threadqdequeuepriority.c

RTEMS (Real-Time Executive for Multiprocessor Systems) is a free open source real-time operating sys

/*
 *  Thread Queue Handler
 *
 *
 *  COPYRIGHT (c) 1989-1999.
 *  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: threadqdequeuepriority.c,v 1.2.6.1 2003/09/04 18:52:48 joel Exp $
 */

#include <rtems/system.h>
#include <rtems/score/chain.h>
#include <rtems/score/isr.h>
#include <rtems/score/object.h>
#include <rtems/score/states.h>
#include <rtems/score/thread.h>
#include <rtems/score/threadq.h>
#include <rtems/score/tqdata.h>

/*PAGE
 *
 *  _Thread_queue_Dequeue_priority
 *
 *  This routine removes a thread from the specified PRIORITY based
 *  threadq, unblocks it, and cancels its timeout timer.
 *
 *  Input parameters:
 *    the_thread_queue - pointer to thread queue
 *
 *  Output parameters:
 *    returns - thread dequeued or NULL
 *
 *  INTERRUPT LATENCY:
 *    only case
 */

Thread_Control *_Thread_queue_Dequeue_priority(
  Thread_queue_Control *the_thread_queue
)
{
  unsigned32      index;
  ISR_Level       level;
  Thread_Control *the_thread = NULL;  /* just to remove warnings */
  Thread_Control *new_first_thread;
  Chain_Node     *new_first_node;
  Chain_Node     *new_second_node;
  Chain_Node     *last_node;
  Chain_Node     *next_node;
  Chain_Node     *previous_node;

  _ISR_Disable( level );
  for( index=0 ;
       index < TASK_QUEUE_DATA_NUMBER_OF_PRIORITY_HEADERS ;
       index++ ) {
    if ( !_Chain_Is_empty( &the_thread_queue->Queues.Priority[ index ] ) ) {
      the_thread = (Thread_Control *)
                    the_thread_queue->Queues.Priority[ index ].first;
      goto dequeue;
    }
  }

  switch ( the_thread_queue->sync_state ) {
    case THREAD_QUEUE_SYNCHRONIZED:
    case THREAD_QUEUE_SATISFIED:
      _ISR_Enable( level );
      return NULL;

    case THREAD_QUEUE_NOTHING_HAPPENED:
    case THREAD_QUEUE_TIMEOUT:
      the_thread_queue->sync_state = THREAD_QUEUE_SATISFIED;
      _ISR_Enable( level );
      return _Thread_Executing;
  }

dequeue:
  new_first_node   = the_thread->Wait.Block2n.first;
  new_first_thread = (Thread_Control *) new_first_node;
  next_node        = the_thread->Object.Node.next;
  previous_node    = the_thread->Object.Node.previous;

  if ( !_Chain_Is_empty( &the_thread->Wait.Block2n ) ) {
    last_node       = the_thread->Wait.Block2n.last;
    new_second_node = new_first_node->next;

    previous_node->next      = new_first_node;
    next_node->previous      = new_first_node;
    new_first_node->next     = next_node;
    new_first_node->previous = previous_node;

    if ( !_Chain_Has_only_one_node( &the_thread->Wait.Block2n ) ) {
                                                /* > two threads on 2-n */
      new_second_node->previous =
                _Chain_Head( &new_first_thread->Wait.Block2n );

      new_first_thread->Wait.Block2n.first = new_second_node;
      new_first_thread->Wait.Block2n.last  = last_node;

      last_node->next = _Chain_Tail( &new_first_thread->Wait.Block2n );
    }
  } else {
    previous_node->next = next_node;
    next_node->previous = previous_node;
  }

  if ( !_Watchdog_Is_active( &the_thread->Timer ) ) {
    _ISR_Enable( level );
    _Thread_Unblock( the_thread );
  } else {
    _Watchdog_Deactivate( &the_thread->Timer );
    _ISR_Enable( level );
    (void) _Watchdog_Remove( &the_thread->Timer );
    _Thread_Unblock( the_thread );
  }

#if defined(RTEMS_MULTIPROCESSING)
  if ( !_Objects_Is_local_id( the_thread->Object.id ) )
    _Thread_MP_Free_proxy( the_thread );
#endif
  return( the_thread );
}