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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: threadrotatequeue.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_Rotate_Ready_Queue

 *

 *  This kernel routine will rotate the ready queue.

 *  remove the running THREAD from the ready chain

 *  and place it immediatly at the rear of this chain.  Reset timeslice

 *  and yield the processor functions both use this routine, therefore if

 *  reset is TRUE and this is the only thread on the chain then the

 *  timeslice counter is reset.  The heir THREAD will be updated if the

 *  running is also the currently the heir.

 *

 *  Input parameters:

 *      Priority of the queue we wish to modify.

 *

 *  Output parameters:  NONE

 *

 *  INTERRUPT LATENCY:

 *    ready chain

 *    select heir

 */

void _Thread_Rotate_Ready_Queue(

  Priority_Control  priority

)

{

  ISR_Level       level;

  Thread_Control *executing;

  Chain_Control  *ready;

  Chain_Node     *node;

  ready     = &_Thread_Ready_chain[ priority ];

  executing = _Thread_Executing;

  if ( ready == executing->ready ) {

    _Thread_Yield_processor();

    return;

  }

  _ISR_Disable( level );

  if ( !_Chain_Is_empty( ready ) ) {

    if (!_Chain_Has_only_one_node( ready ) ) {

      node = _Chain_Get_first_unprotected( ready );

      _Chain_Append_unprotected( ready, node );

    }

  }

  _ISR_Flash( level );

  if ( _Thread_Heir->ready == ready )

    _Thread_Heir = (Thread_Control *) ready->first;

  if ( executing != _Thread_Heir )

    _Context_Switch_necessary = TRUE;

  _ISR_Enable( level );

}