~drizzle-trunk/drizzle/development

/* Copyright (C) 2000 MySQL AB

   This program is free software; you can redistribute it and/or modify

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; version 2 of the License.

   This program is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License

   along with this program; if not, write to the Free Software

   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */

/* Synchronization - readers / writer thread locks */

#include "mysys_priv.h"

#if defined(THREAD) && !defined(HAVE_PTHREAD_RWLOCK_RDLOCK) && !defined(HAVE_RWLOCK_INIT)

#include <errno.h>

/*

  Source base from Sun Microsystems SPILT, simplified for MySQL use

  -- Joshua Chamas

  Some cleanup and additional code by Monty

*/

/*

*  Multithreaded Demo Source

*

*  Copyright (C) 1995 by Sun Microsystems, Inc.

*  All rights reserved.

*

*  This file is a product of SunSoft, Inc. and is provided for

*  unrestricted use provided that this legend is included on all

*  media and as a part of the software program in whole or part.

*  Users may copy, modify or distribute this file at will.

*

*  THIS FILE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING

*  THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR

*  PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.

*

*  This file is provided with no support and without any obligation on the

*  part of SunSoft, Inc. to assist in its use, correction, modification or

*  enhancement.

*

*  SUNSOFT AND SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT

*  TO THE INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS

*  FILE OR ANY PART THEREOF.

*

*  IN NO EVENT WILL SUNSOFT OR SUN MICROSYSTEMS, INC. BE LIABLE FOR ANY

*  LOST REVENUE OR PROFITS OR OTHER SPECIAL, INDIRECT AND CONSEQUENTIAL

*  DAMAGES, EVEN IF THEY HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH

*  DAMAGES.

*

*  SunSoft, Inc.

*  2550 Garcia Avenue

*  Mountain View, California  94043

*/

int my_rwlock_init(rw_lock_t *rwp, void *arg __attribute__((unused)))

{

  pthread_condattr_t	cond_attr;

  pthread_mutex_init( &rwp->lock, MY_MUTEX_INIT_FAST);

  pthread_condattr_init( &cond_attr );

  pthread_cond_init( &rwp->readers, &cond_attr );

  pthread_cond_init( &rwp->writers, &cond_attr );

  pthread_condattr_destroy(&cond_attr);

  rwp->state	= 0;

  rwp->waiters	= 0;

  return(0);

}

int my_rwlock_destroy(rw_lock_t *rwp)

{

  pthread_mutex_destroy( &rwp->lock );

  pthread_cond_destroy( &rwp->readers );

  pthread_cond_destroy( &rwp->writers );

  return(0);

}

int my_rw_rdlock(rw_lock_t *rwp)

{

  pthread_mutex_lock(&rwp->lock);

  /* active or queued writers */

  while (( rwp->state < 0 ) || rwp->waiters)

    pthread_cond_wait( &rwp->readers, &rwp->lock);

  rwp->state++;

  pthread_mutex_unlock(&rwp->lock);

  return(0);

}

int my_rw_tryrdlock(rw_lock_t *rwp)

{

  int res;

  pthread_mutex_lock(&rwp->lock);

  if ((rwp->state < 0 ) || rwp->waiters)

    res= EBUSY;					/* Can't get lock */

  else

  {

    res=0;

    rwp->state++;

  }

  pthread_mutex_unlock(&rwp->lock);

  return(res);

}

int my_rw_wrlock(rw_lock_t *rwp)

{

  pthread_mutex_lock(&rwp->lock);

  rwp->waiters++;				/* another writer queued */

  while (rwp->state)

    pthread_cond_wait(&rwp->writers, &rwp->lock);

  rwp->state	= -1;

  rwp->waiters--;

  pthread_mutex_unlock(&rwp->lock);

  return(0);

}

int my_rw_trywrlock(rw_lock_t *rwp)

{

  int res;

  pthread_mutex_lock(&rwp->lock);

  if (rwp->state)

    res= EBUSY;					/* Can't get lock */    

  else

  {

    res=0;

    rwp->state	= -1;

  }

  pthread_mutex_unlock(&rwp->lock);

  return(res);

}

int my_rw_unlock(rw_lock_t *rwp)

{

  DBUG_PRINT("rw_unlock",

	     ("state: %d waiters: %d", rwp->state, rwp->waiters));

  pthread_mutex_lock(&rwp->lock);

  if (rwp->state == -1)		/* writer releasing */

  {

    rwp->state= 0;		/* mark as available */

    if ( rwp->waiters )		/* writers queued */

      pthread_cond_signal( &rwp->writers );

    else

      pthread_cond_broadcast( &rwp->readers );

  }

  else

  {

    if ( --rwp->state == 0 )	/* no more readers */

      pthread_cond_signal( &rwp->writers );

  }

  pthread_mutex_unlock( &rwp->lock );

  return(0);

}

#endif