diff options
Diffstat (limited to 'externals/mysql/mysys/thr_rwlock.c')
| -rw-r--r-- | externals/mysql/mysys/thr_rwlock.c | 171 |
1 files changed, 171 insertions, 0 deletions
diff --git a/externals/mysql/mysys/thr_rwlock.c b/externals/mysql/mysys/thr_rwlock.c new file mode 100644 index 00000000000..280a0ec19e7 --- /dev/null +++ b/externals/mysql/mysys/thr_rwlock.c @@ -0,0 +1,171 @@ +/* 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 |