void
set_next_timeout() {
// There is a very strange bug,
// if comment the `printf` line below
// the timer will not work.
// this bug seems to disappear automatically
// printf("");
sbi_set_timer(r_time() + INTERVAL);
}
struct tms {
uint64 utime; // user time
uint64 stime; // system time
uint64 cutime; // user time of children
uint64 cstime; // system time of children
};