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cache.c

/* cache.c - routines to maintain an in-core cache of entries */
/* $OpenLDAP: pkg/ldap/servers/slapd/back-bdb/cache.c,v 1.120.2.15 2008/05/01 21:39:35 quanah Exp $ */
/* This work is part of OpenLDAP Software <http://www.openldap.org/>.
 *
 * Copyright 2000-2008 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 the file LICENSE in the
 * top-level directory of the distribution or, alternatively, at
 * <http://www.OpenLDAP.org/license.html>.
 */

#include "portable.h"

#include <stdio.h>

#include <ac/errno.h>
#include <ac/string.h>
#include <ac/socket.h>

#include "slap.h"

#include "back-bdb.h"

#include "ldap_rq.h"

#ifdef BDB_HIER
#define bdb_cache_lru_purge   hdb_cache_lru_purge
#endif
static void bdb_cache_lru_purge( struct bdb_info *bdb );

static int  bdb_cache_delete_internal(Cache *cache, EntryInfo *e, int decr);
#ifdef LDAP_DEBUG
#define SLAPD_UNUSED
#ifdef SLAPD_UNUSED
static void bdb_lru_print(Cache *cache);
#endif
#endif

/* For concurrency experiments only! */
#if 0
#define     ldap_pvt_thread_rdwr_wlock(a) 0
#define     ldap_pvt_thread_rdwr_wunlock(a)     0
#define     ldap_pvt_thread_rdwr_rlock(a) 0
#define     ldap_pvt_thread_rdwr_runlock(a)     0
#endif

#if 0
#define ldap_pvt_thread_mutex_trylock(a) 0
#endif

static EntryInfo *
bdb_cache_entryinfo_new( Cache *cache )
{
      EntryInfo *ei = NULL;

      if ( cache->c_eifree ) {
            ldap_pvt_thread_mutex_lock( &cache->c_eifree_mutex );
            if ( cache->c_eifree ) {
                  ei = cache->c_eifree;
                  cache->c_eifree = ei->bei_lrunext;
                  ei->bei_finders = 0;
            }
            ldap_pvt_thread_mutex_unlock( &cache->c_eifree_mutex );
      }
      if ( !ei ) {
            ei = ch_calloc(1, sizeof(EntryInfo));
            ldap_pvt_thread_mutex_init( &ei->bei_kids_mutex );
      }

      ei->bei_state = CACHE_ENTRY_REFERENCED;

      return ei;
}

static void
bdb_cache_entryinfo_free( Cache *cache, EntryInfo *ei )
{
      free( ei->bei_nrdn.bv_val );
      ei->bei_nrdn.bv_val = NULL;
#ifdef BDB_HIER
      free( ei->bei_rdn.bv_val );
      ei->bei_rdn.bv_val = NULL;
      ei->bei_modrdns = 0;
      ei->bei_ckids = 0;
      ei->bei_dkids = 0;
#endif
      ei->bei_parent = NULL;
      ei->bei_kids = NULL;
      ei->bei_lruprev = NULL;

      ldap_pvt_thread_mutex_lock( &cache->c_eifree_mutex );
      ei->bei_lrunext = cache->c_eifree;
      cache->c_eifree = ei;
      ldap_pvt_thread_mutex_unlock( &cache->c_eifree_mutex );
}

#define LRU_DEL( c, e ) do { \
      if ( e == (c)->c_lruhead ) (c)->c_lruhead = e->bei_lruprev; \
      if ( e == (c)->c_lrutail ) (c)->c_lrutail = e->bei_lruprev; \
      e->bei_lrunext->bei_lruprev = e->bei_lruprev; \
      e->bei_lruprev->bei_lrunext = e->bei_lrunext; \
      e->bei_lruprev = NULL; \
} while ( 0 )

/* Note - we now use a Second-Chance / Clock algorithm instead of
 * Least-Recently-Used. This tremendously improves concurrency
 * because we no longer need to manipulate the lists every time an
 * entry is touched. We only need to lock the lists when adding
 * or deleting an entry. It's now a circular doubly-linked list.
 * We always append to the tail, but the head traverses the circle
 * during a purge operation.
 */
static void
bdb_cache_lru_link( struct bdb_info *bdb, EntryInfo *ei )
{

      /* Already linked, ignore */
      if ( ei->bei_lruprev )
            return;

      /* Insert into circular LRU list */
      ldap_pvt_thread_mutex_lock( &bdb->bi_cache.c_lru_mutex );

      ei->bei_lruprev = bdb->bi_cache.c_lrutail;
      if ( bdb->bi_cache.c_lrutail ) {
            ei->bei_lrunext = bdb->bi_cache.c_lrutail->bei_lrunext;
            bdb->bi_cache.c_lrutail->bei_lrunext = ei;
            if ( ei->bei_lrunext )
                  ei->bei_lrunext->bei_lruprev = ei;
      } else {
            ei->bei_lrunext = ei->bei_lruprev = ei;
            bdb->bi_cache.c_lruhead = ei;
      }
      bdb->bi_cache.c_lrutail = ei;
      ldap_pvt_thread_mutex_unlock( &bdb->bi_cache.c_lru_mutex );
}

#ifdef NO_THREADS
#define NO_DB_LOCK
#endif

/* #define NO_DB_LOCK 1 */
/* Note: The BerkeleyDB locks are much slower than regular
 * mutexes or rdwr locks. But the BDB implementation has the
 * advantage of using a fixed size lock table, instead of
 * allocating a lock object per entry in the DB. That's a
 * key benefit for scaling. It also frees us from worrying
 * about undetectable deadlocks between BDB activity and our
 * own cache activity. It's still worth exploring faster
 * alternatives though.
 */

/* Atomically release and reacquire a lock */
int
bdb_cache_entry_db_relock(
      struct bdb_info *bdb,
      BDB_LOCKER locker,
      EntryInfo *ei,
      int rw,
      int tryOnly,
      DB_LOCK *lock )
{
#ifdef NO_DB_LOCK
      return 0;
#else
      int   rc;
      DBT   lockobj;
      DB_LOCKREQ list[2];

      if ( !lock ) return 0;

      lockobj.data = &ei->bei_id;
      lockobj.size = sizeof(ei->bei_id) + 1;

      list[0].op = DB_LOCK_PUT;
      list[0].lock = *lock;
      list[1].op = DB_LOCK_GET;
      list[1].lock = *lock;
      list[1].mode = rw ? DB_LOCK_WRITE : DB_LOCK_READ;
      list[1].obj = &lockobj;
      rc = bdb->bi_dbenv->lock_vec(bdb->bi_dbenv, BDB_LOCKID(locker), tryOnly ? DB_LOCK_NOWAIT : 0,
            list, 2, NULL );

      if (rc && !tryOnly) {
            Debug( LDAP_DEBUG_TRACE,
                  "bdb_cache_entry_db_relock: entry %ld, rw %d, rc %d\n",
                  ei->bei_id, rw, rc );
      } else {
            *lock = list[1].lock;
      }
      return rc;
#endif
}

