From: Jong Hyuk Choi <jongchoi@openldap.org>
Date: Fri, 31 May 2002 20:49:19 +0000 (+0000)
Subject: redesign of back-bdb locking :
X-Git-Tag: OPENLDAP_REL_ENG_2_MP~34
X-Git-Url: https://git.sur5r.net/?a=commitdiff_plain;h=7341dc5db656b33d6dfe86bce5a00c1328809caa;p=openldap

redesign of back-bdb locking :
cache entry is locked by Berkeley DB lock primitives.
---

diff --git a/servers/slapd/back-bdb/add.c b/servers/slapd/back-bdb/add.c
index b7cc3e70ef..303ed63a35 100644
--- a/servers/slapd/back-bdb/add.c
+++ b/servers/slapd/back-bdb/add.c
@@ -23,7 +23,7 @@ bdb_add(
 	struct bdb_info *bdb = (struct bdb_info *) be->be_private;
 	struct berval	pdn;
 	Entry		*p = NULL;
-	int			rc; 
+	int		rc, ret; 
 	const char	*text;
 	char textbuf[SLAP_TEXT_BUFLEN];
 	size_t textlen = sizeof textbuf;
@@ -33,6 +33,8 @@ bdb_add(
 #ifdef BDB_SUBENTRIES
 	int subentry;
 #endif
+	u_int32_t	locker;
+	DB_LOCK		lock;
 #if 0
 	u_int32_t	lockid;
 	DB_LOCK		lock;
@@ -108,6 +110,8 @@ retry:	/* transaction retry */
 		text = "internal error";
 		goto return_results;
 	}
+
+	locker = TXN_ID ( ltid );
 #if 0
 	lockid = TXN_ID( ltid );
 #endif
@@ -142,7 +146,7 @@ retry:	/* transaction retry */
 #endif
 
 		/* get parent */
-		rc = bdb_dn2entry_r( be, ltid, &pdn, &p, &matched, 0 );
+		rc = bdb_dn2entry_r( be, ltid, &pdn, &p, &matched, 0, locker, &lock );
 
 		switch( rc ) {
 		case 0:
@@ -169,7 +173,7 @@ retry:	/* transaction retry */
 				refs = is_entry_referral( matched )
 					? get_entry_referrals( be, conn, op, matched )
 					: NULL;
-				bdb_cache_return_entry_r(&bdb->bi_cache, matched);
+				bdb_cache_return_entry_r(bdb->bi_dbenv, &bdb->bi_cache, matched, &lock);
 				matched = NULL;
 
 			} else {
@@ -200,7 +204,7 @@ retry:	/* transaction retry */
 		case DB_LOCK_DEADLOCK:
 		case DB_LOCK_NOTGRANTED:
 			/* free parent and reader lock */
-			bdb_cache_return_entry_r( &bdb->bi_cache, p );
+			bdb_cache_return_entry_r( bdb->bi_dbenv, &bdb->bi_cache, p, &lock );
 			p = NULL;
 			goto retry;
 		}
@@ -262,7 +266,7 @@ retry:	/* transaction retry */
 				matched_dn, NULL, refs, NULL );
 
 			ber_bvarray_free( refs );
-			bdb_cache_return_entry_r( &bdb->bi_cache, p );
+			bdb_cache_return_entry_r( bdb->bi_dbenv, &bdb->bi_cache, p, &lock );
 			p = NULL;
 			goto done;
 		}
@@ -275,7 +279,7 @@ retry:	/* transaction retry */
 #endif
 
 		/* free parent and reader lock */
-		bdb_cache_return_entry_r( &bdb->bi_cache, p );
+		bdb_cache_return_entry_r( bdb->bi_dbenv, &bdb->bi_cache, p, &lock );
 		p = NULL;
 
 	} else {
@@ -430,9 +434,22 @@ retry:	/* transaction retry */
 			text = "txn_prepare failed";
 
 		} else {
+			ret = bdb_cache_add_entry_rw(bdb->bi_dbenv, &bdb->bi_cache, e, CACHE_WRITE_LOCK, locker, &lock);
+#if 0
 			if ( bdb_cache_add_entry_rw(&bdb->bi_cache,
 				e, CACHE_WRITE_LOCK) != 0 )
-			{
+#endif
+			switch ( ret ) {
+			case 0:
+				break;
+			case DB_LOCK_DEADLOCK:
+			case DB_LOCK_NOTGRANTED:
+				goto retry;
+			default:
+				ret = LDAP_OTHER;
+			}
+
+			if ( ret ) {
 				if(( rc=TXN_ABORT( ltid )) != 0 ) {
 					text = "cache add & txn_abort failed";
 				} else {
diff --git a/servers/slapd/back-bdb/attribute.c b/servers/slapd/back-bdb/attribute.c
index 38203b994d..1277f02561 100644
--- a/servers/slapd/back-bdb/attribute.c
+++ b/servers/slapd/back-bdb/attribute.c
@@ -39,6 +39,9 @@ bdb_attribute(
 	const char *entry_at_name = entry_at->ad_cname.bv_val;
 	AccessControlState acl_state = ACL_STATE_INIT;
 
+	u_int32_t	locker;
+	DB_LOCK		lock;
+
 #ifdef NEW_LOGGING
 	LDAP_LOG(( "backend", LDAP_LEVEL_ARGS,
 		"bdb_attribute: gr dn: \"%s\"\n", entry_ndn->bv_val ));
@@ -65,6 +68,11 @@ bdb_attribute(
 		txn = boi->boi_txn;
 	}
 
+	if ( txn != NULL )
+		locker = TXN_ID ( txn );
+	else
+		LOCK_ID ( bdb->bi_dbenv, &locker );
+
 	if (target != NULL && dn_match(&target->e_nname, entry_ndn)) {
 		/* we already have a LOCKED copy of the entry */
 		e = target;
@@ -80,16 +88,23 @@ bdb_attribute(
 
 
 	} else {
+dn2entry_retry:
 		/* can we find entry */
-		rc = bdb_dn2entry_r( be, NULL, entry_ndn, &e, NULL, 0 );
+		rc = bdb_dn2entry_r( be, NULL, entry_ndn, &e, NULL, 0, locker, &lock );
 		switch( rc ) {
 		case DB_NOTFOUND:
 		case 0:
 			break;
+		case DB_LOCK_DEADLOCK:
+		case DB_LOCK_NOTGRANTED:
+			goto dn2entry_retry;
 		default:
 			if( txn != NULL ) {
 				boi->boi_err = rc;
 			}
+			else {
+				LOCK_ID_FREE( bdb->bi_dbenv, locker );
+			}
 			return (rc != LDAP_BUSY) ? LDAP_OTHER : LDAP_BUSY;
 		}
 		if (e == NULL) {
@@ -102,6 +117,9 @@ bdb_attribute(
 				"=> bdb_attribute: cannot find entry: \"%s\"\n",
 					entry_ndn->bv_val, 0, 0 ); 
 #endif
+			if ( txn == NULL ) {
+				LOCK_ID_FREE( bdb->bi_dbenv, locker );
+			}
 			return LDAP_NO_SUCH_OBJECT; 
 		}
 		
@@ -205,7 +223,11 @@ bdb_attribute(
 return_results:
 	if( target != e ) {
 		/* free entry */
-		bdb_cache_return_entry_r(&bdb->bi_cache, e);
+		bdb_cache_return_entry_r(bdb->bi_dbenv, &bdb->bi_cache, e, &lock);
+	}
+
+	if ( txn == NULL ) {
+		LOCK_ID_FREE( bdb->bi_dbenv, locker );
 	}
 
