A.8 HP-UX-Specific Considerations

On HP-UX, appropriate privileges are required to change the scheduling parameters of a task. The calling process must have appropriate privileges or be a member of a group having PRIV_RTSCHED access to successfully change the scheduling parameters.

By default, GNAT uses the SCHED_HPUX policy. To have access to the priority range 0-31 either the FIFO_Within_Priorities or the Round_Robin_Within_Priorities scheduling policies need to be set.

To specify the FIFO_Within_Priorities scheduling policy you can use one of the following:

• pragma Time_Slice (0.0)
• the corresponding binder option -T0
• pragma Task_Dispatching_Policy (FIFO_Within_Priorities)

To specify the Round_Robin_Within_Priorities, scheduling policy you should use pragma Time_Slice with a value greater than 0.0, or use the corresponding -T binder option, or set the pragma Task_Dispatching_Policy (Round_Robin_Within_Priorities).