static int
bdb_cache_entry_db_lock( struct bdb_info *bdb, BDB_LOCKER locker, EntryInfo *ei,
      int rw, int tryOnly, DB_LOCK *lock )
{
#ifdef NO_DB_LOCK
      return 0;
#else
      int       rc;
      DBT       lockobj;
      int       db_rw;

      if ( !lock ) return 0;

      if (rw)
            db_rw = DB_LOCK_WRITE;
      else
            db_rw = DB_LOCK_READ;

      lockobj.data = &ei->bei_id;
      lockobj.size = sizeof(ei->bei_id) + 1;

      rc = LOCK_GET(bdb->bi_dbenv, BDB_LOCKID(locker), tryOnly ? DB_LOCK_NOWAIT : 0,
                              &lockobj, db_rw, lock);
      if (rc && !tryOnly) {
            Debug( LDAP_DEBUG_TRACE,
                  "bdb_cache_entry_db_lock: entry %ld, rw %d, rc %d\n",
                  ei->bei_id, rw, rc );
      }
      return rc;
#endif /* NO_DB_LOCK */
}

int
bdb_cache_entry_db_unlock ( struct bdb_info *bdb, DB_LOCK *lock )
{
#ifdef NO_DB_LOCK
      return 0;
#else
      int rc;

      if ( !lock || lock->mode == DB_LOCK_NG ) return 0;

      rc = LOCK_PUT ( bdb->bi_dbenv, lock );
      return rc;
#endif
}

void
bdb_cache_return_entry_rw( struct bdb_info *bdb, Entry *e,
      int rw, DB_LOCK *lock )
{
      EntryInfo *ei;
      int free = 0;

      ei = e->e_private;
      if ( ei &&
            ( ei->bei_state & CACHE_ENTRY_NOT_CACHED ) &&
            ( bdb_cache_entryinfo_trylock( ei ) == 0 )) {
            if ( ei->bei_state & CACHE_ENTRY_NOT_CACHED ) {
                  /* Releasing the entry can only be done when
                   * we know that nobody else is using it, i.e we
                   * should have an entry_db writelock.  But the
                   * flag is only set by the thread that loads the
                   * entry, and only if no other threads has found
                   * it while it was working.  All other threads
                   * clear the flag, which mean that we should be
                   * the only thread using the entry if the flag
                   * is set here.
                   */
                  ei->bei_e = NULL;
                  ei->bei_state ^= CACHE_ENTRY_NOT_CACHED;
                  free = 1;
            }
            bdb_cache_entryinfo_unlock( ei );
      }
      bdb_cache_entry_db_unlock( bdb, lock );
      if ( free ) {
            e->e_private = NULL;
            bdb_entry_return( e );
      }
}

static int
bdb_cache_entryinfo_destroy( EntryInfo *e )
{
      ldap_pvt_thread_mutex_destroy( &e->bei_kids_mutex );
      free( e->bei_nrdn.bv_val );
#ifdef BDB_HIER
      free( e->bei_rdn.bv_val );
#endif
      free( e );
      return 0;
}

/* Do a length-ordered sort on normalized RDNs */
static int
bdb_rdn_cmp( const void *v_e1, const void *v_e2 )
{
      const EntryInfo *e1 = v_e1, *e2 = v_e2;
      int rc = e1->bei_nrdn.bv_len - e2->bei_nrdn.bv_len;
      if (rc == 0) {
            rc = strncmp( e1->bei_nrdn.bv_val, e2->bei_nrdn.bv_val,
                  e1->bei_nrdn.bv_len );
      }
      return rc;
}

static int
bdb_id_cmp( const void *v_e1, const void *v_e2 )
{
      const EntryInfo *e1 = v_e1, *e2 = v_e2;
      return e1->bei_id - e2->bei_id;
}

static int
bdb_id_dup_err( void *v1, void *v2 )
{
      EntryInfo *e2 = v2;
      e2->bei_lrunext = v1;
      return -1;
}

/* Create an entryinfo in the cache. Caller must release the locks later.
 */
static int
bdb_entryinfo_add_internal(
      struct bdb_info *bdb,
      EntryInfo *ei,
      EntryInfo **res )
{
      EntryInfo *ei2 = NULL;

      *res = NULL;

      ei2 = bdb_cache_entryinfo_new( &bdb->bi_cache );

      ldap_pvt_thread_rdwr_wlock( &bdb->bi_cache.c_rwlock );
      bdb_cache_entryinfo_lock( ei->bei_parent );

      ei2->bei_id = ei->bei_id;
      ei2->bei_parent = ei->bei_parent;
#ifdef BDB_HIER
      ei2->bei_rdn = ei->bei_rdn;
#endif
#ifdef SLAP_ZONE_ALLOC
      ei2->bei_bdb = bdb;
#endif

      /* Add to cache ID tree */
      if (avl_insert( &bdb->bi_cache.c_idtree, ei2, bdb_id_cmp,
            bdb_id_dup_err )) {
            EntryInfo *eix = ei2->bei_lrunext;
            bdb_cache_entryinfo_free( &bdb->bi_cache, ei2 );
            ei2 = eix;
#ifdef BDB_HIER
            /* It got freed above because its value was
             * assigned to ei2.
             */
            ei->bei_rdn.bv_val = NULL;
#endif
      } else {
            int rc;

            bdb->bi_cache.c_eiused++;
            ber_dupbv( &ei2->bei_nrdn, &ei->bei_nrdn );

            /* This is a new leaf node. But if parent had no kids, then it was
             * a leaf and we would be decrementing that. So, only increment if
             * the parent already has kids.
             */
            if ( ei->bei_parent->bei_kids || !ei->bei_parent->bei_id )
                  bdb->bi_cache.c_leaves++;
            rc = avl_insert( &ei->bei_parent->bei_kids, ei2, bdb_rdn_cmp,
                  avl_dup_error );
            if ( rc ) {
                  /* This should never happen; entry cache is corrupt */
                  bdb->bi_dbenv->log_flush( bdb->bi_dbenv, NULL );
                  assert( !rc );
            }
#ifdef BDB_HIER
            ei->bei_parent->bei_ckids++;
#endif
      }

      *res = ei2;
      return 0;
}

/* Find the EntryInfo for the requested DN. If the DN cannot be found, return
 * the info for its closest ancestor. *res should be NULL to process a
 * complete DN starting from the tree root. Otherwise *res must be the
 * immediate parent of the requested DN, and only the RDN will be searched.
 * The EntryInfo is locked upon return and must be unlocked by the caller.
 */
int
bdb_cache_find_ndn(
      Operation   *op,
      BDB_LOCKER        locker,
      struct berval     *ndn,
      EntryInfo   **res )
{
      struct bdb_info *bdb = (struct bdb_info *) op->o_bd->be_private;
      EntryInfo   ei, *eip, *ei2;
      int rc = 0;
      char *ptr;

