$FreeBSD: releng/11.0/lib/libc/sys/sched_setparam.2 131594 2004-07-04 20:55:50Z ru $ Copyright (c) 1998 HD Associates, Inc. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notic...
NAMEsched_setparam sched_getparam - set/get scheduling parameters
SYNOPSISIn sched.h Ft int Fn sched_setparam pid_t pid const struct sched_param *param Ft int Fn sched_getparam pid_t pid struct sched_param *param
DESCRIPTIONThe Fn sched_setparam system call sets the scheduling parameters of the process specified by Fa pid to the values specified by the Fa sched_param structure pointed to by Fa param . The value of the Fa sched_priority member in the Fa param structure must be any integer within the inclusive priority range for the current scheduling policy of the process specified by Fa pid . Higher numerical values for the priority represent higher priorities.
In this implementation, if the value of Fa pid is negative the system call will fail.
If a process specified by Fa pid exists and if the calling process has permission, the scheduling parameters are set for the process whose process ID is equal to Fa pid .
If Fa pid is zero, the scheduling parameters are set for the calling process.
In this implementation, the policy of when a process can affect the scheduling parameters of another process is specified in St -p1003.1b-93 as a write-style operation.
The target process, whether it is running or not running, will resume execution after all other runnable processes of equal or greater priority have been scheduled to run.
If the priority of the process specified by the Fa pid argument is set higher than that of the lowest priority running process and if the specified process is ready to run, the process specified by the Fa pid argument will preempt a lowest priority running process. Similarly, if the process calling Fn sched_setparam sets its own priority lower than that of one or more other nonempty process lists, then the process that is the head of the highest priority list will also preempt the calling process. Thus, in either case, the originating process might not receive notification of the completion of the requested priority change until the higher priority process has executed.
In this implementation, when the current scheduling policy for the process specified by Fa pid is normal timesharing (SCHED_OTHER, aka SCHED_NORMAL when not POSIX-source) or the idle policy (SCHED_IDLE when not POSIX-source) then the behavior is as if the process had been running under SCHED_RR with a priority lower than any actual realtime priority.
The Fn sched_getparam system call will return the scheduling parameters of a process specified by Fa pid in the Fa sched_param structure pointed to by Fa param .
If a process specified by Fa pid exists and if the calling process has permission, the scheduling parameters for the process whose process ID is equal to Fa pid are returned.
In this implementation, the policy of when a process can obtain the scheduling parameters of another process are detailed in St -p1003.1b-93 as a read-style operation.
If Fa pid is zero, the scheduling parameters for the calling process will be returned. In this implementation, the Fa sched_getparam system call will fail if Fa pid is negative.
RETURN VALUESRv -std
ERRORSOn failure errno will be set to the corresponding value:
- Bq Er ENOSYS
- The system is not configured to support this functionality.
- Bq Er EPERM
- The requesting process doesn not have permission as detailed in St -p1003.1b-93 .
- Bq Er ESRCH
- No process can be found corresponding to that specified by Fa pid .
- Bq Er EINVAL
- For Fn sched_setparam : one or more of the requested scheduling parameters is outside the range defined for the scheduling policy of the specified Fa pid .