175 lines
5.3 KiB
Groff
175 lines
5.3 KiB
Groff
.\" $FreeBSD$
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.\" Copyright (c) 1998 HD Associates, Inc.
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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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.\"
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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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.Dd March 12, 1998
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.Dt SCHED_SETPARAM 2
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.Os
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.Sh NAME
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.Nm sched_setparam ,
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.Nm sched_getparam
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.Nd set/get scheduling parameters
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sched.h
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.Ft int
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.Fn sched_setparam "pid_t pid" "const struct sched_param *param"
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.Ft int
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.Fn sched_getparam "pid_t pid" "struct sched_param *param"
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.Sh DESCRIPTION
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The
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.Fn sched_setparam
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system call sets the scheduling parameters of the process specified by
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.Fa pid
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to the values specified by the
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.Fa sched_param
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structure pointed to by
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.Fa param .
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The value of the
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.Fa sched_priority
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member in the
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.Fa param
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structure must be any integer within the inclusive priority range for
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the current scheduling policy of the process specified by
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.Fa pid .
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Higher numerical values for the priority represent higher priorities.
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.Pp
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In this implementation, if the value of
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.Fa pid
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is negative the system call will fail.
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.Pp
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If a process specified by
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.Fa pid
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exists and if the calling process has permission, the scheduling
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parameters are set for the process whose process ID is equal to
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.Fa pid .
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.Pp
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If
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.Fa pid
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is zero, the scheduling parameters are set for the calling process.
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.Pp
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In this implementation, the policy of when a process can affect
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the scheduling parameters of another process is specified in
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.St -p1003.1b-93
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as a write-style operation.
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.Pp
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The target process, whether it is running or not running, will resume
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execution after all other runnable processes of equal or greater
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priority have been scheduled to run.
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.Pp
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If the priority of the process specified by the
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.Fa pid
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argument is set higher than that of the lowest priority running process
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and if the specified process is ready to run, the process specified by
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the
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.Fa pid
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argument will preempt a lowest priority running process.
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Similarly, if
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the process calling
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.Fn sched_setparam
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sets its own priority lower than that of one or more other nonempty
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process lists, then the process that is the head of the highest priority
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list will also preempt the calling process.
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Thus, in either case, the
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originating process might not receive notification of the completion of
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the requested priority change until the higher priority process has
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executed.
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.Pp
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In this implementation, when the current scheduling policy for the
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process specified by
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.Fa pid
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is normal timesharing (SCHED_OTHER, aka SCHED_NORMAL when not POSIX-source)
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or the idle policy (SCHED_IDLE when not POSIX-source) then the behavior
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is as if the process had been running under SCHED_RR with a priority
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lower than any actual realtime priority.
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.Pp
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The
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.Fn sched_getparam
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system call will return the scheduling parameters of a process specified
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by
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.Fa pid
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in the
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.Fa sched_param
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structure pointed to by
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.Fa param .
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.Pp
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If a process specified by
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.Fa pid
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exists and if the calling process has permission,
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the scheduling parameters for the process whose process ID is equal to
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.Fa pid
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are returned.
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.Pp
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In this implementation, the policy of when a process can obtain the
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scheduling parameters of another process are detailed in
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.St -p1003.1b-93
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as a read-style operation.
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.Pp
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If
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.Fa pid
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is zero, the scheduling parameters for the calling process will be
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returned.
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In this implementation, the
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.Fa sched_getparam
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system call will fail if
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.Fa pid
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is negative.
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.Sh RETURN VALUES
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.Rv -std
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.Sh ERRORS
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On failure
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.Va errno
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will be set to the corresponding value:
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.Bl -tag -width Er
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.It Bq Er ENOSYS
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The system is not configured to support this functionality.
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.It Bq Er EPERM
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The requesting process doesn not have permission as detailed in
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.St -p1003.1b-93 .
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.It Bq Er ESRCH
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No process can be found corresponding to that specified by
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.Fa pid .
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.It Bq Er EINVAL
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For
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.Fn sched_setparam :
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one or more of the requested scheduling parameters
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is outside the range defined for the scheduling policy of the specified
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.Fa pid .
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.El
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.Sh SEE ALSO
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.Xr sched_get_priority_max 2 ,
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.Xr sched_get_priority_min 2 ,
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.Xr sched_getscheduler 2 ,
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.Xr sched_rr_get_interval 2 ,
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.Xr sched_setscheduler 2 ,
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.Xr sched_yield 2
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.Sh STANDARDS
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The
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.Fn sched_setparam
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and
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.Fn sched_getparam
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system calls conform to
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.St -p1003.1b-93 .
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