      /* this function is always called with normalized DN */
      if ( *res ) {
            /* we're doing a onelevel search for an RDN */
            ei.bei_nrdn.bv_val = ndn->bv_val;
            ei.bei_nrdn.bv_len = dn_rdnlen( op->o_bd, ndn );
            eip = *res;
      } else {
            /* we're searching a full DN from the root */
            ptr = ndn->bv_val + ndn->bv_len - op->o_bd->be_nsuffix[0].bv_len;
            ei.bei_nrdn.bv_val = ptr;
            ei.bei_nrdn.bv_len = op->o_bd->be_nsuffix[0].bv_len;
            /* Skip to next rdn if suffix is empty */
            if ( ei.bei_nrdn.bv_len == 0 ) {
                  for (ptr = ei.bei_nrdn.bv_val - 2; ptr > ndn->bv_val
                        && !DN_SEPARATOR(*ptr); ptr--) /* empty */;
                  if ( ptr >= ndn->bv_val ) {
                        if (DN_SEPARATOR(*ptr)) ptr++;
                        ei.bei_nrdn.bv_len = ei.bei_nrdn.bv_val - ptr;
                        ei.bei_nrdn.bv_val = ptr;
                  }
            }
            eip = &bdb->bi_cache.c_dntree;
      }
      
      for ( bdb_cache_entryinfo_lock( eip ); eip; ) {
            eip->bei_state |= CACHE_ENTRY_REFERENCED;
            ei.bei_parent = eip;
            ei2 = (EntryInfo *)avl_find( eip->bei_kids, &ei, bdb_rdn_cmp );
            if ( !ei2 ) {
                  DB_LOCK lock;
                  int len = ei.bei_nrdn.bv_len;
                        
                  if ( BER_BVISEMPTY( ndn )) {
                        *res = eip;
                        return LDAP_SUCCESS;
                  }

                  ei.bei_nrdn.bv_len = ndn->bv_len -
                        (ei.bei_nrdn.bv_val - ndn->bv_val);
                  bdb_cache_entryinfo_unlock( eip );

                  BDB_LOG_PRINTF( bdb->bi_dbenv, NULL, "slapd Reading %s",
                        ei.bei_nrdn.bv_val );

                  lock.mode = DB_LOCK_NG;
                  rc = bdb_dn2id( op, &ei.bei_nrdn, &ei, locker, &lock );
                  if (rc) {
                        bdb_cache_entryinfo_lock( eip );
                        bdb_cache_entry_db_unlock( bdb, &lock );
                        *res = eip;
                        return rc;
                  }

                  BDB_LOG_PRINTF( bdb->bi_dbenv, NULL, "slapd Read got %s(%d)",
                        ei.bei_nrdn.bv_val, ei.bei_id );

                  /* DN exists but needs to be added to cache */
                  ei.bei_nrdn.bv_len = len;
                  rc = bdb_entryinfo_add_internal( bdb, &ei, &ei2 );
                  /* add_internal left eip and c_rwlock locked */
                  ldap_pvt_thread_rdwr_wunlock( &bdb->bi_cache.c_rwlock );
                  bdb_cache_entry_db_unlock( bdb, &lock );
                  if ( rc ) {
                        *res = eip;
                        return rc;
                  }
            } else if ( ei2->bei_state & CACHE_ENTRY_DELETED ) {
                  /* In the midst of deleting? Give it a chance to
                   * complete.
                   */
                  bdb_cache_entryinfo_unlock( eip );
                  ldap_pvt_thread_yield();
                  bdb_cache_entryinfo_lock( eip );
                  *res = eip;
                  return DB_NOTFOUND;
            }
            bdb_cache_entryinfo_unlock( eip );
            bdb_cache_entryinfo_lock( ei2 );

            eip = ei2;

            /* Advance to next lower RDN */
            for (ptr = ei.bei_nrdn.bv_val - 2; ptr > ndn->bv_val
                  && !DN_SEPARATOR(*ptr); ptr--) /* empty */;
            if ( ptr >= ndn->bv_val ) {
                  if (DN_SEPARATOR(*ptr)) ptr++;
                  ei.bei_nrdn.bv_len = ei.bei_nrdn.bv_val - ptr - 1;
                  ei.bei_nrdn.bv_val = ptr;
            }
            if ( ptr < ndn->bv_val ) {
                  *res = eip;
                  break;
            }
      }

      return rc;
}

#ifdef BDB_HIER
/* Walk up the tree from a child node, looking for an ID that's already
 * been linked into the cache.
 */
int
hdb_cache_find_parent(
      Operation *op,
      BDB_LOCKER  locker,
      ID id,
      EntryInfo **res )
{
      struct bdb_info *bdb = (struct bdb_info *) op->o_bd->be_private;
      EntryInfo ei, eip, *ei2 = NULL, *ein = NULL, *eir = NULL;
      int rc;

      ei.bei_id = id;
      ei.bei_kids = NULL;
      ei.bei_ckids = 0;

      for (;;) {
            rc = hdb_dn2id_parent( op, locker, &ei, &eip.bei_id );
            if ( rc ) break;

            /* Save the previous node, if any */
            ei2 = ein;

            /* Create a new node for the current ID */
            ein = bdb_cache_entryinfo_new( &bdb->bi_cache );
            ein->bei_id = ei.bei_id;
            ein->bei_kids = ei.bei_kids;
            ein->bei_nrdn = ei.bei_nrdn;
            ein->bei_rdn = ei.bei_rdn;
            ein->bei_ckids = ei.bei_ckids;
#ifdef SLAP_ZONE_ALLOC
            ein->bei_bdb = bdb;
#endif
            ei.bei_ckids = 0;
            
            /* This node is not fully connected yet */
            ein->bei_state |= CACHE_ENTRY_NOT_LINKED;

            /* Insert this node into the ID tree */
            ldap_pvt_thread_rdwr_wlock( &bdb->bi_cache.c_rwlock );
            if ( avl_insert( &bdb->bi_cache.c_idtree, (caddr_t)ein,
                  bdb_id_cmp, bdb_id_dup_err ) ) {
                  EntryInfo *eix = ein->bei_lrunext;

                  /* Someone else created this node just before us.
                   * Free our new copy and use the existing one.
                   */
                  bdb_cache_entryinfo_free( &bdb->bi_cache, ein );
                  ein = eix;
                  
                  /* Link in any kids we've already processed */
                  if ( ei2 ) {
                        bdb_cache_entryinfo_lock( ein );
                        avl_insert( &ein->bei_kids, (caddr_t)ei2,
                              bdb_rdn_cmp, avl_dup_error );
                        ein->bei_ckids++;
                        bdb_cache_entryinfo_unlock( ein );
                  }
            }