 #ifdef NEW_LOGGING
diff --git a/servers/slapd/back-bdb/back-bdb.h b/servers/slapd/back-bdb/back-bdb.h
index be89b98bf3..784bbc89aa 100644
--- a/servers/slapd/back-bdb/back-bdb.h
+++ b/servers/slapd/back-bdb/back-bdb.h
@@ -146,21 +146,27 @@ struct bdb_op_info {
 #if DB_VERSION_MAJOR < 4
 #define LOCK_DETECT(env,f,t,a)		lock_detect(env, f, t, a)
 #define LOCK_GET(env,i,f,o,m,l)		lock_get(env, i, f, o, m, l)
+#define LOCK_PUT(env,l)			lock_put(env, l)
 #define TXN_CHECKPOINT(env,k,m,f)	txn_checkpoint(env, k, m, f)
 #define TXN_BEGIN(env,p,t,f)		txn_begin((env), p, t, f)
 #define TXN_PREPARE(txn,gid)		txn_prepare((txn), (gid))
 #define TXN_COMMIT(txn,f)			txn_commit((txn), (f))
 #define	TXN_ABORT(txn)				txn_abort((txn))
 #define TXN_ID(txn)					txn_id(txn)
+#define LOCK_ID(env, locker)		lock_id(env, locker)
+#define LOCK_ID_FREE(env, locker)	lock_id_free(env, locker)
 #else
 #define LOCK_DETECT(env,f,t,a)		(env)->lock_detect(env, f, t, a)
 #define LOCK_GET(env,i,f,o,m,l)		(env)->lock_get(env, i, f, o, m, l)
+#define LOCK_PUT(env,l)			(env)->lock_put(env, l)
 #define TXN_CHECKPOINT(env,k,m,f)	(env)->txn_checkpoint(env, k, m, f)
 #define TXN_BEGIN(env,p,t,f)		(env)->txn_begin((env), p, t, f)
 #define TXN_PREPARE(txn,g)			(txn)->prepare((txn), (g))
 #define TXN_COMMIT(txn,f)			(txn)->commit((txn), (f))
 #define TXN_ABORT(txn)				(txn)->abort((txn))
 #define TXN_ID(txn)					(txn)->id(txn)
+#define LOCK_ID(env, locker)		(env)->lock_id(env, locker)
+#define LOCK_ID_FREE(env, locker)	(env)->lock_id_free(env, locker)
 #endif
 
 LDAP_END_DECL
diff --git a/servers/slapd/back-bdb/bind.c b/servers/slapd/back-bdb/bind.c
index ad1bcfe3bb..be64c5b6a8 100644
--- a/servers/slapd/back-bdb/bind.c
+++ b/servers/slapd/back-bdb/bind.c
@@ -40,14 +40,20 @@ bdb_bind(
 
 	AttributeDescription *password = slap_schema.si_ad_userPassword;
 
+	u_int32_t	locker;
+	DB_LOCK		lock;
+
 #ifdef NEW_LOGGING
 	LDAP_LOG (( "bind", LDAP_LEVEL_ARGS, "==> bdb_bind: dn: %s\n", dn->bv_val ));
 #else
 	Debug( LDAP_DEBUG_ARGS, "==> bdb_bind: dn: %s\n", dn->bv_val, 0, 0);
 #endif
 
+	LOCK_ID(bdb->bi_dbenv, &locker);
+
+dn2entry_retry:
 	/* get entry */
-	rc = bdb_dn2entry_r( be, NULL, ndn, &e, &matched, 0 );
+	rc = bdb_dn2entry_r( be, NULL, ndn, &e, &matched, 0, locker, &lock );
 
 	switch(rc) {
 	case DB_NOTFOUND:
@@ -56,10 +62,15 @@ bdb_bind(
 	case LDAP_BUSY:
 		send_ldap_result( conn, op, LDAP_BUSY,
 			NULL, "ldap server busy", NULL, NULL );
+		LOCK_ID_FREE(bdb->bi_dbenv, locker);
 		return LDAP_BUSY;
+	case DB_LOCK_DEADLOCK:
+	case DB_LOCK_NOTGRANTED:
+		goto dn2entry_retry;
 	default:
 		send_ldap_result( conn, op, rc=LDAP_OTHER,
 			NULL, "internal error", NULL, NULL );
+		LOCK_ID_FREE(bdb->bi_dbenv, locker);
 		return rc;
 	}
 
@@ -75,7 +86,7 @@ bdb_bind(
 				? get_entry_referrals( be, conn, op, matched )
 				: NULL;
 
-			bdb_cache_return_entry_r( &bdb->bi_cache, matched );
+			bdb_cache_return_entry_r( bdb->bi_dbenv, &bdb->bi_cache, matched, &lock );
 			matched = NULL;
 
 		} else {
@@ -108,6 +119,8 @@ bdb_bind(
 				NULL, NULL, NULL, NULL );
 		}
 
+		LOCK_ID_FREE(bdb->bi_dbenv, locker);
+
 		ber_bvarray_free( refs );
 		free( matched_dn );
 
@@ -274,9 +287,11 @@ bdb_bind(
 done:
 	/* free entry and reader lock */
 	if( e != NULL ) {
-		bdb_cache_return_entry_r( &bdb->bi_cache, e );
+		bdb_cache_return_entry_r( bdb->bi_dbenv, &bdb->bi_cache, e, &lock );
 	}
 
+	LOCK_ID_FREE(bdb->bi_dbenv, locker);
+
 	/* front end with send result on success (rc==0) */
 	return rc;
 }
diff --git a/servers/slapd/back-bdb/cache.c b/servers/slapd/back-bdb/cache.c
index 5038db4bc7..35d5a5720d 100644
--- a/servers/slapd/back-bdb/cache.c
+++ b/servers/slapd/back-bdb/cache.c
@@ -132,6 +132,36 @@ bdb_cache_entry_private_init( Entry *e )
 	return 0;
 }
 
+int
+bdb_cache_entry_db_lock
+( DB_ENV *env, u_int32_t locker, Entry *e, int rw, u_int32_t flags, DB_LOCK *lock )
+{
+	int       rc;
+	DBT       lockobj;
+	int       db_rw;
+
+	if (rw)
+		db_rw = DB_LOCK_WRITE;
+	else
+		db_rw = DB_LOCK_READ;
+
+	lockobj.data = e->e_nname.bv_val;
+	lockobj.size = e->e_nname.bv_len;
+	rc = LOCK_GET(env, locker, flags | DB_LOCK_NOWAIT,
+					&lockobj, db_rw, lock);
+	return rc;
+}
+
+int
+bdb_cache_entry_db_unlock
+( DB_ENV *env, DB_LOCK *lock )
+{
+	int rc;
+
+	rc = LOCK_PUT ( env, lock );
+	return rc;
+}
+
 /*
  * marks an entry in CREATING state as committed, so it is really returned
  * to the cache. Otherwise an entry in CREATING state is removed.
@@ -162,8 +192,9 @@ bdb_cache_entry_private_destroy( Entry *e )
 }
 
 void
-bdb_cache_return_entry_rw( Cache *cache, Entry *e, int rw )
+bdb_unlocked_cache_return_entry_rw( Cache *cache, Entry *e, int rw )
 {
+
 	ID id;
 	int refcnt, freeit = 1;
 
@@ -172,7 +203,112 @@ bdb_cache_return_entry_rw( Cache *cache, Entry *e, int rw )
 
 	assert( e->e_private );
 
