pthread_attr_setschedpolicy(3THR)

Use pthread_attr_setschedpolicy(3THR) to set the scheduling policy. The POSIX standard specifies scheduling policy attributes of SCHED_FIFO (first-in-first-out), SCHED_RR (round-robin), or SCHED_OTHER (an implementation-defined method).

• SCHED_FIFO

  First-In-First-Out; 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, will proceed until they yield or block. SCHED_FIFO for threads that have a contention scope of process (PTHREAD_SCOPE_PROCESS) or whose calling process does not have an effective user id of 0 is based on the TS scheduling class.

• 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 they do not yield or block, will execute for a time period determined by the system. SCHED_RR for threads that have a contention scope of process (PTHREAD_SCOPE_PROCESS) or whose calling process does not have an effective user id of 0 is based on the TS scheduling class.

SCHED_FIFO and SCHED_RR are optional in POSIX, and are supported for real time bound threads only.

For a discussion of scheduling, see the section Scheduling.

Prototype:

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);

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

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

ENOTSUP

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