summaryrefslogtreecommitdiff
path: root/mysys/thr_rwlock.c
diff options
context:
space:
mode:
Diffstat (limited to 'mysys/thr_rwlock.c')
-rw-r--r--mysys/thr_rwlock.c139
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