1 .\" Copyright (c) 1994, Henrik Vestergaard Draboel
2 .\" All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
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14 .\" This product includes software developed by Henrik Vestergaard Draboel.
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30 .\" $FreeBSD: src/lib/libc/sys/rtprio.2,v 1.13.2.9 2001/12/14 18:34:01 ru Exp $
31 .\" $DragonFly: src/lib/libc/sys/rtprio.2,v 1.2 2003/06/17 04:26:47 dillon Exp $
38 .Nd examine or modify a process realtime or idle priority
45 .Fn rtprio "int function" "pid_t pid" "struct rtprio *rtp"
48 is used to lookup or change the realtime or idle priority of a process.
51 specifies the operation to be performed.
52 RTP_LOOKUP to lookup the current priority,
53 and RTP_SET to set the priority.
55 specifies the process to be used, 0 for the current process.
58 is a pointer to a struct rtprio which is used to specify the priority and priority type.
59 This structure has the following form:
69 field may be RTP_PRIO_REALTIME for realtime priorities,
70 RTP_PRIO_NORMAL for normal priorities, and RTP_PRIO_IDLE for idle priorities.
71 The priority specified by the
73 field ranges between 0 and
74 .Dv RTP_PRIO_MAX (usually 31) .
75 0 is the highest possible priority.
77 Realtime and idle priority is inherited through fork() and exec().
79 A realtime process can only be preempted by a process of equal or
80 higher priority, or by an interrupt; idle priority processes will run only
81 when no other real/normal priority process is runnable.
82 Higher real/idle priority processes
83 preempt lower real/idle priority processes.
84 Processes of equal real/idle priority are run round-robin.
96 The calling process is not allowed to set the realtime priority.
98 root is allowed to change the realtime priority of any process, and non-root
99 may only change the idle priority of the current process.
101 The specified process was not found.
105 The original author was
106 .An Henrik Vestergaard Draboel Aq hvd@terry.ping.dk .
107 This implementation in
109 was substantially rewritten by