            /* If this is the first time, save this node
             * to be returned later.
             */
            if ( eir == NULL ) eir = ein;

            /* If there was a previous node, link it to this one */
            if ( ei2 ) ei2->bei_parent = ein;

            /* Look for this node's parent */
            if ( eip.bei_id ) {
                  ei2 = (EntryInfo *) avl_find( bdb->bi_cache.c_idtree,
                              (caddr_t) &eip, bdb_id_cmp );
            } else {
                  ei2 = &bdb->bi_cache.c_dntree;
            }
            bdb->bi_cache.c_eiused++;
            if ( ei2 && ( ei2->bei_kids || !ei2->bei_id ))
                        bdb->bi_cache.c_leaves++;
            ldap_pvt_thread_rdwr_wunlock( &bdb->bi_cache.c_rwlock );

            /* Got the parent, link in and we're done. */
            if ( ei2 ) {
                  bdb_cache_entryinfo_lock( eir );
                  bdb_cache_entryinfo_lock( ei2 );
                  ein->bei_parent = ei2;

                  avl_insert( &ei2->bei_kids, (caddr_t)ein, bdb_rdn_cmp,
                        avl_dup_error);
                  ei2->bei_ckids++;

                  /* Reset all the state info */
                  for (ein = eir; ein != ei2; ein=ein->bei_parent)
                        ein->bei_state &= ~CACHE_ENTRY_NOT_LINKED;

                  bdb_cache_entryinfo_unlock( ei2 );

                  *res = eir;
                  break;
            }
            ei.bei_kids = NULL;
            ei.bei_id = eip.bei_id;
            ei.bei_ckids = 1;
            avl_insert( &ei.bei_kids, (caddr_t)ein, bdb_rdn_cmp,
                  avl_dup_error );
      }
      return rc;
}

/* Used by hdb_dn2idl when loading the EntryInfo for all the children
 * of a given node
 */
int hdb_cache_load(
      struct bdb_info *bdb,
      EntryInfo *ei,
      EntryInfo **res )
{
      EntryInfo *ei2;
      int rc;

      /* See if we already have this one */
      bdb_cache_entryinfo_lock( ei->bei_parent );
      ei2 = (EntryInfo *)avl_find( ei->bei_parent->bei_kids, ei, bdb_rdn_cmp );
      bdb_cache_entryinfo_unlock( ei->bei_parent );

      if ( !ei2 ) {
            /* Not found, add it */
            struct berval bv;

            /* bei_rdn was not malloc'd before, do it now */
            ber_dupbv( &bv, &ei->bei_rdn );
            ei->bei_rdn = bv;

            rc = bdb_entryinfo_add_internal( bdb, ei, res );
            bdb_cache_entryinfo_unlock( ei->bei_parent );
            ldap_pvt_thread_rdwr_wunlock( &bdb->bi_cache.c_rwlock );
      } else {
            /* Found, return it */
            *res = ei2;
            return 0;
      }
      return rc;
}
#endif

/* This is best-effort only. If all entries in the cache are
 * busy, they will all be kept. This is unlikely to happen
 * unless the cache is very much smaller than the working set.
 */
static void
bdb_cache_lru_purge( struct bdb_info *bdb )
{
      DB_LOCK           lock, *lockp;
      EntryInfo *elru, *elnext = NULL;
      int count, islocked, eimax;

      /* Wait for the mutex; we're the only one trying to purge. */
      ldap_pvt_thread_mutex_lock( &bdb->bi_cache.c_lru_mutex );

      if ( bdb->bi_cache.c_cursize <= bdb->bi_cache.c_maxsize ) {
            ldap_pvt_thread_mutex_unlock( &bdb->bi_cache.c_lru_mutex );
            bdb->bi_cache.c_purging = 0;
            return;
      }

      if ( bdb->bi_cache.c_locker ) {
            lockp = &lock;
      } else {
            lockp = NULL;
      }

      count = 0;

      /* maximum number of EntryInfo leaves to cache. In slapcat
       * we always free all leaf nodes.
       */
      if ( slapMode & SLAP_TOOL_READONLY )
            eimax = 0;
      else
            eimax = bdb->bi_cache.c_eimax;

      /* Look for an unused entry to remove */
      for ( elru = bdb->bi_cache.c_lruhead; elru; elru = elnext ) {
            elnext = elru->bei_lrunext;

            if ( bdb_cache_entryinfo_trylock( elru ))
                  goto bottom;

            /* This flag implements the clock replacement behavior */
            if ( elru->bei_state & ( CACHE_ENTRY_REFERENCED )) {
                  elru->bei_state &= ~CACHE_ENTRY_REFERENCED;
                  bdb_cache_entryinfo_unlock( elru );
                  goto bottom;
            }

            /* If this node is in the process of linking into the cache,
             * or this node is being deleted, skip it.
             */
            if (( elru->bei_state & ( CACHE_ENTRY_NOT_LINKED |
                  CACHE_ENTRY_DELETED | CACHE_ENTRY_LOADING )) ||
                  elru->bei_finders > 0 ) {
                  bdb_cache_entryinfo_unlock( elru );
                  goto bottom;
            }

            /* entryinfo is locked */
            islocked = 1;

            /* If we can successfully writelock it, then
             * the object is idle.
             */
            if ( bdb_cache_entry_db_lock( bdb,
                  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_db_unlock( bdb, lockp );

                  /* 
                   * If it is a leaf node, and we're over the limit, free it.
                   */
                  if ( elru->bei_kids ) {
                        /* Drop from list, we ignore it... */
                        LRU_DEL( &bdb->bi_cache, elru );
                  } else if ( bdb->bi_cache.c_leaves > eimax ) {
                        /* Too many leaf nodes, free this one */
                        bdb_cache_delete_internal( &bdb->bi_cache, elru, 0 );
                        bdb_cache_delete_cleanup( &bdb->bi_cache, elru );
                        islocked = 0;
                  }     /* Leave on list until we need to free it */
            }

            if ( islocked )
                  bdb_cache_entryinfo_unlock( elru );

            if ( count >= bdb->bi_cache.c_minfree ) {
                  ldap_pvt_thread_mutex_lock( &bdb->bi_cache.c_count_mutex );
                  bdb->bi_cache.c_cursize -= count;
                  ldap_pvt_thread_mutex_unlock( &bdb->bi_cache.c_count_mutex );
                  break;
            }
bottom:
            if ( elnext == bdb->bi_cache.c_lruhead )
                  break;
      }

      bdb->bi_cache.c_lruhead = elnext;
      ldap_pvt_thread_mutex_unlock( &bdb->bi_cache.c_lru_mutex );
      bdb->bi_cache.c_purging = 0;
}

