static Thread_Control *_Scheduler_priority_SMP_Get_highest_ready(
Scheduler_SMP_Control *self
)
{
Thread_Control *highest_ready = NULL;
if ( !_Priority_bit_map_Is_empty() ) {
highest_ready = _Scheduler_priority_Ready_queue_first( &self->ready[ 0 ] );
}
return highest_ready;
}
/*
* This method is invoked at the end of certain scheduling operations
* to ensure that the highest priority ready thread cannot be scheduled
* to execute. When we schedule with affinity, there is the possibility
* that we need to migrate a thread to another core to ensure that the
* highest priority ready threads are in fact scheduled.
*/
static void _Scheduler_priority_affinity_SMP_Check_for_migrations(
Scheduler_Context *context
)
{
Scheduler_priority_SMP_Context *self;
Scheduler_Node *lowest_scheduled;
Scheduler_Node *highest_ready;
self = _Scheduler_priority_SMP_Get_self( context );
while (1) {
if ( _Priority_bit_map_Is_empty( &self->Bit_map ) ) {
/* Nothing to do */
break;
}
highest_ready =
_Scheduler_priority_affinity_SMP_Get_highest_ready( context, NULL );
lowest_scheduled =
_Scheduler_priority_affinity_SMP_Get_lowest_scheduled(
context,
highest_ready,
_Scheduler_SMP_Insert_priority_lifo_order
);
/*
* If we can't find a thread to displace from the scheduled set,
* then we have placed all the highest priority threads possible
* in the scheduled set.
*
* We found the absolute highest priority thread without
* considering affinity. But now we have to consider that thread's
* affinity as we look to place it.
*/
if ( lowest_scheduled == NULL )
break;
/*
* FIXME: Do not consider threads using the scheduler helping protocol
* since this could produce more than one thread in need for help in one
* operation which is currently not possible.
*/
if ( lowest_scheduled->help_state != SCHEDULER_HELP_YOURSELF )
break;
/*
* But if we found a thread which is lower priority than one
* in the ready set, then we need to swap them out.
*/
_Scheduler_SMP_Node_change_state(
_Scheduler_SMP_Node_downcast( lowest_scheduled ),
SCHEDULER_SMP_NODE_READY
);
_Scheduler_Thread_change_state(
_Scheduler_Node_get_user( lowest_scheduled ),
THREAD_SCHEDULER_READY
);
_Scheduler_SMP_Allocate_processor(
context,
highest_ready,
lowest_scheduled,
_Scheduler_SMP_Allocate_processor_exact
);
_Scheduler_priority_SMP_Move_from_ready_to_scheduled(
context,
highest_ready
);
_Scheduler_priority_SMP_Move_from_scheduled_to_ready(
context,
lowest_scheduled
);
}
}
