Setting the Scheduling Policy

Use pthread_attr_setschedpolicy(3C) to set the scheduling policy. The POSIX standard specifies the scheduling policy values of SCHED_FIFO (first-in-first-out), SCHED_RR (round-robin), or SCHED_OTHER (an implementation-defined method). In the Solaris OS, SCHED_OTHER threads run in the traditional time-sharing (TS) scheduling class.

pthread_attr_setschedpolicy(3C) Syntax

int pthread_attr_setschedpolicy(pthread_attr_t *tattr, int policy);

#include <pthread.h> 
pthread_attr_t tattr; 
int policy; 
int ret; 

/* set the scheduling policy to SCHED_OTHER */ 
ret = pthread_attr_setschedpolicy(&tattr, SCHED_OTHER);

• SCHED_FIFO

  A First-In-First-Out thread runs in the real-time (RT) scheduling class and require the calling process to be privileged. Such a thread, if not preempted by a higher priority thread, executes until it yields or blocks.

• SCHED_RR

  Round-Robin threads whose contention scope is system (PTHREAD_SCOPE_SYSTEM) are in real-time (RT) scheduling class if the calling process has an effective user id of 0. These threads, if not preempted by a higher priority thread, and if the threads do not yield or block, will execute for the system-determined time period. Use SCHED_RR for threads that have a contention scope of process (PTHREAD_SCOPE_PROCESS) is based on the TS scheduling class. Additionally, the calling process for these threads does not have an effective userid of 0.

  A Round-Robin thread runs in the real-time (RT) scheduling class and requires the calling process to be privileged. If a round robin thread is not preempted by a higher priority thread, and does not yield or block, it will execute for a system-determined time period. The thread is then forced to yield to another real time thread of equal priority.

SCHED_FIFO and SCHED_RR are optional in the POSIX standard, and are supported for real-time threads only.

For a discussion of scheduling, see the section Thread Scheduling.

pthread_attr_setschedpolicy Return Values

pthread_attr_setschedpolicy() returns zero after completing successfully. Any other return value indicates that an error occurred. When either of the following conditions occurs, the function fails and returns the corresponding value.

EINVAL

Description:

An attempt was made to set tattr to a value that is not valid.

ENOTSUP

Description:

An attempt was made to set the attribute to an unsupported value.