+#if 0
 	bdb_cache_entry_rdwr_unlock(e, rw);
+#endif
+
+	id = e->e_id;
+	refcnt = --BEI(e)->bei_refcnt;
+
+	/*
+	 * if the entry is returned when in CREATING state, it is deleted
+	 * but not freed because it may belong to someone else (do_add,
+	 * for instance)
+	 */
+	if (  BEI(e)->bei_state == CACHE_ENTRY_CREATING ) {
+		/* set lru mutex */
+		ldap_pvt_thread_mutex_lock( &cache->lru_mutex );
+		bdb_cache_delete_entry_internal( cache, e );
+		/* free lru mutex */
+		ldap_pvt_thread_mutex_unlock( &cache->lru_mutex );
+		freeit = 0;
+		/* now the entry is in DELETED state */
+	}
+
+	if ( BEI(e)->bei_state == CACHE_ENTRY_COMMITTED ) {
+		BEI(e)->bei_state = CACHE_ENTRY_READY;
+
+		/* free cache write lock */
+		ldap_pvt_thread_rdwr_wunlock( &cache->c_rwlock );
+
+#ifdef NEW_LOGGING
+		LDAP_LOG(( "cache", LDAP_LEVEL_DETAIL1,
+			   "bdb_cache_return_entry_rw: return (%ld):%s, refcnt=%d\n",
+			   id, rw ? "w" : "r", refcnt ));
+#else
+		Debug( LDAP_DEBUG_TRACE,
+			"====> bdb_cache_return_entry_%s( %ld ): created (%d)\n",
+			rw ? "w" : "r", id, refcnt );
+#endif
+
+
+	} else if ( BEI(e)->bei_state == CACHE_ENTRY_DELETED ) {
+		if( refcnt > 0 ) {
+			/* free cache write lock */
+			ldap_pvt_thread_rdwr_wunlock( &cache->c_rwlock );
+
+#ifdef NEW_LOGGING
+			LDAP_LOG(( "cache", LDAP_LEVEL_DETAIL1,
+				   "bdb_cache_return_entry_rw: %ld, delete pending (%d).\n",
+				   id, refcnt ));
+#else
+			Debug( LDAP_DEBUG_TRACE,
+				"====> bdb_cache_return_entry_%s( %ld ): delete pending (%d)\n",
+				rw ? "w" : "r", id, refcnt );
+#endif
+
+		} else {
+			bdb_cache_entry_private_destroy( e );
+			if ( freeit ) {
+				bdb_entry_return( e );
+			}
+
+			/* free cache write lock */
+			ldap_pvt_thread_rdwr_wunlock( &cache->c_rwlock );
+
+#ifdef NEW_LOGGING
+			LDAP_LOG(( "cache", LDAP_LEVEL_DETAIL1,
+				   "bdb_cache_return_entry_rw: (%ld): deleted (%d)\n",
+				   id, refcnt ));
+#else
+			Debug( LDAP_DEBUG_TRACE,
+				"====> bdb_cache_return_entry_%s( %ld ): deleted (%d)\n",
+				rw ? "w" : "r", id, refcnt );
+#endif
+		}
+
+	} else {
+		/* free cache write lock */
+		ldap_pvt_thread_rdwr_wunlock( &cache->c_rwlock );
+
+#ifdef NEW_LOGGING
+		LDAP_LOG(( "cache", LDAP_LEVEL_DETAIL1,
+			   "bdb_cache_return_entry_rw: ID %ld:%s returned (%d)\n",
+			   id, rw ? "w": "r", refcnt ));
+#else
+		Debug( LDAP_DEBUG_TRACE,
+			"====> bdb_cache_return_entry_%s( %ld ): returned (%d)\n",
+			rw ? "w" : "r", id, refcnt);
+#endif
+	}
+}
+
+void
+bdb_cache_return_entry_rw
+( DB_ENV *env, Cache *cache, Entry *e, int rw, DB_LOCK *lock )
+{
+	ID id;
+	int refcnt, freeit = 1;
+
+	/* set cache write lock */
+	ldap_pvt_thread_rdwr_wlock( &cache->c_rwlock );
+
+	assert( e->e_private );
+
+	bdb_cache_entry_db_unlock( env, lock );
+#if 0
+	bdb_cache_entry_rdwr_unlock(e, rw);
+#endif
 
 	id = e->e_id;
 	refcnt = --BEI(e)->bei_refcnt;
@@ -290,12 +426,16 @@ bdb_cache_return_entry_rw( Cache *cache, Entry *e, int rw )
  * returns:	0	entry has been created and locked
  *		1	entry already existed
  *		-1	something bad happened
+ *             other    Berkeley DB locking error code
  */
 int
 bdb_cache_add_entry_rw(
+    DB_ENV	*env,
     Cache	*cache,
     Entry	*e,
-    int		rw
+    int		rw,
+    u_int32_t	locker,
+    DB_LOCK	*lock
 )
 {
 	int	i, rc;
@@ -385,7 +525,37 @@ bdb_cache_add_entry_rw(
 		return( -1 );
 	}
 
-	bdb_cache_entry_rdwr_lock( e, rw );
+	rc = bdb_cache_entry_db_lock( env, locker, e, rw, 0, lock );
+	switch ( rc ) {
+	case 0 :
+		break;
+	case DB_LOCK_DEADLOCK :
+	case DB_LOCK_NOTGRANTED :
+		/* undo avl changes immediately */
+		if ( avl_delete( &cache->c_idtree, (caddr_t) e,
+			(AVL_CMP) entry_id_cmp ) == NULL ) {
+#ifdef NEW_LOGGING
+			LDAP_LOG(( "cache", LDAP_LEVEL_INFO,
+				"bdb_cache_add_entry: can't delete (%s) from cache.\n", e->e_dn ));
+#else
+			Debug( LDAP_DEBUG_ANY, "====> can't delete from id cache\n", 0, 0, 0 );
+#endif
+		}
+		if ( avl_delete( &cache->c_dntree, (caddr_t) e,
+				(AVL_CMP) entry_dn_cmp ) == NULL ) {
+#ifdef NEW_LOGGING
+			LDAP_LOG(( "cache", LDAP_LEVEL_INFO,
+					"bdb_cache_add_entry: can't delete (%s) from cache.\n", e->e_dn ));
+#else
+			Debug( LDAP_DEBUG_ANY, "====> can't delete from dn cache\n", 0, 0, 0 );
+#endif
+		}
+		/* fall through */
+	default :
+		bdb_cache_entry_private_destroy(e);
+		ldap_pvt_thread_rdwr_wunlock( &cache->c_rwlock );
+		return rc;
+	}
 
 	/* put the entry into 'CREATING' state */
 	/* will be marked after when entry is returned */
@@ -661,14 +831,18 @@ try_again:
 
 Entry *
 bdb_cache_find_entry_id(
+	DB_ENV	*env,
 	Cache	*cache,
 	ID				id,
-	int				rw
+	int				rw,
+	u_int32_t	locker,
+	DB_LOCK		*lock
 )
 {
 	Entry	e;
 	Entry	*ep;
 	int	count = 0;
+	int	rc;
 
 	e.e_id = id;
 
@@ -715,7 +889,13 @@ try_again:
 		}
 
 		/* acquire reader lock */
+		rc = bdb_cache_entry_db_lock ( env, locker, ep, rw, 0, lock );
+
+#if 0
 		if ( bdb_cache_entry_rdwr_trylock(ep, rw) == LDAP_PVT_THREAD_EBUSY ) {
+#endif
+
+		if ( rc ) { /* will be changed to retry beyond threshold */
 			/* could not acquire entry lock...
 			 * owner cannot free as we have the cache locked.
 			 * so, unlock the cache, yield, and try again.
@@ -732,6 +912,9 @@ try_again:
 			Debug(LDAP_DEBUG_TRACE,
 				"====> bdb_cache_find_entry_id( %ld ): %ld (busy) %d\n",
 				id, ep_id, state);
+			Debug(LDAP_DEBUG_TRACE,
+				"locker = %d\n",
+				locker, 0, 0);
 #endif
 
 			ldap_pvt_thread_yield();
diff --git a/servers/slapd/back-bdb/compare.c b/servers/slapd/back-bdb/compare.c
index e9c40dcbbc..ac799bb627 100644
--- a/servers/slapd/back-bdb/compare.c
+++ b/servers/slapd/back-bdb/compare.c
@@ -31,8 +31,14 @@ bdb_compare(
 	const char	*text = NULL;
 	int		manageDSAit = get_manageDSAit( op );
 
