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pthread_attr_setschedparam

Section: C Library Functions (3)
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NAME

pthread_attr_setschedparam - Changes the values of the parameters associated with a scheduling policy of the specified thread attributes object.  

LIBRARY

DECthreads POSIX 1003.1c Library (libpthread.so)  

SYNOPSIS

#include <pthread.h>

int pthread_attr_setschedparam(
                 pthread_attr_t             *attr,
                 const struct sched_param   *param);  

STANDARDS

Interfaces documented on this reference page conform to industry standards as follows:

IEEE Std 1003.1c-1995, POSIX System Application Program Interface  

PARAMETERS

Thread attributes object for the scheduling policy whose parameters are to be set. A structure containing new values for scheduling parameters associated with the scheduling policy attribute of the specified thread attributes object. Note that DECthreads provides only the sched_priority scheduling parameter. It allows specifying the scheduling priority. See the Description section for information about this scheduling parameter.  

DESCRIPTION

This routine sets the scheduling parameters associated with the scheduling policy attribute of the thread attributes object specified by the attr argument.

Use the sched_priority field of a sched_param structure to set a thread's execution priority. The effect of the scheduling priority you assign depends on the scheduling policy specified for the attributes object specified by the attr argument.

By default, a created thread inherits the priority of the thread calling pthread_create(3). To specify a priority using this routine, scheduling inheritance must be disabled at the time the thread is created. Before calling pthread_create(3), call pthread_attr_setinheritsched(3) and specify the value PTHREAD_EXPLICIT_SCHED for the inherit argument.

An application specifies priority only to express the urgency of executing the thread relative to other threads. DO NOT USE PRIORITY TO CONTROL MUTUAL EXCLUSION WHEN ACCESSING SHARED DATA. With a sufficient number of processors present, all ready threads, regardless of priority, execute simultaneously.

Valid values of the sched_priority scheduling parameter depend on the chosen scheduling policy. Use the POSIX routines sched_get_priority_min(3) or sched_get_priority_max(3) to determine the low and high limits of each policy.

Additionally, DECthreads provides nonportable priority range constants, as follows: PRI_FIFO_MIN to PRI_FIFO_MAX PRI_RR_MIN to PRI_RR_MAX PRI_OTHER_MIN to PRI_OTHER_MAX PRI_FG_MIN_NP to PRI_FG_MAX_NP PRI_BG_MIN_NP to PRI_BG_MAX_NP

The default priority varies by DECthreads platform. On Tru64 UNIX, the default is 19 (that is, the POSIX priority of a normal timeshare process). On other platforms, the default priority is the midpoint between PRI_FG_MIN_NP and PRI_FG_MAX_NP.

 

RETURN VALUES

If an error condition occurs, this routine returns an integer value indicating the type of error. Possible return values are as follows: Successful completion. The value specified by param is invalid. An attempt was made to set the attribute to an unsupported value.  

ERRORS

None  

RELATED INFORMATION

Functions: pthread_attr_init(3), pthread_attr_getschedparam(3), pthread_attr_setinheritsched(3), pthread_attr_setschedpolicy(3), pthread_create(3), sched_yield(3)

Manuals: Guide to DECthreads and Programmer's Guide

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Index

NAME
LIBRARY
SYNOPSIS
STANDARDS
PARAMETERS
DESCRIPTION
RETURN VALUES
ERRORS
RELATED INFORMATION

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Time: 02:40:58 GMT, October 02, 2010