pthread_attr_setprio

Changes the scheduling priority attribute of thread creation.

Syntax

pthread_attr_setprio( attr, priority );

Argument Data Type Access

attr opaque pthread_attr_t read priority integer read

C Binding

int
pthread_attr_setprio (
pthread_attr_t *attr,
int priority);

Arguments

attr

Thread attributes object modified.

priority

New value for the priority attribute. The priority attribute is dependent upon scheduling policy. Valid values fall within one of the following ranges:

Low High

PRI_FIFO_MIN PRI_FIFO_MAX PRI_RR_MIN PRI_RR_MAX PRI_OTHER_MIN PRI_OTHER_MAX PRI_FG_MIN_NP PRI_FG_MAX_NP PRI_BG_MIN_NP PRI_BG_MAX_NP

The default priority is the midpoint between PRI_OTHER_MIN and PRI_ OTHER_MAX. (Section 2.7 describes how to specify priorities between the minimum and maximum values.)

Description

This routine sets the execution priority of threads that are created using the attributes object specified by the attr argument.

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. Call pthread_attr_setinheritsched and specify the value PTHREAD_DEFAULT_SCHED for the inherit argument before calling pthread_create.

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. With a sufficient number of processors executing, all ready threads, regardless of priority, execute simultaneously.

Return Values

If an error condition occurs, this routine returns -1 and sets errno to the corresponding error value. Possible return values are as follows:

Return Error Description

0 Successful completion. -1 [EINVAL] The value specified by priority is invalid. -1 [ERANGE] One or more arguments supplied have an invalid value.