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.Sh NAME 35.Nm rtprio 36.Nd examine or modify a process realtime or idle priority 37.Sh SYNOPSIS 38.Fd #include <sys/types.h> 39.Fd #include <sys/rtprio.h> 40.Ft int 41.Fn rtprio "int function" "pid_t pid" "struct rtprio *rtp" 42.Sh DESCRIPTION 43.Fn rtprio 44is used to lookup or change the realtime or idle priority of a process. 45 46.Fa function 47specifies the operation to be performed. RTP_LOOKUP to lookup the current priority, 48and RTP_SET to set the priority. 49.Fa pid 50specifies the process to be used, 0 for the current process. 51 52.Fa *rtp 53is a pointer to a struct rtprio which is used to specify the priority and priority type. 54This structure has the following form: 55.Bd -literal 56struct rtprio { 57 u_short type; 58 u_short prio; 59}; 60.Ed 61.Pp 62The value of the 63.Nm type 64field may be RTP_PRIO_REALTIME for realtime priorities, 65RTP_PRIO_NORMAL for normal priorities, and RTP_PRIO_IDLE for idle priorities. 66The priority specified by the 67.Nm prio 68field ranges between 0 and 69.Dv RTP_PRIO_MAX (usually 31) . 700 is the highest possible priority. 71 72Realtime and idle priority is inherited through fork() and exec(). 73 74A realtime process can only be preempted by a process of equal or 75higher priority, or by an interrupt; idle priority processes will run only 76when no other real/normal priority process is runnable. Higher real/idle priority processes 77preempt lower real/idle priority processes. Processes of equal real/idle priority are run round-robin. 78.Sh RETURN VALUES 79.Fn rtprio 80will return 0 for success and -1 for all errors. The global variable 81.Va errno 82will be set to indicate the error. 83.Sh ERRORS 84.Fn rtprio 85will fail if 86.Bl -tag -width Er 87.It Bq Er EINVAL 88The specified 89.Fa prio 90was out of range. 91.It Bq Er EPERM 92The calling process is not allowed to set the realtime priority. Only 93root is allowed to change the realtime priority of any process, and non-root 94may only change the idle priority of the current process. 95.It Bq Er ESRCH 96The specified process was not found. 97.Sh AUTHORS 98The original author was 99.An Henrik Vestergaard Draboel Aq [email protected] . 100This implementation in 101.Fx 102was substantially rewritten by 103.An David Greenman . 104.Sh SEE ALSO 105.Xr nice 1 , 106.Xr ps 1 , 107.Xr rtprio 1 , 108.Xr setpriority 2 , 109.Xr nice 3 , 110.Xr renice 8 111