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: src/lib/libc/sys/rtprio.2,v 1.13.2.9 2001/12/14 18:34:01 ru Exp $ 31.\" 32.Dd December 14, 2007 33.Dt RTPRIO 2 34.Os 35.Sh NAME 36.Nm rtprio , 37.Nm lwp_rtprio 38.Nd examine or modify a process/lwp realtime or idle priority 39.Sh LIBRARY 40.Lb libc 41.Sh SYNOPSIS 42.In sys/types.h 43.In sys/rtprio.h 44.Ft int 45.Fn rtprio "int function" "pid_t pid" "struct rtprio *rtp" 46.Ft int 47.Fn lwp_rtprio "int function" "pid_t pid" "lwpid_t tid" "struct rtprio *rtp" 48.Sh DESCRIPTION 49.Fn rtprio 50is used to lookup or change the realtime or idle priority of a process. 51.Pp 52.Fa function 53specifies the operation to be performed. 54.Dv RTP_LOOKUP 55to lookup the current priority, and 56.Dv RTP_SET 57to set the priority. 58.Fa pid 59specifies the process to be used, 0 for the current process. 60.Pp 61.Fa *rtp 62is a pointer to a 63.Vt struct rtprio 64which is used to specify the priority and priority type. 65This structure has the following form: 66.Bd -literal 67struct rtprio { 68 u_short type; 69 u_short prio; 70}; 71.Ed 72.Pp 73The value of the 74.Nm type 75field may be 76.Dv RTP_PRIO_REALTIME 77for realtime priorities, 78.Dv RTP_PRIO_NORMAL 79for normal priorities, and 80.Dv RTP_PRIO_IDLE 81for idle priorities. 82The priority specified by the 83.Nm prio 84field ranges between 0 and 85.Dv RTP_PRIO_MAX (usually 31) . 860 is the highest possible priority. 87.Pp 88Realtime and idle priority is inherited through 89.Fn fork 90and 91.Fn exec . 92.Pp 93A realtime process can only be preempted by a process of equal or 94higher priority, or by an interrupt; idle priority processes will run only 95when no other real/normal priority process is runnable. 96Higher real/idle priority processes 97preempt lower real/idle priority processes. 98Processes of equal real/idle priority are run round-robin. 99.Pp 100The 101.Fn lwp_rtprio 102function is the lwp counterpart of 103.Fn rtprio . 104It takes one additional argument, 105.Fa tid , 106specifying the lwp to be used, -1 for the current lwp. 107.Sh RETURN VALUES 108.Rv -std rtprio lwp_rtprio 109.Sh ERRORS 110.Fn rtprio 111and 112.Fn lwp_rtprio 113will fail if 114.Bl -tag -width Er 115.It Bq Er EINVAL 116The specified 117.Fa prio 118was out of range. 119.It Bq Er EPERM 120The calling process is not allowed to set the realtime priority. 121Only 122root is allowed to change the realtime priority of any process, and non-root 123may only change the idle priority of the current process. 124.It Bq Er ESRCH 125The specified process was not found. 126.El 127.Sh SEE ALSO 128.Xr nice 1 , 129.Xr ps 1 , 130.Xr rtprio 1 , 131.Xr setpriority 2 , 132.Xr nice 3 , 133.Xr renice 8 134.Sh AUTHORS 135.An -nosplit 136The original author was 137.An Henrik Vestergaard Draboel Aq Mt hvd@terry.ping.dk . 138This implementation was substantially rewritten by 139.An David Greenman . 140