.\" Copyright (c) 2007 The DragonFly Project.  All rights reserved.
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.\" by Matthew Dillon <dillon@backplane.com>
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.\" $DragonFly: src/lib/libc/sys/usched_set.2,v 1.4 2007/12/23 15:31:28 swildner Exp $
.\"
.Dd February 26, 2009
.Dt USCHED_SET 2
.Os
.Sh NAME
.Nm usched_set
.Nd setting up a proc's usched
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/types.h
.In sys/usched.h
.Ft int
.Fn usched_set "pid_t pid" "int cmd" "void *data" "int bytes"
.Sh DESCRIPTION
The
.Fn usched_set
function is used to perform several user scheduler tasks.
These tasks include: setting the user scheduler, assigning an LWP to a
specific CPU, adding a CPU to the available CPUs for an LWP,
and removing a CPU from the list of available CPUs for an LWP.
The
.Fn usched_set
function requires superuser privileges for all commands except
.Dv USCHED_GET_CPU .
.Pp
The
.Fa cmd
argument specifies the action for
.Fn usched_set
to take.
.Dv USCHED_SET_SCHEDULER
sets the user scheduler where
.Fa data
is a
.Vt char *
that contains the name of the user scheduler.
.Dv USCHED_SET_CPU
assigns the LWP to the cpuid pointed to by
.Fa data .
.Dv USCHED_GET_CPU
copies the LWP's CPU ID to the cpuid pointed to by
.Fa data .
.Dv USCHED_ADD_CPU
adds the cpuid specified by
.Fa data
to the list of available CPUs for the LWP.
.Dv USCHED_DEL_CPU
removes the cpuid specified by
.Fa data
from the list of available CPUs for the LWP.
.Sh RETURN VALUES
.Rv -std
.Sh ERRORS
The function will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The user scheduler to set is not in the list of available user schedulers.
The
.Fa bytes
argument is not the correct size
.Vt ( int )
for a cpuid.
The specified cpuid is not set in
.Va smp_active_mask .
.Fa Cmd
contains an unknown value.
.It Bq Er EFBIG
The specified cpuid is not a valid cpuid for the system.
.It Bq Er EPERM
Deleting the specified cpuid leaves the LWP without a CPU to run on.
.El
.\".Sh SEE ALSO
.Sh HISTORY
The
.Fn usched_set
function call was added in
.Dx 1.9 .
.Sh AUTHORS
.An -nosplit
.Fn Usched_set
was written by
.An Matt Dillon .
This manual page was written by
.An Joe Talbott .