1.\" Copyright (c) 1994, Henrik Vestergaard Draboel 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by Henrik Vestergaard Draboel. 15.\" 4. The name of the author may not be used to endorse or promote products 16.\" derived from this software without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" $FreeBSD$ 31.\" 32.Dd July 23, 1994 33.Dt RTPRIO 2 34.Os 35.Sh NAME 36.Nm rtprio 37.Nd examine or modify a process realtime or idle priority 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.Fd #include <sys/types.h> 42.Fd #include <sys/rtprio.h> 43.Ft int 44.Fn rtprio "int function" "pid_t pid" "struct rtprio *rtp" 45.Sh DESCRIPTION 46.Fn rtprio 47is used to lookup or change the realtime or idle priority of a process. 48.Pp 49.Fa function 50specifies the operation to be performed. 51RTP_LOOKUP to lookup the current priority, 52and RTP_SET to set the priority. 53.Fa pid 54specifies the process to be used, 0 for the current process. 55.Pp 56.Fa *rtp 57is a pointer to a struct rtprio which is used to specify the priority and priority type. 58This structure has the following form: 59.Bd -literal 60struct rtprio { 61 u_short type; 62 u_short prio; 63}; 64.Ed 65.Pp 66The value of the 67.Nm type 68field may be RTP_PRIO_REALTIME for realtime priorities, 69RTP_PRIO_NORMAL for normal priorities, and RTP_PRIO_IDLE for idle priorities. 70The priority specified by the 71.Nm prio 72field ranges between 0 and 73.Dv RTP_PRIO_MAX (usually 31) . 740 is the highest possible priority. 75.Pp 76Realtime and idle priority is inherited through fork() and exec(). 77.Pp 78A realtime process can only be preempted by a process of equal or 79higher priority, or by an interrupt; idle priority processes will run only 80when no other real/normal priority process is runnable. 81Higher real/idle priority processes 82preempt lower real/idle priority processes. 83Processes of equal real/idle priority are run round-robin. 84.Sh RETURN VALUES 85.Fn rtprio 86will return 0 for success and -1 for all errors. 87The global variable 88.Va errno 89will be set to indicate the error. 90.Sh ERRORS 91.Fn rtprio 92will fail if 93.Bl -tag -width Er 94.It Bq Er EINVAL 95The specified 96.Fa prio 97was out of range. 98.It Bq Er EPERM 99The calling process is not allowed to set the realtime priority. 100Only 101root is allowed to change the realtime priority of any process, and non-root 102may only change the idle priority of the current process. 103.It Bq Er ESRCH 104The specified process was not found. 105.El 106.Sh AUTHORS 107.An -nosplit 108The original author was 109.An Henrik Vestergaard Draboel Aq [email protected] . 110This implementation in 111.Fx 112was substantially rewritten by 113.An David Greenman . 114.Sh SEE ALSO 115.Xr nice 1 , 116.Xr ps 1 , 117.Xr rtprio 1 , 118.Xr setpriority 2 , 119.Xr nice 3 , 120.Xr renice 8 121