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/*
 *  CORE Semaphore Handler
 *
 *  DESCRIPTION:
 *
 *  This package is the implementation of the CORE Semaphore Handler.
 *  This core object utilizes standard Dijkstra counting semaphores to provide
 *  synchronization and mutual exclusion capabilities.
 *
 *  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.OARcorp.com/rtems/license.html.
 *
 *  $Id: coresemseize.c,v 1.2 2001-09-27 11:59:34 chris Exp $
 */
 
#include <rtems/system.h>
#include <rtems/score/isr.h>
#include <rtems/score/coresem.h>
#include <rtems/score/states.h>
#include <rtems/score/thread.h>
#include <rtems/score/threadq.h>
#if defined(RTEMS_MULTIPROCESSING)
#include <rtems/score/mpci.h>
#endif
 
/*PAGE
 *
 *  _CORE_semaphore_Seize
 *
 *  This routine attempts to allocate a core semaphore to the calling thread.
 *
 *  Input parameters:
 *    the_semaphore - pointer to semaphore control block
 *    id            - id of object to wait on
 *    wait          - TRUE if wait is allowed, FALSE otherwise
 *    timeout       - number of ticks to wait (0 means forever)
 *
 *  Output parameters:  NONE
 *
 *  INTERRUPT LATENCY:
 *    available
 *    wait
 */
 
void _CORE_semaphore_Seize(
  CORE_semaphore_Control  *the_semaphore,
  Objects_Id               id,
  boolean                  wait,
  Watchdog_Interval        timeout
)
{
  Thread_Control *executing;
  ISR_Level       level;
 
  executing = _Thread_Executing;
  executing->Wait.return_code = CORE_SEMAPHORE_STATUS_SUCCESSFUL;
  _ISR_Disable( level );
  if ( the_semaphore->count != 0 ) {
    the_semaphore->count -= 1;
    _ISR_Enable( level );
    return;
  }
 
  if ( !wait ) {
    _ISR_Enable( level );
    executing->Wait.return_code = CORE_SEMAPHORE_STATUS_UNSATISFIED_NOWAIT;
    return;
  }
 
  _Thread_queue_Enter_critical_section( &the_semaphore->Wait_queue );
  executing->Wait.queue          = &the_semaphore->Wait_queue;
  executing->Wait.id             = id;
  _ISR_Enable( level );
 
  _Thread_queue_Enqueue( &the_semaphore->Wait_queue, timeout );
}