick.
RETURN VALUES
itimerfix returns 0 on success or EINVAL if tv is invalid.