idle - make process 0 idle
idle is an internal system call used during bootstrap. It
marks the process's pages as swappable, lowers its priority,
and enters the main scheduling loop. idle never returns.
Only process 0 may call idle. Any user process, even a pro-
cess with super-user permission, will receive EPERM.
idle never returns for process 0, and always returns -1 for
a user process.
EPERM Always, for a user process.
This function is Linux-specific, and should not be used in
programs intended to be portable.