Import changeset

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