EntryInfo *
bdb_cache_find_info(
      struct bdb_info *bdb,
      ID id )
{
      EntryInfo   ei = { 0 },
                  *ei2;

      ei.bei_id = id;

      ldap_pvt_thread_rdwr_rlock( &bdb->bi_cache.c_rwlock );
      ei2 = (EntryInfo *) avl_find( bdb->bi_cache.c_idtree,
                              (caddr_t) &ei, bdb_id_cmp );
      ldap_pvt_thread_rdwr_runlock( &bdb->bi_cache.c_rwlock );
      return ei2;
}

/*
 * cache_find_id - find an entry in the cache, given id.
 * The entry is locked for Read upon return. Call with flag ID_LOCKED if
 * the supplied *eip was already locked.
 */

int
bdb_cache_find_id(
      Operation *op,
      DB_TXN      *tid,
      ID                      id,
      EntryInfo   **eip,
      int         flag,
      BDB_LOCKER  locker,
      DB_LOCK           *lock )
{
      struct bdb_info *bdb = (struct bdb_info *) op->o_bd->be_private;
      Entry *ep = NULL;
      int   rc = 0, load = 0;
      EntryInfo ei = { 0 };

      ei.bei_id = id;

#ifdef SLAP_ZONE_ALLOC
      slap_zh_rlock(bdb->bi_cache.c_zctx);
#endif
      /* If we weren't given any info, see if we have it already cached */
      if ( !*eip ) {
again:      ldap_pvt_thread_rdwr_rlock( &bdb->bi_cache.c_rwlock );
            *eip = (EntryInfo *) avl_find( bdb->bi_cache.c_idtree,
                  (caddr_t) &ei, bdb_id_cmp );
            if ( *eip ) {
                  /* If the lock attempt fails, the info is in use */
                  if ( bdb_cache_entryinfo_trylock( *eip )) {
                        ldap_pvt_thread_rdwr_runlock( &bdb->bi_cache.c_rwlock );
                        /* If this node is being deleted, treat
                         * as if the delete has already finished
                         */
                        if ( (*eip)->bei_state & CACHE_ENTRY_DELETED ) {
                              return DB_NOTFOUND;
                        }
                        /* otherwise, wait for the info to free up */
                        ldap_pvt_thread_yield();
                        goto again;
                  }
                  /* If this info isn't hooked up to its parent yet,
                   * unlock and wait for it to be fully initialized
                   */
                  if ( (*eip)->bei_state & CACHE_ENTRY_NOT_LINKED ) {
                        bdb_cache_entryinfo_unlock( *eip );
                        ldap_pvt_thread_rdwr_runlock( &bdb->bi_cache.c_rwlock );
                        ldap_pvt_thread_yield();
                        goto again;
                  }
                  flag |= ID_LOCKED;
            }
            ldap_pvt_thread_rdwr_runlock( &bdb->bi_cache.c_rwlock );
      }

      /* See if the ID exists in the database; add it to the cache if so */
      if ( !*eip ) {
#ifndef BDB_HIER
            rc = bdb_id2entry( op->o_bd, tid, locker, id, &ep );
            if ( rc == 0 ) {
                  rc = bdb_cache_find_ndn( op, locker,
                        &ep->e_nname, eip );
                  if ( *eip ) flag |= ID_LOCKED;
                  if ( rc ) {
                        ep->e_private = NULL;
#ifdef SLAP_ZONE_ALLOC
                        bdb_entry_return( bdb, ep, (*eip)->bei_zseq );
#else
                        bdb_entry_return( ep );
#endif
                        ep = NULL;
                  }
            }
#else
            rc = hdb_cache_find_parent(op, locker, id, eip );
            if ( rc == 0 ) flag |= ID_LOCKED;
#endif
      }

      /* Ok, we found the info, do we have the entry? */
      if ( rc == 0 ) {
            if ( !( flag & ID_LOCKED )) {
                  bdb_cache_entryinfo_lock( *eip );
                  flag |= ID_LOCKED;
            }

            if ( (*eip)->bei_state & CACHE_ENTRY_DELETED ) {
                  rc = DB_NOTFOUND;
            } else {
                  (*eip)->bei_finders++;
                  (*eip)->bei_state |= CACHE_ENTRY_REFERENCED;
                  /* Make sure only one thread tries to load the entry */
load1:
#ifdef SLAP_ZONE_ALLOC
                  if ((*eip)->bei_e && !slap_zn_validate(
                              bdb->bi_cache.c_zctx, (*eip)->bei_e, (*eip)->bei_zseq)) {
                        (*eip)->bei_e = NULL;
                        (*eip)->bei_zseq = 0;
                  }
#endif
                  if ( !(*eip)->bei_e && !((*eip)->bei_state & CACHE_ENTRY_LOADING)) {
                        load = 1;
                        (*eip)->bei_state |= CACHE_ENTRY_LOADING;
                  }

                  if ( !load ) {
                        /* Clear the uncached state if we are not
                         * loading it, i.e it is already cached or
                         * another thread is currently loading it.
                         */
                        (*eip)->bei_state &= ~CACHE_ENTRY_NOT_CACHED;
                        flag &= ~ID_NOCACHE;
                  }

                  if ( flag & ID_LOCKED ) {
                        bdb_cache_entryinfo_unlock( *eip );
                        flag ^= ID_LOCKED;
                  }
                  rc = bdb_cache_entry_db_lock( bdb, locker, *eip, load, 0, lock );
                  if ( (*eip)->bei_state & CACHE_ENTRY_DELETED ) {
                        rc = DB_NOTFOUND;
                        bdb_cache_entry_db_unlock( bdb, lock );
                  } else if ( rc == 0 ) {
                        if ( load ) {
                              if ( !ep) {
                                    rc = bdb_id2entry( op->o_bd, tid, locker, id, &ep );
                              }
                              if ( rc == 0 ) {
                                    ep->e_private = *eip;
#ifdef BDB_HIER
                                    bdb_fix_dn( ep, 0 );
#endif
                                    (*eip)->bei_e = ep;
#ifdef SLAP_ZONE_ALLOC
                                    (*eip)->bei_zseq = *((ber_len_t *)ep - 2);
#endif
                                    ep = NULL;
                                    bdb_cache_lru_link( bdb, *eip );
                                    if (( flag & ID_NOCACHE ) &&
                                          ( bdb_cache_entryinfo_trylock( *eip ) == 0 )) {
                                          /* Set the cached state only if no other thread
                                           * found the info while we were loading the entry.
                                           */
                                          if ( (*eip)->bei_finders == 1 )
                                                (*eip)->bei_state |= CACHE_ENTRY_NOT_CACHED;
                                          bdb_cache_entryinfo_unlock( *eip );
                                    }
                              }
                              if ( rc == 0 ) {
                                    /* If we succeeded, downgrade back to a readlock. */
                                    rc = bdb_cache_entry_db_relock( bdb, locker,
                                          *eip, 0, 0, lock );
                              } else {
                                    /* Otherwise, release the lock. */
                                    bdb_cache_entry_db_unlock( bdb, lock );
                              }
                        } else if ( !(*eip)->bei_e ) {
                              /* Some other thread is trying to load the entry,
                               * wait for it to finish.
                               */
                              bdb_cache_entry_db_unlock( bdb, lock );
                              bdb_cache_entryinfo_lock( *eip );
                              flag |= ID_LOCKED;
                              goto load1;
#ifdef BDB_HIER
                        } else {
                              /* Check for subtree renames
                               */
                              rc = bdb_fix_dn( (*eip)->bei_e, 1 );
                              if ( rc ) {
                                    bdb_cache_entry_db_relock( bdb,
                                          locker, *eip, 1, 0, lock );
                                    /* check again in case other modifier did it already */
                                    if ( bdb_fix_dn( (*eip)->bei_e, 1 ) )
                                          rc = bdb_fix_dn( (*eip)->bei_e, 2 );
                                    bdb_cache_entry_db_relock( bdb,
                                          locker, *eip, 0, 0, lock );
                              }
#endif
                        }
                  }
                  bdb_cache_entryinfo_lock( *eip );
                  (*eip)->bei_finders--;
                  if ( load )
                        (*eip)->bei_state ^= CACHE_ENTRY_LOADING;
                  bdb_cache_entryinfo_unlock( *eip );
            }
      }
      if ( flag & ID_LOCKED ) {
            bdb_cache_entryinfo_unlock( *eip );
      }
      if ( ep ) {
            ep->e_private = NULL;
#ifdef SLAP_ZONE_ALLOC
            bdb_entry_return( bdb, ep, (*eip)->bei_zseq );
#else
            bdb_entry_return( ep );
#endif
      }
      if ( rc == 0 ) {
            int purge = 0;

