/* $OpenLDAP$ */
+/* This work is part of OpenLDAP Software <http://www.openldap.org/>.
+ *
+ * Copyright 1998-2007 The OpenLDAP Foundation.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+/* This work was initially developed by Kurt D. Zeilenga for inclusion
+ * in OpenLDAP Software. Additional significant contributors include:
+ * Stuart Lynne
+ */
+
/*
-** This is an improved implementation of Reader/Writer locks does
-** not protect writers from starvation. That is, if a writer is
-** currently waiting on a reader, any new reader will get
-** the lock before the writer.
-**
-** Does not support cancellation nor does any status checking.
-*/
+ * This is an improved implementation of Reader/Writer locks does
+ * not protect writers from starvation. That is, if a writer is
+ * currently waiting on a reader, any new reader will get
+ * the lock before the writer.
+ *
+ * Does not support cancellation nor does any status checking.
+ */
/* Adapted from publically available examples for:
* "Programming with Posix Threads"
* by David R Butenhof, Addison-Wesley
#include <ac/errno.h>
#include <ac/string.h>
+#include <ac/time.h>
-#include "ldap_pvt_thread.h"
+#include "ldap-int.h"
+#include "ldap_pvt_thread.h" /* Get the thread interface */
+#define LDAP_THREAD_RDWR_IMPLEMENTATION
+#include "ldap_thr_debug.h" /* May rename the symbols defined below */
/*
* implementations that provide their own compatible
*/
#ifndef LDAP_THREAD_HAVE_RDWR
+struct ldap_int_thread_rdwr_s {
+ ldap_pvt_thread_mutex_t ltrw_mutex;
+ ldap_pvt_thread_cond_t ltrw_read; /* wait for read */
+ ldap_pvt_thread_cond_t ltrw_write; /* wait for write */
+ int ltrw_valid;
+#define LDAP_PVT_THREAD_RDWR_VALID 0x0bad
+ int ltrw_r_active;
+ int ltrw_w_active;
+ int ltrw_r_wait;
+ int ltrw_w_wait;
+#ifdef LDAP_RDWR_DEBUG
+ /* keep track of who has these locks */
+#define MAX_READERS 32
+ int ltrw_more_readers; /* Set if ltrw_readers[] is incomplete */
+ ldap_pvt_thread_t ltrw_readers[MAX_READERS];
+ ldap_pvt_thread_t ltrw_writer;
+#endif
+};
+
int
-ldap_pvt_thread_rdwr_init( ldap_pvt_thread_rdwr_t *rw )
+ldap_pvt_thread_rdwr_init( ldap_pvt_thread_rdwr_t *rwlock )
{
- assert( rw != NULL );
+ struct ldap_int_thread_rdwr_s *rw;
+
+ assert( rwlock != NULL );
- memset( rw, 0, sizeof(ldap_pvt_thread_rdwr_t) );
+ rw = (struct ldap_int_thread_rdwr_s *) LDAP_CALLOC( 1,
+ sizeof( struct ldap_int_thread_rdwr_s ) );
+ if ( !rw )
+ return LDAP_NO_MEMORY;
/* we should check return results */
ldap_pvt_thread_mutex_init( &rw->ltrw_mutex );
ldap_pvt_thread_cond_init( &rw->ltrw_write );
rw->ltrw_valid = LDAP_PVT_THREAD_RDWR_VALID;
+
+ *rwlock = rw;
return 0;
}
int
-ldap_pvt_thread_rdwr_destroy( ldap_pvt_thread_rdwr_t *rw )
+ldap_pvt_thread_rdwr_destroy( ldap_pvt_thread_rdwr_t *rwlock )
{
+ struct ldap_int_thread_rdwr_s *rw;
+
+ assert( rwlock != NULL );
+ rw = *rwlock;
+
assert( rw != NULL );
assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
+ assert( rw->ltrw_w_active >= 0 );
+ assert( rw->ltrw_w_wait >= 0 );
+ assert( rw->ltrw_r_active >= 0 );
+ assert( rw->ltrw_r_wait >= 0 );
+
/* active threads? */
if( rw->ltrw_r_active > 0 || rw->ltrw_w_active > 0) {
ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
ldap_pvt_thread_cond_destroy( &rw->ltrw_read );
ldap_pvt_thread_cond_destroy( &rw->ltrw_write );
+ LDAP_FREE(rw);
+ *rwlock = NULL;
