/* 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; either version 2 of the License, or (at your option) any later version. 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" #include <my_pthread.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