            if ( load ) {
                  if ( !( flag & ID_NOCACHE )) {
                        ldap_pvt_thread_mutex_lock( &bdb->bi_cache.c_count_mutex );
                        bdb->bi_cache.c_cursize++;
                        if ( bdb->bi_cache.c_cursize > bdb->bi_cache.c_maxsize &&
                              !bdb->bi_cache.c_purging ) {
                              purge = 1;
                              bdb->bi_cache.c_purging = 1;
                        }
                        ldap_pvt_thread_mutex_unlock( &bdb->bi_cache.c_count_mutex );
                  }
            }
            if ( purge )
                  bdb_cache_lru_purge( bdb );
      }

#ifdef SLAP_ZONE_ALLOC
      if (rc == 0 && (*eip)->bei_e) {
            slap_zn_rlock(bdb->bi_cache.c_zctx, (*eip)->bei_e);
      }
      slap_zh_runlock(bdb->bi_cache.c_zctx);
#endif
      return rc;
}

int
bdb_cache_children(
      Operation *op,
      DB_TXN *txn,
      Entry *e )
{
      int rc;

      if ( BEI(e)->bei_kids ) {
            return 0;
      }
      if ( BEI(e)->bei_state & CACHE_ENTRY_NO_KIDS ) {
            return DB_NOTFOUND;
      }
      rc = bdb_dn2id_children( op, txn, e );
      if ( rc == DB_NOTFOUND ) {
            BEI(e)->bei_state |= CACHE_ENTRY_NO_KIDS | CACHE_ENTRY_NO_GRANDKIDS;
      }
      return rc;
}

/* Update the cache after a successful database Add. */
int
bdb_cache_add(
      struct bdb_info *bdb,
      EntryInfo *eip,
      Entry *e,
      struct berval *nrdn,
      BDB_LOCKER locker,
      DB_LOCK *lock )
{
      EntryInfo *new, ei;
      int rc, purge = 0;
#ifdef BDB_HIER
      struct berval rdn = e->e_name;
#endif

      ei.bei_id = e->e_id;
      ei.bei_parent = eip;
      ei.bei_nrdn = *nrdn;
      ei.bei_lockpad = 0;

      /* Lock this entry so that bdb_add can run to completion.
       * It can only fail if BDB has run out of lock resources.
       */
      rc = bdb_cache_entry_db_lock( bdb, locker, &ei, 0, 0, lock );
      if ( rc ) {
            bdb_cache_entryinfo_unlock( eip );
            return rc;
      }

#ifdef BDB_HIER
      if ( nrdn->bv_len != e->e_nname.bv_len ) {
            char *ptr = ber_bvchr( &rdn, ',' );
            assert( ptr != NULL );
            rdn.bv_len = ptr - rdn.bv_val;
      }
      ber_dupbv( &ei.bei_rdn, &rdn );
      if ( eip->bei_dkids ) eip->bei_dkids++;
#endif

      rc = bdb_entryinfo_add_internal( bdb, &ei, &new );
      /* bdb_csn_commit can cause this when adding the database root entry */
      if ( new->bei_e ) {
            new->bei_e->e_private = NULL;
#ifdef SLAP_ZONE_ALLOC
            bdb_entry_return( bdb, new->bei_e, new->bei_zseq );
#else
            bdb_entry_return( new->bei_e );
#endif
      }
      new->bei_e = e;
      e->e_private = new;
      new->bei_state |= CACHE_ENTRY_NO_KIDS | CACHE_ENTRY_NO_GRANDKIDS;
      eip->bei_state &= ~CACHE_ENTRY_NO_KIDS;
      if (eip->bei_parent) {
            eip->bei_parent->bei_state &= ~CACHE_ENTRY_NO_GRANDKIDS;
      }
      bdb_cache_entryinfo_unlock( eip );

      ldap_pvt_thread_rdwr_wunlock( &bdb->bi_cache.c_rwlock );
      ldap_pvt_thread_mutex_lock( &bdb->bi_cache.c_count_mutex );
      ++bdb->bi_cache.c_cursize;
      if ( bdb->bi_cache.c_cursize > bdb->bi_cache.c_maxsize &&
            !bdb->bi_cache.c_purging ) {
            purge = 1;
            bdb->bi_cache.c_purging = 1;
      }
      ldap_pvt_thread_mutex_unlock( &bdb->bi_cache.c_count_mutex );

      bdb_cache_lru_link( bdb, new );

      if ( purge )
            bdb_cache_lru_purge( bdb );

      return rc;
}

int
bdb_cache_modify(
      struct bdb_info *bdb,
      Entry *e,
      Attribute *newAttrs,
      BDB_LOCKER locker,
      DB_LOCK *lock )
{
      EntryInfo *ei = BEI(e);
      int rc;
      /* Get write lock on data */
      rc = bdb_cache_entry_db_relock( bdb, locker, ei, 1, 0, lock );

      /* If we've done repeated mods on a cached entry, then e_attrs
       * is no longer contiguous with the entry, and must be freed.
       */
      if ( ! rc ) {
            if ( (void *)e->e_attrs != (void *)(e+1) ) {
                  attrs_free( e->e_attrs ); 
            }
            e->e_attrs = newAttrs;
      }
      return rc;
}