+	u_int32_t	locker;
+	DB_LOCK		lock;
+
+	LOCK_ID ( bdb->bi_dbenv, &locker );
+
+dn2entry_retry:
 	/* get entry */
-	rc = bdb_dn2entry_r( be, NULL, ndn, &e, &matched, 0 );
+	rc = bdb_dn2entry_r( be, NULL, ndn, &e, &matched, 0, locker, &lock );
 
 	switch( rc ) {
 	case DB_NOTFOUND:
@@ -41,6 +47,9 @@ bdb_compare(
 	case LDAP_BUSY:
 		text = "ldap server busy";
 		goto return_results;
+	case DB_LOCK_DEADLOCK:
+	case DB_LOCK_NOTGRANTED:
+		goto dn2entry_retry;
 	default:
 		rc = LDAP_OTHER;
 		text = "internal error";
@@ -56,7 +65,7 @@ bdb_compare(
 			refs = is_entry_referral( matched )
 				? get_entry_referrals( be, conn, op, matched )
 				: NULL;
-			bdb_cache_return_entry_r( &bdb->bi_cache, matched );
+			bdb_cache_return_entry_r( bdb->bi_dbenv, &bdb->bi_cache, matched, &lock );
 			matched = NULL;
 
 		} else {
@@ -125,8 +134,10 @@ return_results:
 done:
 	/* free entry */
 	if( e != NULL ) {
-		bdb_cache_return_entry_r( &bdb->bi_cache, e );
+		bdb_cache_return_entry_r( bdb->bi_dbenv, &bdb->bi_cache, e, &lock );
 	}
 
+	LOCK_ID_FREE ( bdb->bi_dbenv, locker );
+
 	return rc;
 }
diff --git a/servers/slapd/back-bdb/delete.c b/servers/slapd/back-bdb/delete.c
index dcaf399faf..9ded16580e 100644
--- a/servers/slapd/back-bdb/delete.c
+++ b/servers/slapd/back-bdb/delete.c
@@ -33,6 +33,9 @@ bdb_delete(
 	AttributeDescription *children = slap_schema.si_ad_children;
 	DB_TXN		*ltid = NULL;
 	struct bdb_op_info opinfo;
+
+	u_int32_t	locker;
+	DB_LOCK		lock;
 #if 0
 	u_int32_t	lockid;
 	DB_LOCK		lock;
@@ -49,7 +52,7 @@ bdb_delete(
 	if( 0 ) {
 retry:	/* transaction retry */
 		if( e != NULL ) {
-			bdb_cache_return_entry_w(&bdb->bi_cache, e);
+			bdb_cache_return_entry_w(bdb->bi_dbenv, &bdb->bi_cache, e, &lock);
 		}
 #ifdef NEW_LOGGING
 		LDAP_LOG (( "delete", LDAP_LEVEL_DETAIL1, 
@@ -87,6 +90,8 @@ retry:	/* transaction retry */
 		text = "internal error";
 		goto return_results;
 	}
+
+	locker = TXN_ID ( ltid );
 #if 0
 	lockid = TXN_ID( ltid );
 #endif
@@ -111,7 +116,7 @@ retry:	/* transaction retry */
 		}
 #endif
 		/* get parent */
-		rc = bdb_dn2entry_r( be, ltid, &pdn, &p, NULL, 0 );
+		rc = bdb_dn2entry_r( be, ltid, &pdn, &p, NULL, 0, locker, &lock );
 
 		switch( rc ) {
 		case 0:
@@ -147,7 +152,7 @@ retry:	/* transaction retry */
 		rc = access_allowed( be, conn, op, p,
 			children, NULL, ACL_WRITE, NULL );
 
-		bdb_cache_return_entry_r(&bdb->bi_cache, p);
+		bdb_cache_return_entry_r(bdb->bi_dbenv, &bdb->bi_cache, p, &lock);
 		p = NULL;
 
 		switch( opinfo.boi_err ) {
@@ -226,7 +231,7 @@ retry:	/* transaction retry */
 	}
 
 	/* get entry for read/modify/write */
-	rc = bdb_dn2entry_w( be, ltid, ndn, &e, &matched, DB_RMW );
+	rc = bdb_dn2entry_w( be, ltid, ndn, &e, &matched, DB_RMW, locker, &lock );
 
 	switch( rc ) {
 	case 0:
@@ -263,7 +268,7 @@ retry:	/* transaction retry */
 			refs = is_entry_referral( matched )
 				? get_entry_referrals( be, conn, op, matched )
 				: NULL;
-			bdb_cache_return_entry_r(&bdb->bi_cache, matched );
+			bdb_cache_return_entry_r(bdb->bi_dbenv, &bdb->bi_cache, matched, &lock );
 			matched = NULL;
 
 		} else {
@@ -465,7 +470,7 @@ return_results:
 done:
 	/* free entry */
 	if( e != NULL ) {
-		bdb_cache_return_entry_w(&bdb->bi_cache, e);
+		bdb_cache_return_entry_w(bdb->bi_dbenv, &bdb->bi_cache, e, &lock);
 	}
 
 	if( ltid != NULL ) {
diff --git a/servers/slapd/back-bdb/dn2entry.c b/servers/slapd/back-bdb/dn2entry.c
index 00cd9efed7..a6440536f7 100644
--- a/servers/slapd/back-bdb/dn2entry.c
+++ b/servers/slapd/back-bdb/dn2entry.c
@@ -25,7 +25,9 @@ bdb_dn2entry_rw(
 	Entry **e,
 	Entry **matched,
 	int flags,
-	int rw )
+	int rw,
+	u_int32_t locker,
+	DB_LOCK *lock )
 {
 	int rc;
 	ID		id, id2 = 0;
@@ -52,9 +54,9 @@ bdb_dn2entry_rw(
 	}
 
 	if( id2 == 0 ) {
-		rc = bdb_id2entry_rw( be, tid, id, e, rw );
+		rc = bdb_id2entry_rw( be, tid, id, e, rw, locker, lock );
 	} else {
-		rc = bdb_id2entry_r( be, tid, id2, matched);
+		rc = bdb_id2entry_r( be, tid, id2, matched, locker, lock );
 	}
 
 	return rc;
diff --git a/servers/slapd/back-bdb/group.c b/servers/slapd/back-bdb/group.c
index 2000de5209..6c2cdf1133 100644
--- a/servers/slapd/back-bdb/group.c
+++ b/servers/slapd/back-bdb/group.c
@@ -44,6 +44,9 @@ bdb_group(
 	const char *group_oc_name = NULL;
 	const char *group_at_name = group_at->ad_cname.bv_val;
 
+	u_int32_t	locker;
+	DB_LOCK		lock;
+
 	if( group_oc->soc_names && group_oc->soc_names[0] ) {
 		group_oc_name = group_oc->soc_names[0];
 	} else {
@@ -76,6 +79,11 @@ bdb_group(
 		txn = boi->boi_txn;
 	}
 
