idle man page
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 process with superuser permission, will receive EPERM.
idle() never returns for process 0, and always returns -1 for a user process.
Always, for a user process.
Since Linux 2.3.13, this system call does not exist anymore.
This function is Linux-specific, and should not be used in programs intended to be portable.
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