/*
 * Change the rdn in the entryinfo. Also move to a new parent if needed.
 */
int
bdb_cache_modrdn(
      struct bdb_info *bdb,
      Entry *e,
      struct berval *nrdn,
      Entry *new,
      EntryInfo *ein,
      BDB_LOCKER locker,
      DB_LOCK *lock )
{
      EntryInfo *ei = BEI(e), *pei;
      int rc;
#ifdef BDB_HIER
      struct berval rdn;
#endif

      /* Get write lock on data */
      rc =  bdb_cache_entry_db_relock( bdb, locker, ei, 1, 0, lock );
      if ( rc ) return rc;

      /* If we've done repeated mods on a cached entry, then e_attrs
       * is no longer contiguous with the entry, and must be freed.
       */
      if ( (void *)e->e_attrs != (void *)(e+1) ) {
            attrs_free( e->e_attrs );
      }
      e->e_attrs = new->e_attrs;
      if( e->e_nname.bv_val < e->e_bv.bv_val ||
            e->e_nname.bv_val > e->e_bv.bv_val + e->e_bv.bv_len )
      {
            ch_free(e->e_name.bv_val);
            ch_free(e->e_nname.bv_val);
      }
      e->e_name = new->e_name;
      e->e_nname = new->e_nname;

      /* Lock the parent's kids AVL tree */
      pei = ei->bei_parent;
      bdb_cache_entryinfo_lock( pei );
      avl_delete( &pei->bei_kids, (caddr_t) ei, bdb_rdn_cmp );
      free( ei->bei_nrdn.bv_val );
      ber_dupbv( &ei->bei_nrdn, nrdn );

#ifdef BDB_HIER
      free( ei->bei_rdn.bv_val );

      rdn = e->e_name;
      if ( nrdn->bv_len != e->e_nname.bv_len ) {
            char *ptr = ber_bvchr(&rdn, ',');
            assert( ptr != NULL );
            rdn.bv_len = ptr - rdn.bv_val;
      }
      ber_dupbv( &ei->bei_rdn, &rdn );

      /* If new parent, decrement kid counts */
      if ( ein ) {
            pei->bei_ckids--;
            if ( pei->bei_dkids ) {
                  pei->bei_dkids--;
                  if ( pei->bei_dkids < 2 )
                        pei->bei_state |= CACHE_ENTRY_NO_KIDS | CACHE_ENTRY_NO_GRANDKIDS;
            }
      }
#endif

      if (!ein) {
            ein = ei->bei_parent;
      } else {
            ei->bei_parent = ein;
            bdb_cache_entryinfo_unlock( pei );
            bdb_cache_entryinfo_lock( ein );

            /* new parent now has kids */
            if ( ein->bei_state & CACHE_ENTRY_NO_KIDS )
                  ein->bei_state ^= CACHE_ENTRY_NO_KIDS;
            /* grandparent has grandkids */
            if ( ein->bei_parent )
                  ein->bei_parent->bei_state &= ~CACHE_ENTRY_NO_GRANDKIDS;
#ifdef BDB_HIER
            /* parent might now have grandkids */
            if ( ein->bei_state & CACHE_ENTRY_NO_GRANDKIDS &&
                  !(ei->bei_state & CACHE_ENTRY_NO_KIDS))
                  ein->bei_state ^= CACHE_ENTRY_NO_GRANDKIDS;

            ein->bei_ckids++;
            if ( ein->bei_dkids ) ein->bei_dkids++;
#endif
      }

#ifdef BDB_HIER
      /* Record the generation number of this change */
      ldap_pvt_thread_mutex_lock( &bdb->bi_modrdns_mutex );
      bdb->bi_modrdns++;
      ei->bei_modrdns = bdb->bi_modrdns;
      ldap_pvt_thread_mutex_unlock( &bdb->bi_modrdns_mutex );
#endif

      avl_insert( &ein->bei_kids, ei, bdb_rdn_cmp, avl_dup_error );
      bdb_cache_entryinfo_unlock( ein );
      return rc;
}
/*
 * cache_delete - delete the entry e from the cache. 
 *
 * returns: 0     e was deleted ok
 *          1     e was not in the cache
 *          -1    something bad happened
 */
int
bdb_cache_delete(
      struct bdb_info *bdb,
    Entry         *e,
    BDB_LOCKER    locker,
    DB_LOCK *lock )
{
      EntryInfo *ei = BEI(e);
      int   rc;

      assert( e->e_private != NULL );

      /* Lock the entry's info */
      bdb_cache_entryinfo_lock( ei );

      /* Set this early, warn off any queriers */
      ei->bei_state |= CACHE_ENTRY_DELETED;

      bdb_cache_entryinfo_unlock( ei );

      /* Get write lock on the data */
      rc = bdb_cache_entry_db_relock( bdb, locker, ei, 1, 0, lock );
      if ( rc ) {
            /* couldn't lock, undo and give up */
            ei->bei_state ^= CACHE_ENTRY_DELETED;
            return rc;
      }

      Debug( LDAP_DEBUG_TRACE, "====> bdb_cache_delete( %ld )\n",
            e->e_id, 0, 0 );

      /* set lru mutex */
      ldap_pvt_thread_mutex_lock( &bdb->bi_cache.c_lru_mutex );

      rc = bdb_cache_delete_internal( &bdb->bi_cache, e->e_private, 1 );

      /* free lru mutex */
      ldap_pvt_thread_mutex_unlock( &bdb->bi_cache.c_lru_mutex );

      return( rc );
}

void
bdb_cache_delete_cleanup(
      Cache *cache,
      EntryInfo *ei )
{
      /* Enter with ei locked */

      if ( ei->bei_e ) {
            ei->bei_e->e_private = NULL;
#ifdef SLAP_ZONE_ALLOC
            bdb_entry_return( ei->bei_bdb, ei->bei_e, ei->bei_zseq );
#else
            bdb_entry_return( ei->bei_e );
#endif
            ei->bei_e = NULL;
      }

      bdb_cache_entryinfo_free( cache, ei );
      bdb_cache_entryinfo_unlock( ei );
}

static int
bdb_cache_delete_internal(
    Cache   *cache,
    EntryInfo           *e,
    int           decr )
{
      int rc = 0; /* return code */
      int decr_leaf = 0;

      /* Lock the parent's kids tree */
      bdb_cache_entryinfo_lock( e->bei_parent );