+	if ( txn )
+		locker = TXN_ID( txn );
+	else
+		LOCK_ID ( bdb->bi_dbenv, &locker );
+
 	if (dn_match(&target->e_name, gr_ndn)) {
 		/* we already have a LOCKED copy of the entry */
 		e = target;
@@ -88,12 +96,18 @@ bdb_group(
 			gr_ndn->bv_val, 0, 0 );
 #endif
 	} else {
+dn2entry_retry:
 		/* can we find group entry */
-		rc = bdb_dn2entry_r( be, NULL, gr_ndn, &e, NULL, 0 ); 
+		rc = bdb_dn2entry_r( be, NULL, gr_ndn, &e, NULL, 0, locker, &lock ); 
 		if( rc ) {
+			if ( rc == DB_LOCK_DEADLOCK || rc == DB_LOCK_NOTGRANTED )
+				goto dn2entry_retry;
 			if( txn ) {
 				boi->boi_err = rc;
 			}
+			else {
+				LOCK_ID_FREE ( bdb->bi_dbenv, locker );
+			}
 			return( 1 );
 		}
 		if (e == NULL) {
@@ -106,6 +120,9 @@ bdb_group(
 				"=> bdb_group: cannot find group: \"%s\"\n",
 					gr_ndn->bv_val, 0, 0 ); 
 #endif
+			if ( txn == NULL ) {
+				LOCK_ID_FREE ( bdb->bi_dbenv, locker );
+			}
 			return( 1 );
 		}
 #ifdef NEW_LOGGING
@@ -211,7 +228,11 @@ bdb_group(
 return_results:
 	if( target != e ) {
 		/* free entry */
-		bdb_cache_return_entry_r( &bdb->bi_cache, e );
+		bdb_cache_return_entry_r( bdb->bi_dbenv, &bdb->bi_cache, e, &lock );
+	}
+
+	if ( txn == NULL ) {
+		LOCK_ID_FREE ( bdb->bi_dbenv, locker );
 	}
 
 #ifdef NEW_LOGGING
diff --git a/servers/slapd/back-bdb/id2entry.c b/servers/slapd/back-bdb/id2entry.c
index 10ec1637a5..0a841cab21 100644
--- a/servers/slapd/back-bdb/id2entry.c
+++ b/servers/slapd/back-bdb/id2entry.c
@@ -80,13 +80,15 @@ int bdb_id2entry_rw(
 	DB_TXN *tid,
 	ID id,
 	Entry **e,
-	int rw )
+	int rw,
+	u_int32_t locker,
+	DB_LOCK *lock )
 {
 	struct bdb_info *bdb = (struct bdb_info *) be->be_private;
 	DB *db = bdb->bi_id2entry->bdi_db;
 	DBT key, data;
 	struct berval bv;
-	int rc = 0;
+	int rc = 0, ret = 0;
 
 	*e = NULL;
 
@@ -97,7 +99,7 @@ int bdb_id2entry_rw(
 	DBTzero( &data );
 	data.flags = DB_DBT_MALLOC;
 
-	if ((*e = bdb_cache_find_entry_id(&bdb->bi_cache, id, rw)) != NULL) {
+	if ((*e = bdb_cache_find_entry_id(bdb->bi_dbenv, &bdb->bi_cache, id, rw, locker, lock)) != NULL) {
 		return 0;
 	}
 
@@ -121,24 +123,36 @@ int bdb_id2entry_rw(
 		ch_free( data.data );
 	}
 
-	while (rc == 0 && bdb_cache_add_entry_rw(&bdb->bi_cache, *e, rw) != 0) {
-		Entry *ee;
-		int add_loop_cnt = 0;
-		if ( (*e)->e_private != NULL ) {
-			free ((*e)->e_private);
-		}
-		(*e)->e_private = NULL;
-		if ( (ee = bdb_cache_find_entry_id
-				(&bdb->bi_cache, id, rw) ) != NULL) {
-			bdb_entry_return ( *e );
-			*e = ee;
-			return 0;
+	if ( rc == 0 ) {
+		ret = bdb_cache_add_entry_rw( bdb->bi_dbenv,
+				&bdb->bi_cache, *e, rw, locker, lock);
+		while ( ret == 1 || ret == -1 ) {
+			Entry *ee;
+			int add_loop_cnt = 0;
+			if ( (*e)->e_private != NULL ) {
+				free ((*e)->e_private);
+			}
+			(*e)->e_private = NULL;
+			if ( (ee = bdb_cache_find_entry_id
+					(bdb->bi_dbenv, &bdb->bi_cache, id, rw, locker, lock) ) != NULL) {
+				bdb_entry_return ( *e );
+				*e = ee;
+				return 0;
+			}
+			if ( ++add_loop_cnt == BDB_MAX_ADD_LOOP ) {
+				bdb_entry_return ( *e );
+				*e = NULL;
+				return LDAP_BUSY;
+			}
 		}
-		if ( ++add_loop_cnt == BDB_MAX_ADD_LOOP ) {
-			bdb_entry_return ( *e );
+		if ( ret != 0 ) {
+			if ( (*e)->e_private != NULL )
+				free ( (*e)->e_private );
+			bdb_entry_return( *e );
 			*e = NULL;
-			return LDAP_BUSY;
+			ch_free( data.data );
 		}
+		rc = ret;
 	}
 
 #ifdef BDB_HIER
@@ -232,7 +246,7 @@ int bdb_entry_release(
  
 	if ( slapMode == SLAP_SERVER_MODE ) {
 		/* free entry and reader or writer lock */
-		bdb_cache_return_entry_rw( &bdb->bi_cache, e, rw );
+		bdb_unlocked_cache_return_entry_rw( &bdb->bi_cache, e, rw );
 	} else {
 		if (e->e_private != NULL)
 			free (e->e_private);
diff --git a/servers/slapd/back-bdb/modify.c b/servers/slapd/back-bdb/modify.c
index 184976e5e8..2e47ab49a5 100644
--- a/servers/slapd/back-bdb/modify.c
+++ b/servers/slapd/back-bdb/modify.c
@@ -249,6 +249,9 @@ bdb_modify(
 	DB_TXN	*ltid = NULL;
 	struct bdb_op_info opinfo;
 
+	u_int32_t	locker;
+	DB_LOCK		lock;
+
 #ifdef NEW_LOGGING
 	LDAP_LOG (( "modify", LDAP_LEVEL_ENTRY, "bdb_modify: %s\n", dn->bv_val ));
 #else
@@ -259,7 +262,7 @@ bdb_modify(
 retry:	/* transaction retry */
 		if( e != NULL ) {
 			bdb_cache_delete_entry(&bdb->bi_cache, e);
-			bdb_cache_return_entry_w(&bdb->bi_cache, e);
+			bdb_cache_return_entry_w(bdb->bi_dbenv, &bdb->bi_cache, e, &lock);
 		}
 #ifdef NEW_LOGGING
 		LDAP_LOG (( "modify", LDAP_LEVEL_DETAIL1, "bdb_modify: retrying...\n" ));
@@ -295,13 +298,15 @@ retry:	/* transaction retry */
 		goto return_results;
 	}
 
+	locker = TXN_ID ( ltid );
+
 	opinfo.boi_bdb = be;
 	opinfo.boi_txn = ltid;
 	opinfo.boi_err = 0;
 	op->o_private = &opinfo;
 
 	/* get entry */
-	rc = bdb_dn2entry_w( be, ltid, ndn, &e, &matched, 0 );
+	rc = bdb_dn2entry_w( be, ltid, ndn, &e, &matched, 0, locker, &lock );
 
 	if ( rc != 0 ) {
 #ifdef NEW_LOGGING
@@ -337,7 +342,7 @@ retry:	/* transaction retry */
 			refs = is_entry_referral( matched )
 				? get_entry_referrals( be, conn, op, matched )
 				: NULL;
-			bdb_cache_return_entry_r (&bdb->bi_cache, matched);
+			bdb_cache_return_entry_r (bdb->bi_dbenv, &bdb->bi_cache, matched, &lock);
 			matched = NULL;
 
 		} else {
@@ -463,7 +468,7 @@ done:
 	}
 
 	if( e != NULL ) {
-		bdb_cache_return_entry_w (&bdb->bi_cache, e);
+		bdb_cache_return_entry_w (bdb->bi_dbenv, &bdb->bi_cache, e, &lock);
 	}
 	return rc;
 }
diff --git a/servers/slapd/back-bdb/modrdn.c b/servers/slapd/back-bdb/modrdn.c
index cb1e1517eb..0a7e1de7ee 100644
--- a/servers/slapd/back-bdb/modrdn.c
+++ b/servers/slapd/back-bdb/modrdn.c
@@ -56,6 +56,9 @@ bdb_modrdn(
 
 	int		manageDSAit = get_manageDSAit( op );
 
