diff options
Diffstat (limited to 'mysys/thr_rwlock.c')
| -rw-r--r-- | mysys/thr_rwlock.c | 139 |
1 files changed, 139 insertions, 0 deletions
diff --git a/mysys/thr_rwlock.c b/mysys/thr_rwlock.c new file mode 100644 index 00000000000..fc2eea551da --- /dev/null +++ b/mysys/thr_rwlock.c @@ -0,0 +1,139 @@ +/* Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult AB + + This library is free software; you can redistribute it and/or + modify it under the terms of the GNU Library General Public + License as published by the Free Software Foundation; either + version 2 of the License, or (at your option) any later version. + + This library 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 + Library General Public License for more details. + + You should have received a copy of the GNU Library General Public + License along with this library; 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) + +/* + * Source base from Sun Microsystems SPILT, simplified + * for MySQL use -- Joshua Chamas + */ + +/* +* 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, NULL ); + 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_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; + + if ( ( --rwp->waiters == 0 ) && ( rwp->state >= 0 ) ) + pthread_cond_broadcast( &rwp->readers ); + + pthread_mutex_unlock( &rwp->lock ); + + return( 0 ); +} + +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 |