a9545eede4
Add an idletime user group that allows non-root users to run processes with idle scheduling priority. Privileges are granted by a MAC policy in the mac_priority module. For this purpose, the kernel privilege PRIV_SCHED_IDPRIO was added to sys/priv.h (kernel module ABI change). Deprecate the system wide sysctl(8) knob security.bsd.unprivileged_idprio which lets any user run idle priority processes, regardless of context. While the knob is still working, it is marked as deprecated in the description and in the man pages. MFC after: 2 weeks Differential revision: https://reviews.freebsd.org/D33338
207 lines
6.2 KiB
Groff
207 lines
6.2 KiB
Groff
.\"-
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.\" 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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.\" Copyright (c) 2011 Xin LI <delphij@FreeBSD.org>
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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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.\"
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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 December 8, 2021
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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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.Nm rtprio_thread
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.Nd examine or modify 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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.Ft int
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.Fn rtprio_thread "int function" "lwpid_t lwpid" "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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or the calling thread.
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The
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.Fn rtprio_thread
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system call
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is used to lookup or change the realtime or idle priority of a thread.
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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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.Pp
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For the
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.Fn rtprio
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system call,
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the
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.Fa pid
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argument
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specifies the process to operate on,
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0 for the calling thread.
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When
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.Fa pid
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is non-zero,
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the system call reports the highest priority in the process,
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or sets all threads' priority in the process,
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depending on value of the
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.Fa function
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argument.
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.Pp
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For the
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.Fn rtprio_thread
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system call,
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the
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.Fa lwpid
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specifies the thread to operate on,
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0 for the calling thread.
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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
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.Pq 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
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.Fn fork
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and
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.Fn exec .
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.Pp
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A realtime thread can only be preempted by a thread of equal or
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higher priority, or by an interrupt; idle priority threads will run only
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when no other real/normal priority thread is runnable.
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Higher real/idle priority threads
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preempt lower real/idle priority threads.
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Threads of equal real/idle priority are run round-robin.
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.Sh RETURN VALUES
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.Rv -std rtprio rtprio_thread
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.Sh ERRORS
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The
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.Fn rtprio
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and
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.Fn rtprio_thread
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system calls
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will fail if:
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.Bl -tag -width Er
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.It Bq Er EFAULT
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The rtp pointer passed to
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.Fn rtprio
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or
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.Fn rtprio_thread
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was invalid.
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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 thread is not allowed to set the priority.
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Only
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root is allowed to change the realtime or idle priority of any thread.
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Exceptional privileges can be granted through the
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.Xr mac_priority 4
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policy and the realtime and idletime user groups.
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The
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.Xr sysctl 8
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variable
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.Va security.bsd.unprivileged_idprio
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is deprecated.
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If set to non-zero, it lets any user change the idle priority of threads
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they own.
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.It Bq Er ESRCH
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The specified process or thread was not found or visible.
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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 mac_priority 4 ,
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.Xr renice 8 ,
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.Xr p_cansee 9
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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 Mt 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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The
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.Fn rtprio_thread
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system call was implemented by
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.An David Xu .
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