+	u_int32_t	locker;
+	DB_LOCK		lock;
+
 #ifdef NEW_LOGGING
 	LDAP_LOG (( "modrdn", LDAP_LEVEL_ENTRY, "==>bdb_modrdn(%s,%s,%s)\n",
 		dn->bv_val,newrdn->bv_val,
@@ -78,13 +81,13 @@ bdb_modrdn(
 retry:	/* transaction retry */
 		if (e != NULL) {
 			bdb_cache_delete_entry(&bdb->bi_cache, e);
-			bdb_cache_return_entry_w(&bdb->bi_cache, e);
+			bdb_cache_return_entry_w(bdb->bi_dbenv, &bdb->bi_cache, e, &lock);
 		}
 		if (p != NULL) {
-			bdb_cache_return_entry_r(&bdb->bi_cache, p);
+			bdb_cache_return_entry_r(bdb->bi_dbenv, &bdb->bi_cache, p, &lock);
 		}
 		if (np != NULL) {
-			bdb_cache_return_entry_r(&bdb->bi_cache, np);
+			bdb_cache_return_entry_r(bdb->bi_dbenv, &bdb->bi_cache, np, &lock);
 		}
 #ifdef NEW_LOGGING
 		LDAP_LOG (( "modrdn", LDAP_LEVEL_DETAIL1, "==>bdb_modrdn: retrying...\n"));
@@ -119,13 +122,15 @@ retry:	/* transaction retry */
 		goto return_results;
 	}
 
+	locker = TXN_ID ( ltid );
+
 	opinfo.boi_bdb = be;
 	opinfo.boi_txn = ltid;
 	opinfo.boi_err = 0;
 	op->o_private = &opinfo;
 
 	/* get entry */
-	rc = bdb_dn2entry_w( be, ltid, ndn, &e, &matched, 0 );
+	rc = bdb_dn2entry_w( be, ltid, ndn, &e, &matched, 0, locker, &lock );
 
 	switch( rc ) {
 	case 0:
@@ -152,7 +157,7 @@ retry:	/* transaction retry */
 			refs = is_entry_referral( matched )
 				? get_entry_referrals( be, conn, op, matched )
 				: NULL;
-			bdb_cache_return_entry_r( &bdb->bi_cache, matched );
+			bdb_cache_return_entry_r( bdb->bi_dbenv, &bdb->bi_cache, matched, &lock );
 			matched = NULL;
 
 		} else {
@@ -199,7 +204,7 @@ retry:	/* transaction retry */
 		/* Make sure parent entry exist and we can write its 
 		 * children.
 		 */
-		rc = bdb_dn2entry_r( be, ltid, &p_ndn, &p, NULL, 0 );
+		rc = bdb_dn2entry_r( be, ltid, &p_ndn, &p, NULL, 0, locker, &lock );
 
 		switch( rc ) {
 		case 0:
@@ -348,7 +353,7 @@ retry:	/* transaction retry */
 			/* newSuperior == entry being moved?, if so ==> ERROR */
 			/* Get Entry with dn=newSuperior. Does newSuperior exist? */
 
-			rc = bdb_dn2entry_r( be, ltid, nnewSuperior, &np, NULL, 0 );
+			rc = bdb_dn2entry_r( be, ltid, nnewSuperior, &np, NULL, 0, locker, &lock );
 
 			switch( rc ) {
 			case 0:
@@ -855,17 +860,17 @@ done:
 	/* LDAP v3 Support */
 	if( np != NULL ) {
 		/* free new parent and reader lock */
-		bdb_cache_return_entry_r(&bdb->bi_cache, np);
+		bdb_cache_return_entry_r(bdb->bi_dbenv, &bdb->bi_cache, np, &lock);
 	}
 
 	if( p != NULL ) {
 		/* free parent and reader lock */
-		bdb_cache_return_entry_r(&bdb->bi_cache, p);
+		bdb_cache_return_entry_r(bdb->bi_dbenv, &bdb->bi_cache, p, &lock);
 	}
 
 	/* free entry */
 	if( e != NULL ) {
-		bdb_cache_return_entry_w( &bdb->bi_cache, e );
+		bdb_cache_return_entry_w( bdb->bi_dbenv, &bdb->bi_cache, e, &lock );
 	}
 
 	if( ltid != NULL ) {
diff --git a/servers/slapd/back-bdb/operational.c b/servers/slapd/back-bdb/operational.c
index 08172b8c2d..d0517abf9e 100644
--- a/servers/slapd/back-bdb/operational.c
+++ b/servers/slapd/back-bdb/operational.c
@@ -44,9 +44,11 @@ bdb_operational(
 
 	if( 0 ) {
 retry:	/* transaction retry */
+#if 0
 		if( e != NULL ) {
-			bdb_cache_return_entry_w(&bdb->bi_cache, e);
+			bdb_cache_return_entry_w(bdb->bi_dbenv, &bdb->bi_cache, e, &lock);
 		}
+#endif
 #ifdef NEW_LOGGING
 		LDAP_LOG (( "operational", LDAP_LEVEL_DETAIL1,
 			"=> bdb_operational: retrying...\n" ));
diff --git a/servers/slapd/back-bdb/passwd.c b/servers/slapd/back-bdb/passwd.c
index 0e05443926..25f0c654ed 100644
--- a/servers/slapd/back-bdb/passwd.c
+++ b/servers/slapd/back-bdb/passwd.c
@@ -41,6 +41,9 @@ bdb_exop_passwd(
 	struct berval dn;
 	struct berval ndn;
 
+	u_int32_t	locker;
+	DB_LOCK		lock;
+
 	assert( reqoid != NULL );
 	assert( strcmp( LDAP_EXOP_MODIFY_PASSWD, reqoid ) == 0 );
 
@@ -109,7 +112,7 @@ bdb_exop_passwd(
 retry:	/* transaction retry */
 		if ( e != NULL ) {
 			bdb_cache_delete_entry(&bdb->bi_cache, e);
-			bdb_cache_return_entry_w(&bdb->bi_cache, e);
+			bdb_cache_return_entry_w(bdb->bi_dbenv, &bdb->bi_cache, e, &lock);
 		}
 #ifdef NEW_LOGGING
 		LDAP_LOG (( "passwd", LDAP_LEVEL_DETAIL1, "bdb_exop_passwd: retrying...\n" ));
@@ -144,13 +147,15 @@ retry:	/* transaction retry */
 		goto done;
 	}
 
+	locker = TXN_ID ( ltid );
+
 	opinfo.boi_bdb = be;
 	opinfo.boi_txn = ltid;
 	opinfo.boi_err = 0;
 	op->o_private = &opinfo;
 
