sched_get_priority_max¶

Synopsis¶

#include <sched.h>

int sched_get_priority_max(int policy);

int sched_get_priority_min(int policy);

Status¶

Implemented

Conformance¶

IEEE Std 1003.1-2017

Description¶

The sched_get_priority_max() and sched_get_priority_min() functions shall return the appropriate maximum or minimum, respectively, for the scheduling policy specified by policy.

The value of policy shall be SCHED_RR, the only scheduling policy supported by Phoenix-RTOS. The returned values are POSIX priorities, as described in Scheduling priorities.

Return value¶

If successful, the sched_get_priority_max() and sched_get_priority_min() functions shall return the appropriate maximum or minimum values, respectively. If unsuccessful, they shall return a value of -1 and set errno to indicate the error.

Errors¶

The sched_get_priority_max() and sched_get_priority_min() functions shall fail if:

EINVAL - The value of the policy parameter does not represent a defined scheduling policy.
ENOTSUP - The value of the policy parameter is SCHED_FIFO or SCHED_OTHER.

POSIX deviations¶

IEEE Std 1003.1-2017 requires the functions to return the priority range of every scheduling policy defined in <sched.h>. Phoenix-RTOS supports only the SCHED_RR policy, so for SCHED_FIFO and SCHED_OTHER the functions return -1 and set errno to ENOTSUP, an error that the standard does not define for them. 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.