127 lines
3.9 KiB
Groff
127 lines
3.9 KiB
Groff
.\" Copyright (c) 1994, Henrik Vestergaard Draboel
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by Henrik Vestergaard Draboel.
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.\" 4. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd July 23, 1994
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.Dt RTPRIO 2
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.Os
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.Sh NAME
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.Nm rtprio
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.Nd examine or modify a process realtime or idle priority
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/types.h
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.In sys/rtprio.h
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.Ft int
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.Fn rtprio "int function" "pid_t pid" "struct rtprio *rtp"
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.Sh DESCRIPTION
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The
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.Fn rtprio
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system call
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is used to lookup or change the realtime or idle priority of a process.
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.Pp
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The
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.Fa function
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argument
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specifies the operation to be performed.
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RTP_LOOKUP to lookup the current priority,
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and RTP_SET to set the priority.
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The
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.Fa pid
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argument
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specifies the process to be used, 0 for the current process.
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.Pp
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The
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.Fa *rtp
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argument
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is a pointer to a struct rtprio which is used to specify the priority and priority type.
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This structure has the following form:
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.Bd -literal
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struct rtprio {
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u_short type;
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u_short prio;
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};
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.Ed
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.Pp
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The value of the
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.Va type
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field may be RTP_PRIO_REALTIME for realtime priorities,
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RTP_PRIO_NORMAL for normal priorities, and RTP_PRIO_IDLE for idle priorities.
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The priority specified by the
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.Va prio
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field ranges between 0 and
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.Dv RTP_PRIO_MAX (usually 31) .
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0 is the highest possible priority.
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.Pp
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Realtime and idle priority is inherited through fork() and exec().
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.Pp
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A realtime process can only be preempted by a process of equal or
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higher priority, or by an interrupt; idle priority processes will run only
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when no other real/normal priority process is runnable.
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Higher real/idle priority processes
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preempt lower real/idle priority processes.
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Processes of equal real/idle priority are run round-robin.
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.Sh RETURN VALUES
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.Rv -std rtprio
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.Sh ERRORS
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The
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.Fn rtprio
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system call
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will fail if
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The specified
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.Fa prio
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was out of range.
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.It Bq Er EPERM
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The calling process is not allowed to set the realtime priority.
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Only
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root is allowed to change the realtime priority of any process, and non-root
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may only change the idle priority of the current process.
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.It Bq Er ESRCH
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The specified process was not found.
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.El
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.Sh SEE ALSO
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.Xr nice 1 ,
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.Xr ps 1 ,
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.Xr rtprio 1 ,
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.Xr setpriority 2 ,
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.Xr nice 3 ,
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.Xr renice 8
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.Sh AUTHORS
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.An -nosplit
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The original author was
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.An Henrik Vestergaard Draboel Aq hvd@terry.ping.dk .
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This implementation in
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.Fx
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was substantially rewritten by
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.An David Greenman .
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