KPRIORITY
KeSetPriorityThread(
IN PKTHREAD Thread,
IN KPRIORITY Priority
);
KeSetPriorityThread sets the runtime priority of a driver-created thread.
KeSetPriorityThread returns the old priority of the thread.
If a call to KeSetPriorityThread resets the thread’s priority to a lower value, execution of the thread can be rescheduled even if it is currently running or is about to be dispatched for execution.
Callers of KeSetPriorityThread must be running at IRQL PASSIVE_LEVEL.