From d7fa1e764db0aa3215414f5fbf2fec27416beef9 Mon Sep 17 00:00:00 2001
From: Howard Chu <hyc@openldap.org>
Date: Mon, 1 Jan 2007 01:00:19 +0000
Subject: [PATCH] partial revert - keep acquiring BDB lock in lru_purge.

---
 servers/slapd/back-bdb/back-bdb.h |  3 +-
 servers/slapd/back-bdb/cache.c    | 63 ++++++++++++++++++++-----------
 servers/slapd/back-bdb/init.c     | 10 +++++
 3 files changed, 52 insertions(+), 24 deletions(-)

diff --git a/servers/slapd/back-bdb/back-bdb.h b/servers/slapd/back-bdb/back-bdb.h
index ae25890a90..f25f247da1 100644
--- a/servers/slapd/back-bdb/back-bdb.h
+++ b/servers/slapd/back-bdb/back-bdb.h
@@ -127,9 +127,10 @@ typedef struct bdb_cache {
 	int		c_minfree;
 	int		c_eiused;	/* EntryInfo's in use */
 	int		c_leaves;	/* EntryInfo leaf nodes */
+	u_int32_t	c_locker;	/* used by lru cleaner */
 	EntryInfo	c_dntree;
 	EntryInfo	*c_eifree;	/* free list */
-	Avlnode         *c_idtree;
+	Avlnode		*c_idtree;
 	EntryInfo	*c_lruhead;	/* lru - add accessed entries here */
 	EntryInfo	*c_lrutail;	/* lru - rem lru entries from here */
 	ldap_pvt_thread_rdwr_t c_rwlock;
diff --git a/servers/slapd/back-bdb/cache.c b/servers/slapd/back-bdb/cache.c
index 160de89ae1..77b816b1e8 100644
--- a/servers/slapd/back-bdb/cache.c
+++ b/servers/slapd/back-bdb/cache.c
@@ -556,6 +556,7 @@ int hdb_cache_load(
 static void
 bdb_cache_lru_purge( struct bdb_info *bdb )
 {
+	DB_LOCK		lock, *lockp;
 	EntryInfo *elru, *elnext;
 	int count, islocked;
 
@@ -568,6 +569,12 @@ bdb_cache_lru_purge( struct bdb_info *bdb )
 		return;
 	}
 
+	if ( bdb->bi_cache.c_locker ) {
+		lockp = &lock;
+	} else {
+		lockp = NULL;
+	}
+
 	count = 0;
 	/* Look for an unused entry to remove */
 	for (elru = bdb->bi_cache.c_lruhead; elru; elru = elnext ) {
@@ -592,33 +599,43 @@ bdb_cache_lru_purge( struct bdb_info *bdb )
 			continue;
 		}
 
+		/* entryinfo is locked */
 		islocked = 1;
 
-		/* Free entry for this node if it's present */
-		if ( elru->bei_e ) {
-			elru->bei_e->e_private = NULL;
-#ifdef SLAP_ZONE_ALLOC
-			bdb_entry_return( bdb, elru->bei_e, elru->bei_zseq );
-#else
-			bdb_entry_return( elru->bei_e );
-#endif
-			elru->bei_e = NULL;
-			count++;
-		}
-		/* ITS#4010 if we're in slapcat, and this node is a leaf
-		 * node, free it.
-		 *
-		 * FIXME: we need to do this for slapd as well, (which is
-		 * why we compute bi_cache.c_leaves now) but at the moment
-		 * we can't because it causes unresolvable deadlocks. 
+		/* If we can successfully writelock it, then
+		 * the object is idle.
 		 */
-		if ( slapMode & SLAP_TOOL_READONLY ) {
-			if ( !elru->bei_kids ) {
-				bdb_cache_delete_internal( &bdb->bi_cache, elru, 0 );
-				bdb_cache_delete_cleanup( &bdb->bi_cache, elru );
-				islocked = 0;
+		if ( bdb_cache_entry_db_lock( bdb->bi_dbenv,
+			bdb->bi_cache.c_locker, elru, 1, 1, lockp ) == 0 ) {
+
+			/* Free entry for this node if it's present */
+			if ( elru->bei_e ) {
+				elru->bei_e->e_private = NULL;
+#ifdef SLAP_ZONE_ALLOC
+				bdb_entry_return( bdb, elru->bei_e, elru->bei_zseq );
+#else
+				bdb_entry_return( elru->bei_e );
+#endif
+				elru->bei_e = NULL;
+				count++;
+			}
+			bdb_cache_entry_dbunlock( bdb, lockp );
+
+			/* ITS#4010 if we're in slapcat, and this node is a leaf
+			 * node, free it.
+			 *
+			 * FIXME: we need to do this for slapd as well, (which is
+			 * why we compute bi_cache.c_leaves now) but at the moment
+			 * we can't because it causes unresolvable deadlocks. 
+			 */
+			if ( slapMode & SLAP_TOOL_READONLY ) {
+				if ( !elru->bei_kids ) {
+					bdb_cache_delete_internal( &bdb->bi_cache, elru, 0 );
+					bdb_cache_delete_cleanup( &bdb->bi_cache, elru );
+					islocked = 0;
+				}
+				/* Leave node on LRU list for a future pass */
 			}
-			/* Leave node on LRU list for a future pass */
 		}
 
 		if ( islocked )
diff --git a/servers/slapd/back-bdb/init.c b/servers/slapd/back-bdb/init.c
index 194c833cff..624f157e77 100644
--- a/servers/slapd/back-bdb/init.c
+++ b/servers/slapd/back-bdb/init.c
@@ -423,6 +423,10 @@ bdb_db_open( BackendDB *be )
 		goto fail;
 	}
 
+	if ( !quick ) {
+		XLOCK_ID(bdb->bi_dbenv, &bdb->bi_cache.c_locker);
+	}
+
 	/* monitor setup */
 	rc = bdb_monitor_db_open( be );
 	if ( rc != 0 ) {
@@ -486,6 +490,12 @@ bdb_db_close( BackendDB *be )
 
 	/* close db environment */
 	if( bdb->bi_dbenv ) {
+		/* Free cache locker if we enabled locking */
+		if ( !( slapMode & SLAP_TOOL_QUICK )) {
+			XLOCK_ID_FREE(bdb->bi_dbenv, bdb->bi_cache.c_locker);
+			bdb->bi_cache.c_locker = 0;
+		}
+
 		/* force a checkpoint, but not if we were ReadOnly,
 		 * and not in Quick mode since there are no transactions there.
 		 */