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 Oracle 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 user id 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.

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

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