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/*
* Thread Handler / Change Priority
*
* COPYRIGHT (c) 1989-2011.
* 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/apiext.h>
#include <rtems/score/context.h>
#include <rtems/score/interr.h>
#include <rtems/score/isr.h>
#include <rtems/score/object.h>
#include <rtems/score/priority.h>
#include <rtems/score/states.h>
#include <rtems/score/sysstate.h>
#include <rtems/score/thread.h>
#include <rtems/score/threadq.h>
#include <rtems/score/userext.h>
#include <rtems/score/wkspace.h>
/*PAGE
*
* _Thread_Change_priority
*
* This kernel routine changes the priority of the thread. The
* thread chain is adjusted if necessary.
*
* Input parameters:
* the_thread - pointer to thread control block
* new_priority - ultimate priority
* prepend_it - true if the thread should be prepended to the chain
*
* Output parameters: NONE
*
* INTERRUPT LATENCY:
* ready chain
* select heir
*/
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.
*/
the_thread->current_state = _States_Clear( STATES_TRANSIENT, state );
_Priority_Add_to_bit_map( &the_thread->Priority_map );
if ( prepend_it )
_Chain_Prepend_unprotected( the_thread->ready, &the_thread->Object.Node );
else
_Chain_Append_unprotected( the_thread->ready, &the_thread->Object.Node );
}
_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.
*/
_Thread_Calculate_heir();
if ( !_Thread_Is_executing_also_the_heir() &&
_Thread_Executing->is_preemptible )
_Context_Switch_necessary = true;
_ISR_Enable( level );
}
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