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/*

 *  Thread Handler

 *

 *

 *  COPYRIGHT (c) 1989-1999.

 *  On-Line Applications Research Corporation (OAR).

 *

 *  The license and distribution terms for this file may be

 *  found in found in the file LICENSE in this distribution or at

 *  http://www.OARcorp.com/rtems/license.html.

 *

 *  $Id: threadchangepriority.c,v 1.2 2001-09-27 11:59:34 chris Exp $

 */

#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,

  boolean           prepend_it

)

{

  ISR_Level level;

  /* boolean   do_prepend = FALSE; */

  /*

   *  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.

   */

  /*

   *  Techically, the prepend should conditional on the thread lowering

   *  its priority but that does allow cxd2004 of the acvc 2.0.1 to

   *  pass with rtems 4.0.0.  This should change when gnat redoes its

   *  priority scheme.

   */

/*

  if ( prepend_it &&

       _Thread_Is_executing( the_thread ) &&

       new_priority >= the_thread->current_priority )

    prepend_it = TRUE;

*/

  _Thread_Set_transient( the_thread );

  if ( the_thread->current_priority != new_priority )

    _Thread_Set_priority( the_thread, new_priority );

  _ISR_Disable( level );

  the_thread->current_state =

    _States_Clear( STATES_TRANSIENT, the_thread->current_state );

  if ( ! _States_Is_ready( the_thread->current_state ) ) {

    /*

     *  XXX If a task is to be reordered while blocked on a priority

     *  XXX priority ordered thread queue, then this is where that

     *  XXX should occur.

     */

    _ISR_Enable( level );

    return;

  }

  _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 );

  _Thread_Calculate_heir();

  if ( !_Thread_Is_executing_also_the_heir() &&

       _Thread_Executing->is_preemptible )

    _Context_Switch_necessary = TRUE;

  _ISR_Enable( level );

}