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/*
* Thread Handler
*
*
* COPYRIGHT (c) 1989-2006.
* On-Line Applications Research Corporation (OAR).
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.rtems.com/license/LICENSE.
*
* $Id$
*/
#if HAVE_CONFIG_H
#include "config.h"
#endif
#include <rtems/system.h>
#include <rtems/score/isr.h>
#include <rtems/score/scheduler.h>
#include <rtems/score/schedulerpriority.h>
#include <rtems/score/thread.h>
#include <rtems/score/threadq.h>
void _Thread_Change_priority(
Thread_Control *the_thread,
Priority_Control new_priority,
bool prepend_it
)
{
ISR_Level level;
States_Control state, original_state;
/*
* If this is a case where prepending the task to its priority is
* potentially desired, then we need to consider whether to do it.
* This usually occurs when a task lowers its priority implcitly as
* the result of losing inherited priority. Normal explicit priority
* change calls (e.g. rtems_task_set_priority) should always do an
* append not a prepend.
*/
/*
if ( prepend_it &&
_Thread_Is_executing( the_thread ) &&
new_priority >= the_thread->current_priority )
prepend_it = true;
*/
/*
* Save original state
*/
original_state = the_thread->current_state;
/*
* Set a transient state for the thread so it is pulled off the Ready chains.
* This will prevent it from being scheduled no matter what happens in an
* ISR.
*/
_Thread_Set_transient( the_thread );
/*
* Do not bother recomputing all the priority related information if
* we are not REALLY changing priority.
*/
if ( the_thread->current_priority != new_priority )
_Thread_Set_priority( the_thread, new_priority );
_ISR_Disable( level );
/*
* If the thread has more than STATES_TRANSIENT set, then it is blocked,
* If it is blocked on a thread queue, then we need to requeue it.
*/
state = the_thread->current_state;
if ( state != STATES_TRANSIENT ) {
/* Only clear the transient state if it wasn't set already */
if ( ! _States_Is_transient( original_state ) )
the_thread->current_state = _States_Clear( STATES_TRANSIENT, state );
_ISR_Enable( level );
if ( _States_Is_waiting_on_thread_queue( state ) ) {
_Thread_queue_Requeue( the_thread->Wait.queue, the_thread );
}
return;
}
/* Only clear the transient state if it wasn't set already */
if ( ! _States_Is_transient( original_state ) ) {
/*
* Interrupts are STILL disabled.
* We now know the thread will be in the READY state when we remove
* the TRANSIENT state. So we have to place it on the appropriate
* Ready Queue with interrupts off.
*
* FIXME: hard-coded for priority scheduling. Might be ok since this
* function is specific to priority scheduling?
*/
the_thread->current_state = _States_Clear( STATES_TRANSIENT, state );
if ( prepend_it )
_Scheduler_priority_Ready_queue_enqueue_first( the_thread );
else
_Scheduler_priority_Ready_queue_enqueue( the_thread );
}
_ISR_Flash( level );
/*
* We altered the set of thread priorities. So let's figure out
* who is the heir and if we need to switch to them.
*/
_Scheduler_Schedule();
if ( !_Thread_Is_executing_also_the_heir() &&
_Thread_Executing->is_preemptible )
_Thread_Dispatch_necessary = true;
_ISR_Enable( level );
}
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