/*
 *  SuperCore RWLock Handler -- Release a RWLock
 *
 *  COPYRIGHT (c) 1989-2006.
 *  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/corerwlock.h>
#include <rtems/score/states.h>
#include <rtems/score/thread.h>
#include <rtems/score/watchdog.h>

/*PAGE
 *
 *  _CORE_RWLock_Release
 *
 *  This function releases the rwlock.
 *
 *  Input parameters:
 *    the_rwlock    - the rwlock control block to initialize
 *
 *  Output parameters:  NONE
 */

CORE_RWLock_Status _CORE_RWLock_Release(
  CORE_RWLock_Control  *the_rwlock
)
{
  ISR_Level       level;
  Thread_Control *executing = _Thread_Executing;

  /*
   *  If unlocked, then OK to read.
   *  Otherwise, we have to block.
   *  If locked for reading and no waiters, then OK to read.
   *  If any thread is waiting, then we wait.
   */

  _ISR_Disable( level );
    switch ( the_rwlock->current_state ) {
      case CORE_RWLOCK_UNLOCKED:
	_ISR_Enable( level );
	executing->Wait.return_code = CORE_RWLOCK_UNAVAILABLE;
        return CORE_RWLOCK_SUCCESSFUL;

      case CORE_RWLOCK_LOCKED_FOR_READING:
	the_rwlock->number_of_readers -= 1;
	if ( the_rwlock->number_of_readers != 0 ) {
          /* must be unlocked again */
	  _ISR_Enable( level );
          return CORE_RWLOCK_SUCCESSFUL;
        }
	executing->Wait.return_code = CORE_RWLOCK_SUCCESSFUL;
        break;
      case CORE_RWLOCK_LOCKED_FOR_WRITING:
        break;
    }

    /*
     * Implicitly transition to "unlocked" and find another thread interested
     * in obtaining this rwlock.
     */

    /* XXX need to put read/write lock request indicator in Wait info */

    /* XXX find one writer or multiple readers to take off */
  _ISR_Enable( level );
  return CORE_RWLOCK_SUCCESSFUL;
}