return 0;
}
-int ldap_pvt_thread_rdwr_rlock( ldap_pvt_thread_rdwr_t *rw )
+int ldap_pvt_thread_rdwr_rlock( ldap_pvt_thread_rdwr_t *rwlock )
{
+ struct ldap_int_thread_rdwr_s *rw;
+
+ assert( rwlock != NULL );
+ rw = *rwlock;
+
assert( rw != NULL );
assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
+ assert( rw->ltrw_w_active >= 0 );
+ assert( rw->ltrw_w_wait >= 0 );
+ assert( rw->ltrw_r_active >= 0 );
+ assert( rw->ltrw_r_wait >= 0 );
+
if( rw->ltrw_w_active > 0 ) {
/* writer is active */
} while( rw->ltrw_w_active > 0 );
rw->ltrw_r_wait--;
+ assert( rw->ltrw_r_wait >= 0 );
}
+#ifdef LDAP_RDWR_DEBUG
+ if( rw->ltrw_r_active < MAX_READERS )
+ rw->ltrw_readers[rw->ltrw_r_active] = ldap_pvt_thread_self();
+ else
+ rw->ltrw_more_readers = 1;
+#endif
rw->ltrw_r_active++;
+
ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
return 0;
}
-int ldap_pvt_thread_rdwr_rtrylock( ldap_pvt_thread_rdwr_t *rw )
+int ldap_pvt_thread_rdwr_rtrylock( ldap_pvt_thread_rdwr_t *rwlock )
{
+ struct ldap_int_thread_rdwr_s *rw;
+
+ assert( rwlock != NULL );
+ rw = *rwlock;
+
assert( rw != NULL );
assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
+ assert( rw->ltrw_w_active >= 0 );
+ assert( rw->ltrw_w_wait >= 0 );
+ assert( rw->ltrw_r_active >= 0 );
+ assert( rw->ltrw_r_wait >= 0 );
+
if( rw->ltrw_w_active > 0) {
ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
return LDAP_PVT_THREAD_EBUSY;
}
+#ifdef LDAP_RDWR_DEBUG
+ if( rw->ltrw_r_active < MAX_READERS )
+ rw->ltrw_readers[rw->ltrw_r_active] = ldap_pvt_thread_self();
+ else
+ rw->ltrw_more_readers = 1;
+#endif
rw->ltrw_r_active++;
ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
return 0;
}
-int ldap_pvt_thread_rdwr_runlock( ldap_pvt_thread_rdwr_t *rw )
+int ldap_pvt_thread_rdwr_runlock( ldap_pvt_thread_rdwr_t *rwlock )
{
+ struct ldap_int_thread_rdwr_s *rw;
+
+ assert( rwlock != NULL );
+ rw = *rwlock;
+
assert( rw != NULL );
assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
rw->ltrw_r_active--;
+#ifdef LDAP_RDWR_DEBUG
+ /* Remove us from the list of readers */
+ {
+ ldap_pvt_thread_t self = ldap_pvt_thread_self();
+ int i, j;
+ for( i = j = rw->ltrw_r_active; i >= 0; i--) {
+ if (rw->ltrw_readers[i] == self) {
+ rw->ltrw_readers[i] = rw->ltrw_readers[j];
+ rw->ltrw_readers[j] = 0;
+ break;
+ }
+ }
+ if( !rw->ltrw_more_readers )
+ assert( i >= 0 );
+ else if( j == 0 )
+ rw->ltrw_more_readers = 0;
+ }
+#endif
+
+ assert( rw->ltrw_w_active >= 0 );
+ assert( rw->ltrw_w_wait >= 0 );
+ assert( rw->ltrw_r_active >= 0 );
+ assert( rw->ltrw_r_wait >= 0 );
if (rw->ltrw_r_active == 0 && rw->ltrw_w_wait > 0 ) {
ldap_pvt_thread_cond_signal( &rw->ltrw_write );
return 0;
}
-int ldap_pvt_thread_rdwr_wlock( ldap_pvt_thread_rdwr_t *rw )
+int ldap_pvt_thread_rdwr_wlock( ldap_pvt_thread_rdwr_t *rwlock )
{
+ struct ldap_int_thread_rdwr_s *rw;
+
+ assert( rwlock != NULL );
+ rw = *rwlock;
+
assert( rw != NULL );
assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
+ assert( rw->ltrw_w_active >= 0 );
+ assert( rw->ltrw_w_wait >= 0 );
+ assert( rw->ltrw_r_active >= 0 );
+ assert( rw->ltrw_r_wait >= 0 );
+
if ( rw->ltrw_w_active > 0 || rw->ltrw_r_active > 0 ) {
rw->ltrw_w_wait++;
} while ( rw->ltrw_w_active > 0 || rw->ltrw_r_active > 0 );
rw->ltrw_w_wait--;
+ assert( rw->ltrw_w_wait >= 0 );
}
+#ifdef LDAP_RDWR_DEBUG
+ rw->ltrw_writer = ldap_pvt_thread_self();
