Multithreaded Programming Guide

Get Scheduling Parameters


pthread_attr_getschedparam(3THR) returns the scheduling parameters defined by pthread_attr_setschedparam().


int	pthread_attr_getschedparam(pthread_attr_t *tattr,
    const struct sched_param *param);
#include <pthread.h>

pthread_attr_t attr;
struct sched_param param;
int ret;

/* get the existing scheduling param */
ret = pthread_attr_getschedparam (&tattr, &param);

Return Values

pthread_attr_setschedparam() returns zero after completing successfully. Any other returned value indicates that an error occurred. If the following condition occurs, the function fails and returns the corresponding value.


The value of param is NULL or tattr is invalid.

Creating a Thread With a Specified Priority

You can set the priority attribute before creating the thread. The child thread is created with the new priority that is specified in the sched_param structure (this structure also contains other scheduling information).

It is always a good idea to get the existing parameters, change the priority, xxx the thread, and then reset the priority.

Example 3-2 shows an example of this.

Example 3-2 Creating a Prioritized Thread

#include <pthread.h>
#include <sched.h>

pthread_attr_t tattr;
pthread_t tid;
int ret;
int newprio = 20;
sched_param param;

/* initialized with default attributes */
ret = pthread_attr_init (&tattr);

/* safe to get existing scheduling param */
ret = pthread_attr_getschedparam (&tattr, &param);

/* set the priority; others are unchanged */
param.sched_priority = newprio;

/* setting the new scheduling param */
ret = pthread_attr_setschedparam (&tattr, &param);

/* with new priority specified */
ret = pthread_create (&tid, &tattr, func, arg);