I have just tried the realtime scheduler using `echo's of period, cost,
admit into the /proc/.../ctl of a test program.

In a 9fans posting I have seen another example where a real-time process
was created by opening /dev/realtime/clone. This usage pattern looks
interesting; a task that needs real-time conditions is not a real-time
task itself, but uses such a task to get the desired timing (this is at
least my understanding of it).

Apparently devrealtime.c has been removed from the kernel some time ago.
Likely this interface is obsolete, and the devproc one is current.

How would I use that properly? I suppose a task could write to its own
/proc/.../ctl to enable real-time mode. Is there an example available
similar to the devrealtime one?