NAME

pthread_attr_setprio - Changes the scheduling priority attribute of thread creation

SYNOPSIS

#include <pthread.h> int pthread_attr_setprio( pthread_attr_t *attr, int priority);

PARAMETERS

attrThread attributes object modified. 

priorityNew value for the priority attribute. The priority attribute depends on scheduling policy. Valid values fall within one of the following ranges:

•PRI_OTHER_MIN <= priority <= PRI_OTHER_MAX (use with the SCHED_OTHER policy)

•PRI_FIFO_MIN <= priority <= PRI_FIFO_MAX (use with the SCHED_FIFO policy)

•PRI_RR_MIN <= priority <= PRI_RR_MAX (use with the SCHED_RR policy)

•PRI_FG_MIN_NP <= priority <= PRI_FG_MAX_NP (use with the SCHED_FG_NP policy)

•PRI_BG_MIN_NP <= priority <= PRI_BG_MAX_NP (use with the SCHED_BG_NP policy)

The default priority is the midpoint between PRI_OTHER_MIN and PRI_OTHER_MAX. To specify a minimum or maximum priority, use the appropriate symbol; for example, PRI_FIFO_MIN or PRI_FIFO_MAX. To specify a value between the minimum and maximum, use an appropriate arithmetic expression.  For example, to specify a priority midway between the minimum and maximum for the Round Robin scheduling policy, specify the following concept using your programming language’s syntax:

pri_rr_mid = (PRI_RR_MIN + PRI_RR_MAX + 1)/2

If your expression results in a value outside the range of minimum to maximum, an error results when you attempt to use it. 

DESCRIPTION

The pthread_attr_setprio() routine sets the execution priority of threads that are created using the attributes object specified by the attr parameter. By default, a created thread inherits the priority of the thread calling pthread_create(). To specify a priority using this routine, scheduling inheritance must be disabled at the time the thread is created. Before calling this routine and pthread_create(), call pthread_attr_setinheritsched() and specify the value PTHREAD_DEFAULT_SCHED for the inherit parameter. An application specifies priority only to express the urgency of executing the thread relative to other threads. Priority is not used to control mutual exclusion when accessing shared data.

RETURN VALUES

If the function fails, errno may be set to one of the following values:

RELATED INFORMATION

Functions:  pthread_attr_create(3), pthread_attr_getprio(3), pthread_attr_setinheritsched(3), pthread_create(3). 

Hewlett-Packard Company  —  OSF DCE 1.1/HP DCE 1.5