Xinu7/man/man2/chprio.2

.TH CHPRIO 2
.SH NAME
chprio \- change the priority of a process
.SH SYNOPSIS
.B int
.B chprio(pid,newprio)
.nf
.B int pid;
.B int newprio;
.fi
.SH DESCRIPTION
.I Chprio
changes the scheduling priority of process
.I pid
to
.I newprio.
Priorities are positive integers.
At any instant, the highest priority process  that is ready
will be running.
A set of processes with equal priority is scheduled round-robin.
.PP
If the new priority is invalid, or the process id is invalid
.I chprio
returns SYSERR.
Otherwise, it returns the old process priority.
It is forbidden to change the priority of the null process, which
always remains zero.
.SH SEE ALSO
create(2), getprio(2), resume(2)
.SH BUGS
Because
.I chprio
changes priorities without rearranging processes on the ready list,
it should only be used on waiting, sleeping, suspended, or current
processes.