.TH RTP 2
.UC
.SH NAME
rtp \- make/unmake a real time process
.SH SYNOPSIS
.B rtp(flag)
.SH DESCRIPTION
.I Rtp
changes the notion of the current process from that of a normal
UNIX process to that of a ``real time'' process.  A real time process
does not compete for system resources in the normal manner; instead,
a real time process is considered locked into physical memory
by the swap scheduler and
receives exclusive use of the central processor
from the process scheduler
whenever the real time process is in a executable state.
Furthermore, other processes which
previously were non-preemptable but had the potential of consuming
relatively large amounts of cpu time are made preemptable by
.I rtp.
.PP
It is the responsibility of the real time process to see to it that
use of the cpu is relinquished often enough and long enough for
other normal UNIX processes to run.
For this reason only the
super-user
or members of group 0
are allowed to change the mode of a process by
.I rtp.
.PP
The
.I flag
argument is set to a non-zero value to make a normal process into
a real time process.
There can be only one real time process active at any moment.
.SH ERRORS
.I Rtp
will fail if:
.TP 20
[EPERM]
The process's effective user ID is not the super-user and the process's
effective group ID is nonzero.
.TP 20
[EBUSY]
A real time process already exists.
.SH "SEE ALSO"
lock(2), nice(2), renice(2)
.SH ASSEMBLER
(rtp = 49.)
.br
(flag in r0)
.br
.B sys rtp
.SH AUTHOR
Thomas Ferrin, University of California, San Francisco