The pthread_setschedparam() and pthread_getschedparam() functions set and get the scheduling parameters of individual threads. The scheduling policy for a thread can be:
SCHED_FIFO
First in, first out.
SCHED_RR
Round-robin.
SCHED_OTHER
The system default.
The thread priority (accessed via param->sched_priority) must be at least PTHREAD_MIN_PRIORITY and no more than PTHREAD_MAX_PRIORITY.
RETURN VALUES
If successful, these functions return 0. Otherwise, an error number is returned to indicate the error.