#ifdef BDB_HIER
      e->bei_parent->bei_ckids--;
      if ( decr && e->bei_parent->bei_dkids ) e->bei_parent->bei_dkids--;
#endif
      /* dn tree */
      if ( avl_delete( &e->bei_parent->bei_kids, (caddr_t) e, bdb_rdn_cmp )
            == NULL )
      {
            rc = -1;
      }
      if ( e->bei_parent->bei_kids )
            decr_leaf = 1;

      bdb_cache_entryinfo_unlock( e->bei_parent );

      ldap_pvt_thread_rdwr_wlock( &cache->c_rwlock );
      /* id tree */
      if ( avl_delete( &cache->c_idtree, (caddr_t) e, bdb_id_cmp )) {
            cache->c_eiused--;
            if ( decr_leaf )
                  cache->c_leaves--;
      } else {
            rc = -1;
      }
      ldap_pvt_thread_rdwr_wunlock( &cache->c_rwlock );

      if ( rc == 0 ){
            /* lru */
            LRU_DEL( cache, e );

            if ( e->bei_e ) {
                  ldap_pvt_thread_mutex_lock( &cache->c_count_mutex );
                  cache->c_cursize--;
                  ldap_pvt_thread_mutex_unlock( &cache->c_count_mutex );
            }
      }

      return( rc );
}

static void
bdb_entryinfo_release( void *data )
{
      EntryInfo *ei = (EntryInfo *)data;
      if ( ei->bei_kids ) {
            avl_free( ei->bei_kids, NULL );
      }
      if ( ei->bei_e ) {
            ei->bei_e->e_private = NULL;
#ifdef SLAP_ZONE_ALLOC
            bdb_entry_return( ei->bei_bdb, ei->bei_e, ei->bei_zseq );
#else
            bdb_entry_return( ei->bei_e );
#endif
      }
      bdb_cache_entryinfo_destroy( ei );
}

void
bdb_cache_release_all( Cache *cache )
{
      /* set cache write lock */
      ldap_pvt_thread_rdwr_wlock( &cache->c_rwlock );
      /* set lru mutex */
      ldap_pvt_thread_mutex_lock( &cache->c_lru_mutex );

      Debug( LDAP_DEBUG_TRACE, "====> bdb_cache_release_all\n", 0, 0, 0 );

      avl_free( cache->c_dntree.bei_kids, NULL );
      avl_free( cache->c_idtree, bdb_entryinfo_release );
      for (;cache->c_eifree;cache->c_eifree = cache->c_lruhead) {
            cache->c_lruhead = cache->c_eifree->bei_lrunext;
            bdb_cache_entryinfo_destroy(cache->c_eifree);
      }
      cache->c_cursize = 0;
      cache->c_eiused = 0;
      cache->c_leaves = 0;
      cache->c_idtree = NULL;
      cache->c_lruhead = NULL;
      cache->c_lrutail = NULL;
      cache->c_dntree.bei_kids = NULL;

      /* free lru mutex */
      ldap_pvt_thread_mutex_unlock( &cache->c_lru_mutex );
      /* free cache write lock */
      ldap_pvt_thread_rdwr_wunlock( &cache->c_rwlock );
}

#ifdef LDAP_DEBUG
#ifdef SLAPD_UNUSED
static void
bdb_lru_print( Cache *cache )
{
      EntryInfo   *e;

      fprintf( stderr, "LRU circle head: %p\n", (void *) cache->c_lruhead );
      fprintf( stderr, "LRU circle (tail forward):\n" );
      for ( e = cache->c_lrutail; ; ) {
            fprintf( stderr, "\t%p, %p id %ld rdn \"%s\"\n",
                  (void *) e, (void *) e->bei_e, e->bei_id, e->bei_nrdn.bv_val );
            e = e->bei_lrunext;
            if ( e == cache->c_lrutail )
                  break;
      }
      fprintf( stderr, "LRU circle (tail backward):\n" );
      for ( e = cache->c_lrutail; ; ) {
            fprintf( stderr, "\t%p, %p id %ld rdn \"%s\"\n",
                  (void *) e, (void *) e->bei_e, e->bei_id, e->bei_nrdn.bv_val );
            e = e->bei_lruprev;
            if ( e == cache->c_lrutail )
                  break;
      }
}
#endif
#endif

#ifdef BDB_REUSE_LOCKERS
static void
bdb_locker_id_free( void *key, void *data )
{
      DB_ENV *env = key;
      u_int32_t lockid;
      int rc;

#if DB_VERSION_FULL >= 0x04060012
      BDB_LOCKER lptr = data;
      lockid = lptr->id;
#else
      lockid = (long)data;
#endif
      rc = XLOCK_ID_FREE( env, lockid );
      if ( rc == EINVAL ) {
            DB_LOCKREQ lr;
            Debug( LDAP_DEBUG_ANY,
                  "bdb_locker_id_free: %lu err %s(%d)\n",
                  (unsigned long) lockid, db_strerror(rc), rc );
            /* release all locks held by this locker. */
            lr.op = DB_LOCK_PUT_ALL;
            lr.obj = NULL;
            env->lock_vec( env, lockid, 0, &lr, 1, NULL );
            XLOCK_ID_FREE( env, lockid );
      }
}

/* free up any keys used by the main thread */
void
bdb_locker_flush( DB_ENV *env )
{
      void *data;
      void *ctx = ldap_pvt_thread_pool_context();

      if ( !ldap_pvt_thread_pool_getkey( ctx, env, &data, NULL ) ) {
            ldap_pvt_thread_pool_setkey( ctx, env, NULL, 0, NULL, NULL );
            bdb_locker_id_free( env, data );
      }
}

int
bdb_locker_id( Operation *op, DB_ENV *env, BDB_LOCKER *locker )
{
      int i, rc;
      u_int32_t lockid;
      void *data;
      void *ctx;

      if ( !env || !locker ) return -1;

      /* If no op was provided, try to find the ctx anyway... */
      if ( op ) {
            ctx = op->o_threadctx;
      } else {
            ctx = ldap_pvt_thread_pool_context();
      }

      /* Shouldn't happen unless we're single-threaded */
      if ( !ctx ) {
            *locker = 0;
            return 0;
      }

      if ( ldap_pvt_thread_pool_getkey( ctx, env, &data, NULL ) ) {
            for ( i=0, rc=1; rc != 0 && i<4; i++ ) {
                  rc = XLOCK_ID( env, &lockid );
                  if (rc) ldap_pvt_thread_yield();
            }
            if ( rc != 0) {
                  return rc;
            }
#if DB_VERSION_FULL >= 0x04060012
            { BDB_LOCKER lptr;
            __lock_getlocker( env->lk_handle, lockid, 0, &lptr );
            data = lptr;
            }
#else
            data = (void *)((long)lockid);
#endif
            if ( ( rc = ldap_pvt_thread_pool_setkey( ctx, env,
                  data, bdb_locker_id_free, NULL, NULL ) ) ) {
                  XLOCK_ID_FREE( env, lockid );
                  Debug( LDAP_DEBUG_ANY, "bdb_locker_id: err %s(%d)\n",
                        db_strerror(rc), rc, 0 );

                  return rc;
            }
      } else {
            lockid = (long)data;
      }
#if DB_VERSION_FULL >= 0x04060012
      *locker = data;
#else
      *locker = lockid;
#endif
      return 0;
}
#endif /* BDB_REUSE_LOCKERS */

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