pthread_attr_setschedpolicy

Synopsis

#include <pthread.h>

int pthread_attr_getschedpolicy(const pthread_attr_t *restrict attr,
                                int *restrict policy);

int pthread_attr_setschedpolicy(pthread_attr_t *attr, int policy);

Status

Implemented

Conformance

IEEE Std 1003.1-2017

Description

The pthread_attr_getschedpolicy() and pthread_attr_setschedpolicy() functions, respectively, shall get and set the schedpolicy attribute in the attr argument.

The supported value of policy is SCHED_RR, which is defined in the <sched.h> header. It is also the default value of the attribute. When threads executing with the scheduling policy SCHED_RR are waiting on a mutex, they shall acquire the mutex in priority order when the mutex is unlocked.

The behavior is undefined if the value specified by the attr argument to pthread_attr_getschedpolicy() or pthread_attr_setschedpolicy() does not refer to an initialized thread attributes object.

Return value

If successful, the pthread_attr_getschedpolicy() and pthread_attr_setschedpolicy() functions shall return zero; otherwise, an error number shall be returned to indicate the error.

Errors

The pthread_attr_setschedpolicy() function shall fail if:

• ENOTSUP - An attempt was made to set the attribute to an unsupported value (SCHED_FIFO or SCHED_OTHER).

The pthread_attr_setschedpolicy() function may fail if:

• EINVAL - The value of policy is not valid.

These functions shall not return an error code of EINTR.

POSIX deviations

IEEE Std 1003.1-2017 requires the supported values of policy to include SCHED_FIFO, SCHED_RR and SCHED_OTHER. Phoenix-RTOS supports only SCHED_RR, and pthread_attr_setschedpolicy() returns ENOTSUP for SCHED_FIFO and SCHED_OTHER. The Phoenix-RTOS kernel schedules all threads with a single priority-based round-robin policy, which keeps the scheduler small and its behaviour predictable on resource-constrained real-time targets. See Scheduling priorities for the mapping of POSIX priorities.