 	/* get entry */
-	rc = bdb_dn2entry_w( be, ltid, &ndn, &e, NULL, 0 );
+	rc = bdb_dn2entry_w( be, ltid, &ndn, &e, NULL, 0 , locker, &lock);
 
 	switch(rc) {
 	case DB_LOCK_DEADLOCK:
@@ -256,7 +261,7 @@ retry:	/* transaction retry */
 
 done:
 	if( e != NULL ) {
-		bdb_cache_return_entry_w( &bdb->bi_cache, e );
+		bdb_cache_return_entry_w( bdb->bi_dbenv, &bdb->bi_cache, e, &lock );
 	}
 		
 	if( hash.bv_val != NULL ) {
diff --git a/servers/slapd/back-bdb/proto-bdb.h b/servers/slapd/back-bdb/proto-bdb.h
index cdea9803e1..7cfe90293f 100644
--- a/servers/slapd/back-bdb/proto-bdb.h
+++ b/servers/slapd/back-bdb/proto-bdb.h
@@ -58,9 +58,9 @@ bdb_db_cache(
  * dn2entry.c
  */
 int bdb_dn2entry_rw LDAP_P(( BackendDB *be, DB_TXN *tid,
-       struct berval *dn, Entry **e, Entry **matched, int flags, int rw ));
-#define bdb_dn2entry_r(be, tid, dn, e, m, f) bdb_dn2entry_rw((be), (tid), (dn), (e), (m), (f), 0)
-#define bdb_dn2entry_w(be, tid, dn, e, m, f) bdb_dn2entry_rw((be), (tid), (dn), (e), (m), (f), 1)
+       struct berval *dn, Entry **e, Entry **matched, int flags, int rw , u_int32_t locker, DB_LOCK *lock));
+#define bdb_dn2entry_r(be, tid, dn, e, m, f, locker, lock) bdb_dn2entry_rw((be), (tid), (dn), (e), (m), (f), 0, locker, lock)
+#define bdb_dn2entry_w(be, tid, dn, e, m, f, locker, lock) bdb_dn2entry_rw((be), (tid), (dn), (e), (m), (f), 1, locker, lock)
 
 /*
  * dn2id.c
@@ -152,9 +152,11 @@ int bdb_id2entry_rw(
 	DB_TXN *tid,
 	ID id,
 	Entry **e,
-	int rw );
-#define bdb_id2entry_r(be, tid, id, e)      bdb_id2entry_rw((be), (tid), (id), (e), 0)
-#define bdb_id2entry_w(be, tid, id, e)      bdb_id2entry_rw((be), (tid), (id), (e), 1)
+	int rw,
+	u_int32_t locker,
+	DB_LOCK *lock );
+#define bdb_id2entry_r(be, tid, id, e, locker, lock)      bdb_id2entry_rw((be), (tid), (id), (e), 0, locker, lock)
+#define bdb_id2entry_w(be, tid, id, e, locker, lock)      bdb_id2entry_rw((be), (tid), (id), (e), 1, locker, lock)
 
 void bdb_entry_free ( Entry *e );
 
@@ -301,13 +303,19 @@ BI_op_extended bdb_exop_passwd;
  */
 
 void bdb_cache_entry_commit( Entry *e );
-void bdb_cache_return_entry_rw( Cache *cache, Entry *e, int rw );
-#define bdb_cache_return_entry_r(c, e) bdb_cache_return_entry_rw((c), (e), 0)
-#define bdb_cache_return_entry_w(c, e) bdb_cache_return_entry_rw((c), (e), 1)
+void bdb_cache_return_entry_rw( DB_ENV *env, Cache *cache, Entry *e, int rw, DB_LOCK *lock );
+#define bdb_cache_return_entry_r(env, c, e, l) bdb_cache_return_entry_rw((env), (c), (e), 0, (l))
+#define bdb_cache_return_entry_w(env, c, e, l) bdb_cache_return_entry_rw((env), (c), (e), 1, (l))
+void bdb_unlocked_cache_return_entry_rw( Cache *cache, Entry *e, int rw );
+#define bdb_unlocked_cache_return_entry_r( c, e ) bdb_cache_return_entry_rw((c), (e), 0)
+#define bdb_unlocked_cache_return_entry_w( c, e ) bdb_cache_return_entry_rw((c), (e), 1)
 int bdb_cache_add_entry_rw(
-       Cache   *cache,
-       Entry   *e,
-       int     rw
+	DB_ENV	*env,
+	Cache   *cache,
+	Entry   *e,
+	int     rw,
+	u_int32_t locker,
+	DB_LOCK	*lock
 );
 int bdb_cache_update_entry(
        Cache   *cache,
@@ -319,9 +327,12 @@ ID bdb_cache_find_entry_ndn2id(
        struct berval   *ndn
 );
 Entry* bdb_cache_find_entry_id(
-       Cache   *cache,
-       ID      id,
-       int     rw
+	DB_ENV		*env,
+	Cache		*cache,
+	ID		id,
+	int		rw,
+	u_int32_t	locker,
+	DB_LOCK		*lock
 );
 int bdb_cache_delete_entry(
        Cache   *cache,
diff --git a/servers/slapd/back-bdb/referral.c b/servers/slapd/back-bdb/referral.c
index 3517492c79..4d60f68d0e 100644
--- a/servers/slapd/back-bdb/referral.c
+++ b/servers/slapd/back-bdb/referral.c
@@ -26,6 +26,9 @@ bdb_referrals(
 	Entry *e = NULL;
 	Entry *matched = NULL;
 
+	u_int32_t	locker;
+	DB_LOCK		lock;
+
 	if( op->o_tag == LDAP_REQ_SEARCH ) {
 		/* let search take care of itself */
 		return rc;
@@ -36,8 +39,11 @@ bdb_referrals(
 		return rc;
 	} 
 
+	LOCK_ID ( bdb->bi_dbenv, &locker );
+
+dn2entry_retry:
 	/* get entry */
-	rc = bdb_dn2entry_r( be, NULL, ndn, &e, &matched, 0 );
+	rc = bdb_dn2entry_r( be, NULL, ndn, &e, &matched, 0, locker, &lock );
 
 	switch(rc) {
 	case DB_NOTFOUND:
@@ -46,14 +52,18 @@ bdb_referrals(
 		break;
 	case LDAP_BUSY:
 		if (e != NULL) {
-			bdb_cache_return_entry_r(&bdb->bi_cache, e);
+			bdb_cache_return_entry_r(bdb->bi_dbenv, &bdb->bi_cache, e, &lock);
 		}
 		if (matched != NULL) {
-			bdb_cache_return_entry_r(&bdb->bi_cache, matched);
+			bdb_cache_return_entry_r(bdb->bi_dbenv, &bdb->bi_cache, matched, &lock);
 		}
 		send_ldap_result( conn, op, LDAP_BUSY,
 			NULL, "ldap server busy", NULL, NULL );
+		LOCK_ID_FREE ( bdb->bi_dbenv, locker );
 		return LDAP_BUSY;
+	case DB_LOCK_DEADLOCK:
+	case DB_LOCK_NOTGRANTED:
+		goto dn2entry_retry;
 	default:
 #ifdef NEW_LOGGING
 		LDAP_LOG (( "referral", LDAP_LEVEL_ERR,
@@ -65,13 +75,14 @@ bdb_referrals(
 			db_strerror(rc), rc, 0 ); 
 #endif
 		if (e != NULL) {
-                        bdb_cache_return_entry_r(&bdb->bi_cache, e);
+                        bdb_cache_return_entry_r(bdb->bi_dbenv, &bdb->bi_cache, e, &lock);
 		}
                 if (matched != NULL) {
-                        bdb_cache_return_entry_r(&bdb->bi_cache, matched);
+                        bdb_cache_return_entry_r(bdb->bi_dbenv, &bdb->bi_cache, matched, &lock);
 		}
 		send_ldap_result( conn, op, rc=LDAP_OTHER,
 			NULL, "internal error", NULL, NULL );
+		LOCK_ID_FREE ( bdb->bi_dbenv, locker );
 		return rc;
 	}
 
@@ -97,7 +108,7 @@ bdb_referrals(
 				refs = get_entry_referrals( be, conn, op, matched );
 			}
 
-			bdb_cache_return_entry_r (&bdb->bi_cache, matched);
+			bdb_cache_return_entry_r (bdb->bi_dbenv, &bdb->bi_cache, matched, &lock);
 			matched = NULL;
 		} else if ( default_referral != NULL ) {
 			rc = LDAP_OTHER;
@@ -116,6 +127,7 @@ bdb_referrals(
 				NULL, NULL );
 		}
 
+		LOCK_ID_FREE ( bdb->bi_dbenv, locker );
 		free( matched_dn );
 		return rc;
 	}
@@ -148,6 +160,7 @@ bdb_referrals(
 		ber_bvarray_free( refs );
 	}
 