+#endif
rw->ltrw_w_active++;
ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
return 0;
}
-int ldap_pvt_thread_rdwr_wtrylock( ldap_pvt_thread_rdwr_t *rw )
+int ldap_pvt_thread_rdwr_wtrylock( ldap_pvt_thread_rdwr_t *rwlock )
{
+ struct ldap_int_thread_rdwr_s *rw;
+
+ assert( rwlock != NULL );
+ rw = *rwlock;
+
assert( rw != NULL );
assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
ldap_pvt_thread_mutex_lock( &rw->ltrw_mutex );
+ assert( rw->ltrw_w_active >= 0 );
+ assert( rw->ltrw_w_wait >= 0 );
+ assert( rw->ltrw_r_active >= 0 );
+ assert( rw->ltrw_r_wait >= 0 );
+
if ( rw->ltrw_w_active > 0 || rw->ltrw_r_active > 0 ) {
ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
return LDAP_PVT_THREAD_EBUSY;
}
+#ifdef LDAP_RDWR_DEBUG
+ rw->ltrw_writer = ldap_pvt_thread_self();
+#endif
rw->ltrw_w_active++;
ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
return 0;
}
-int ldap_pvt_thread_rdwr_wunlock( ldap_pvt_thread_rdwr_t *rw )
+int ldap_pvt_thread_rdwr_wunlock( ldap_pvt_thread_rdwr_t *rwlock )
{
+ struct ldap_int_thread_rdwr_s *rw;
+
+ assert( rwlock != NULL );
+ rw = *rwlock;
+
assert( rw != NULL );
assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
rw->ltrw_w_active--;
+ assert( rw->ltrw_w_active >= 0 );
+ assert( rw->ltrw_w_wait >= 0 );
+ assert( rw->ltrw_r_active >= 0 );
+ assert( rw->ltrw_r_wait >= 0 );
+
if (rw->ltrw_r_wait > 0) {
ldap_pvt_thread_cond_broadcast( &rw->ltrw_read );
ldap_pvt_thread_cond_signal( &rw->ltrw_write );
}
+#ifdef LDAP_RDWR_DEBUG
+ assert( rw->ltrw_writer == ldap_pvt_thread_self() );
+ rw->ltrw_writer = 0;
+#endif
ldap_pvt_thread_mutex_unlock( &rw->ltrw_mutex );
return 0;
* a lock are caught.
*/
-int ldap_pvt_thread_rdwr_readers(ldap_pvt_thread_rdwr_t *rw)
+int ldap_pvt_thread_rdwr_readers(ldap_pvt_thread_rdwr_t *rwlock)
{
+ struct ldap_int_thread_rdwr_s *rw;
+
+ assert( rwlock != NULL );
+ rw = *rwlock;
+
assert( rw != NULL );
assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
+ assert( rw->ltrw_w_active >= 0 );
+ assert( rw->ltrw_w_wait >= 0 );
+ assert( rw->ltrw_r_active >= 0 );
+ assert( rw->ltrw_r_wait >= 0 );
return( rw->ltrw_r_active );
}
-int ldap_pvt_thread_rdwr_writers(ldap_pvt_thread_rdwr_t *rw)
+int ldap_pvt_thread_rdwr_writers(ldap_pvt_thread_rdwr_t *rwlock)
{
+ struct ldap_int_thread_rdwr_s *rw;
+
+ assert( rwlock != NULL );
+ rw = *rwlock;
+
assert( rw != NULL );
assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
+ assert( rw->ltrw_w_active >= 0 );
+ assert( rw->ltrw_w_wait >= 0 );
+ assert( rw->ltrw_r_active >= 0 );
+ assert( rw->ltrw_r_wait >= 0 );
return( rw->ltrw_w_active );
}
-int ldap_pvt_thread_rdwr_active(ldap_pvt_thread_rdwr_t *rw)
+int ldap_pvt_thread_rdwr_active(ldap_pvt_thread_rdwr_t *rwlock)
{
+ struct ldap_int_thread_rdwr_s *rw;
+
+ assert( rwlock != NULL );
+ rw = *rwlock;
+
assert( rw != NULL );
assert( rw->ltrw_valid == LDAP_PVT_THREAD_RDWR_VALID );
+ assert( rw->ltrw_w_active >= 0 );
+ assert( rw->ltrw_w_wait >= 0 );
+ assert( rw->ltrw_r_active >= 0 );
+ assert( rw->ltrw_r_wait >= 0 );
- return(ldap_pvt_thread_rdwr_readers(rw) +
- ldap_pvt_thread_rdwr_writers(rw));
+ return(ldap_pvt_thread_rdwr_readers(rwlock) +
+ ldap_pvt_thread_rdwr_writers(rwlock));
}
-#endif /* LDAP_DEBUG */
+#endif /* LDAP_RDWR_DEBUG */
#endif /* LDAP_THREAD_HAVE_RDWR */
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