1.\" $FreeBSD: src/lib/libc/sys/sched_setparam.2,v 1.4.2.8 2001/12/14 18:34:01 ru Exp $ 2.\" $DragonFly: src/lib/libc/sys/sched_setparam.2,v 1.3 2006/04/08 07:23:35 swildner Exp $ 3.\" Copyright (c) 1998 HD Associates, Inc. 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25.\" SUCH DAMAGE. 26.\" 27.Dd March 12, 1998 28.Dt SCHED_SETPARAM 2 29.Os 30.Sh NAME 31.Nm sched_setparam , 32.Nm sched_getparam 33.Nd set/get scheduling parameters 34.Sh LIBRARY 35.Lb libc 36.Sh SYNOPSIS 37.In sched.h 38.Ft int 39.Fn sched_setparam "pid_t pid" "const struct sched_param *param" 40.Ft int 41.Fn sched_getparam "pid_t pid" "struct sched_param *param" 42.Sh DESCRIPTION 43The 44.Fn sched_setparam 45function sets the scheduling parameters of the process specified by 46.Fa pid 47to the values specified by the 48.Fa sched_param 49structure pointed to by 50.Fa param . 51The value of the 52.Fa sched_priority 53member in the 54.Fa param 55structure must be any integer within the inclusive priority range for 56the current scheduling policy of the process specified by 57.Fa pid . 58Higher numerical values for the priority represent higher priorities. 59.Pp 60In this implementation, if the value of 61.Fa pid 62is negative the function will fail. 63.Pp 64If a process specified by 65.Fa pid 66exists and if the calling process has permission, the scheduling 67parameters are set for the process whose process ID is equal to 68.Fa pid . 69.Pp 70If 71.Fa pid 72is zero, the scheduling parameters are set for the calling process. 73.Pp 74In this implementation, the policy of when a process can affect 75the scheduling parameters of another process is specified in 76.St -p1003.1b-93 77as a write-style operation. 78.Pp 79The target process, whether it is running or not running, will resume 80execution after all other runnable processes of equal or greater 81priority have been scheduled to run. 82.Pp 83If the priority of the process specified by the 84.Fa pid 85argument is set higher than that of the lowest priority running process 86and if the specified process is ready to run, the process specified by 87the 88.Fa pid 89argument will preempt a lowest priority running process. Similarly, if 90the process calling 91.Fn sched_setparam 92sets its own priority lower than that of one or more other nonempty 93process lists, then the process that is the head of the highest priority 94list will also preempt the calling process. Thus, in either case, the 95originating process might not receive notification of the completion of 96the requested priority change until the higher priority process has 97executed. 98.Pp 99In this implementation, when the current scheduling policy for the 100process specified by 101.Fa pid 102is normal timesharing (SCHED_OTHER, aka SCHED_NORMAL when not POSIX-source) 103or the idle policy (SCHED_IDLE when not POSIX-source) then the behavior 104is as if the process had been running under SCHED_RR with a priority 105lower than any actual realtime priority. 106.Pp 107The 108.Fn sched_getparam 109function will return the scheduling parameters of a process specified 110by 111.Fa pid 112in the 113.Fa sched_param 114structure pointed to by 115.Fa param . 116.Pp 117If a process specified by 118.Fa pid 119exists and if the calling process has permission, 120the scheduling parameters for the process whose process ID is equal to 121.Fa pid 122are returned. 123.Pp 124In this implementation, the policy of when a process can obtain the 125scheduling parameters of another process are detailed in 126.St -p1003.1b-93 127as a read-style operation. 128.Pp 129If 130.Fa pid 131is zero, the scheduling parameters for the calling process will be 132returned. In this implementation, the 133.Fa sched_getparam 134function will fail if 135.Fa pid 136is negative. 137.Sh RETURN VALUES 138.Rv -std 139.Sh ERRORS 140On failure 141.Va errno 142will be set to the corresponding value: 143.Bl -tag -width Er 144.It Bq Er ENOSYS 145The system is not configured to support this functionality. 146.It Bq Er EPERM 147The requesting process doesn not have permission as detailed in 148.St -p1003.1b-93 . 149.It Bq Er ESRCH 150No process can be found corresponding to that specified by 151.Fa pid . 152.It Bq Er EINVAL 153For 154.Fn sched_setparam : 155one or more of the requested scheduling parameters 156is outside the range defined for the scheduling policy of the specified 157.Fa pid . 158.El 159.Sh SEE ALSO 160.Xr sched_getscheduler 2 , 161.Xr sched_get_priority_max 2 , 162.Xr sched_get_priority_min 2 , 163.Xr sched_rr_get_interval 2 , 164.Xr sched_setscheduler 2 , 165.Xr sched_yield 2 166.Sh STANDARDS 167The 168.Fn sched_setparam 169and 170.Fn sched_getparam 171functions conform to 172.St -p1003.1b-93 . 173