-	bdb_cache_return_entry_r(&bdb->bi_cache, e);
+	bdb_cache_return_entry_r(bdb->bi_dbenv, &bdb->bi_cache, e, &lock);
+	LOCK_ID_FREE ( bdb->bi_dbenv, locker );
 	return rc;
 }
diff --git a/servers/slapd/back-bdb/search.c b/servers/slapd/back-bdb/search.c
index 9887feb342..5dabe6b49f 100644
--- a/servers/slapd/back-bdb/search.c
+++ b/servers/slapd/back-bdb/search.c
@@ -59,6 +59,9 @@ bdb_search(
 	struct slap_limits_set *limit = NULL;
 	int isroot = 0;
 
+	u_int32_t	locker;
+	DB_LOCK		lock;
+
 #ifdef NEW_LOGGING
 	LDAP_LOG (( "search", LDAP_LEVEL_ENTRY,"bdb_back_search\n"));
 #else
@@ -68,6 +71,8 @@ bdb_search(
 
 	manageDSAit = get_manageDSAit( op );
 
+	LOCK_ID (bdb->bi_dbenv, &locker );
+
 	if ( nbase->bv_len == 0 ) {
 		/* DIT root special case */
 		e = (Entry *) &slap_entry_root;
@@ -81,7 +86,8 @@ bdb_search(
 	} else
 #endif
 	{
-		rc = bdb_dn2entry_r( be, NULL, nbase, &e, &matched, 0 );
+dn2entry_retry:
+		rc = bdb_dn2entry_r( be, NULL, nbase, &e, &matched, 0, locker, &lock );
 	}
 
 	switch(rc) {
@@ -90,23 +96,28 @@ bdb_search(
 		break;
 	case LDAP_BUSY:
 		if (e != NULL) {
-			bdb_cache_return_entry_r(&bdb->bi_cache, e);
+			bdb_cache_return_entry_r(bdb->bi_dbenv, &bdb->bi_cache, e, &lock);
 		}
 		if (matched != NULL) {
-			bdb_cache_return_entry_r(&bdb->bi_cache, matched);
+			bdb_cache_return_entry_r(bdb->bi_dbenv, &bdb->bi_cache, matched, &lock);
 		}
 		send_ldap_result( conn, op, LDAP_BUSY,
 			NULL, "ldap server busy", NULL, NULL );
+		LOCK_ID_FREE (bdb->bi_dbenv, locker );
 		return LDAP_BUSY;
+	case DB_LOCK_DEADLOCK:
+	case DB_LOCK_NOTGRANTED:
+		goto dn2entry_retry;
 	default:
 		if (e != NULL) {
-			bdb_cache_return_entry_r(&bdb->bi_cache, e);
+			bdb_cache_return_entry_r(bdb->bi_dbenv, &bdb->bi_cache, e, &lock);
 		}
 		if (matched != NULL) {
-			bdb_cache_return_entry_r(&bdb->bi_cache, matched);
+			bdb_cache_return_entry_r(bdb->bi_dbenv, &bdb->bi_cache, matched, &lock);
 		}
 		send_ldap_result( conn, op, rc=LDAP_OTHER,
 			NULL, "internal error", NULL, NULL );
+		LOCK_ID_FREE (bdb->bi_dbenv, locker );
 		return rc;
 	}
 
@@ -123,7 +134,7 @@ bdb_search(
 				? get_entry_referrals( be, conn, op, matched )
 				: NULL;
 
-			bdb_cache_return_entry_r (&bdb->bi_cache, matched);
+			bdb_cache_return_entry_r (bdb->bi_dbenv, &bdb->bi_cache, matched, &lock);
 			matched = NULL;
 
 			if( erefs ) {
@@ -140,6 +151,7 @@ bdb_search(
 		send_ldap_result( conn, op,	rc=LDAP_REFERRAL ,
 			matched_dn.bv_val, text, refs, NULL );
 
+		LOCK_ID_FREE (bdb->bi_dbenv, locker );
 		if ( refs ) ber_bvarray_free( refs );
 		if ( matched_dn.bv_val ) ber_memfree( matched_dn.bv_val );
 		return rc;
@@ -154,7 +166,7 @@ bdb_search(
 		erefs = get_entry_referrals( be, conn, op, e );
 		refs = NULL;
 
-		bdb_cache_return_entry_r( &bdb->bi_cache, e );
+		bdb_cache_return_entry_r( bdb->bi_dbenv, &bdb->bi_cache, e, &lock );
 		e = NULL;
 
 		if( erefs ) {
@@ -175,6 +187,7 @@ bdb_search(
 			refs ? NULL : "bad referral object",
 			refs, NULL );
 
+		LOCK_ID_FREE (bdb->bi_dbenv, locker );
 		ber_bvarray_free( refs );
 		ber_memfree( matched_dn.bv_val );
 		return 1;
@@ -270,7 +283,7 @@ bdb_search(
 	cursor = e->e_id == NOID ? 1 : e->e_id;
 
 	if ( e != &slap_entry_root ) {
-		bdb_cache_return_entry_r(&bdb->bi_cache, e);
+		bdb_cache_return_entry_r(bdb->bi_dbenv, &bdb->bi_cache, e, &lock);
 	}
 	e = NULL;
 
@@ -320,14 +333,18 @@ bdb_search(
 			goto done;
 		}
 
+id2entry_retry:
 		/* get the entry with reader lock */
-		rc = bdb_id2entry_r( be, NULL, id, &e );
+		rc = bdb_id2entry_r( be, NULL, id, &e, locker, &lock );
 
 		if (rc == LDAP_BUSY) {
 			send_ldap_result( conn, op, rc=LDAP_BUSY,
 				NULL, "ldap server busy", NULL, NULL );
 			goto done;
 		}
+		else if ( rc == DB_LOCK_DEADLOCK || rc == DB_LOCK_NOTGRANTED ) {
+			goto id2entry_retry;	
+		}
 
 		if ( e == NULL ) {
 			if( !BDB_IDL_IS_RANGE(candidates) ) {
@@ -456,7 +473,7 @@ bdb_search(
 			if ( scopeok ) {
 				/* check size limit */
 				if ( --slimit == -1 ) {
-					bdb_cache_return_entry_r (&bdb->bi_cache, e);
+					bdb_cache_return_entry_r (bdb->bi_dbenv, &bdb->bi_cache, e, &lock);
 					e = NULL;
 					send_search_result( conn, op,
 						rc = LDAP_SIZELIMIT_EXCEEDED, NULL, NULL,
@@ -481,7 +498,7 @@ bdb_search(
 					case 1:		/* entry not sent */
 						break;
 					case -1:	/* connection closed */
-						bdb_cache_return_entry_r(&bdb->bi_cache, e);
+						bdb_cache_return_entry_r(bdb->bi_dbenv, &bdb->bi_cache, e, &lock);
 						e = NULL;
 						rc = LDAP_OTHER;
 						goto done;
@@ -509,7 +526,7 @@ bdb_search(
 loop_continue:
 		if( e != NULL ) {
 			/* free reader lock */
-                        bdb_cache_return_entry_r ( &bdb->bi_cache, e );
+                        bdb_cache_return_entry_r ( bdb->bi_dbenv, &bdb->bi_cache, e , &lock);
                         e = NULL;
 		}
 
@@ -524,9 +541,11 @@ loop_continue:
 done:
 	if( e != NULL ) {
 		/* free reader lock */
-		bdb_cache_return_entry_r ( &bdb->bi_cache, e );
+		bdb_cache_return_entry_r ( bdb->bi_dbenv, &bdb->bi_cache, e, &lock );
 	}
 
+	LOCK_ID_FREE (bdb->bi_dbenv, locker );
+
 	if( v2refs ) ber_bvarray_free( v2refs );
 	if( realbase.bv_val ) ch_free( realbase.bv_val );