ITS#9529 pcache: fix consistency_check locking

diff --git a/servers/slapd/overlays/pcache.c b/servers/slapd/overlays/pcache.c
index f7b3f4372e68276c8b341c17520447f59bf4cc74..8d45ed9aef9cb3809e6cb39f6f08aec172a950ab 100644 (file)
--- a/servers/slapd/overlays/pcache.c
+++ b/servers/slapd/overlays/pcache.c
@@ -87,6 +87,7 @@ typedef struct cached_query_s {
        int                                             bind_refcnt;    /* number of bind operation referencing this query */
        unsigned long                   answerable_cnt; /* how many times it was answerable */
        int                                             refcnt; /* references since last refresh */
+       int                                             in_lru; /* query is in LRU list */
        ldap_pvt_thread_mutex_t         answerable_cnt_mutex;
        struct cached_query_s           *next;          /* next query in the template */
        struct cached_query_s           *prev;          /* previous query in the template */
@@ -1044,6 +1045,7 @@ add_query_on_top (query_manager* qm, CachedQuery* qc)
 {
        CachedQuery* top = qm->lru_top;
 
+       qc->in_lru = 1;
        qm->lru_top = qc;
 
        if (top)
@@ -1065,9 +1067,10 @@ remove_query (query_manager* qm, CachedQuery* qc)
        CachedQuery* up;
        CachedQuery* down;
 
-       if (!qc)
+       if (!qc || !qc->in_lru)
                return;
 
+       qc->in_lru = 0;
        up = qc->lru_up;
        down = qc->lru_down;
 
@@ -3515,6 +3518,7 @@ consistency_check(
        Operation *op;
 
        CachedQuery *query, *qprev;
+       CachedQuery *expires = NULL;
        int return_val, pause = PCACHE_CC_PAUSED;
        QueryTemplate *templ;
 
@@ -3548,6 +3552,9 @@ consistency_check(
                        ttl += op->o_time;
                }
 
+               Debug( pcache_debug, "Lock CR index = %p\n",
+                               (void *) templ, 0, 0 );
+               ldap_pvt_thread_rdwr_wlock(&templ->t_rwlock);
                for ( query=templ->query_last; query; query=qprev ) {
                        qprev = query->prev;
                        if ( query->refresh_time && query->refresh_time < op->o_time ) {
@@ -3559,56 +3566,29 @@ consistency_check(
                                if ( query->refcnt )
                                        query->expiry_time = op->o_time + templ->ttl;
                                if ( query->expiry_time > op->o_time ) {
-                                       refresh_query( op, query, on );
+                                       /* perform actual refresh below */
                                        continue;
                                }
                        }
 
                        if (query->expiry_time < op->o_time) {
                                int rem = 0;
-                               Debug( pcache_debug, "Lock CR index = %p\n",
-                                               (void *) templ, 0, 0 );
-                               ldap_pvt_thread_rdwr_wlock(&templ->t_rwlock);
-                               if ( query == templ->query_last ) {
-                                       rem = 1;
-                                       remove_from_template(query, templ);
-                                       Debug( pcache_debug, "TEMPLATE %p QUERIES-- %d\n",
-                                                       (void *) templ, templ->no_of_queries, 0 );
-                                       Debug( pcache_debug, "Unlock CR index = %p\n",
-                                                       (void *) templ, 0, 0 );
-                               }
-                               if ( !rem ) {
-                                       ldap_pvt_thread_rdwr_wunlock(&templ->t_rwlock);
+                               if ( query != templ->query_last )
                                        continue;
-                               }
                                ldap_pvt_thread_mutex_lock(&qm->lru_mutex);
-                               remove_query(qm, query);
-                               ldap_pvt_thread_mutex_unlock(&qm->lru_mutex);
-                               if ( BER_BVISNULL( &query->q_uuid ))
-                                       return_val = 0;
-                               else
-                                       return_val = remove_query_data(op, &query->q_uuid);
-                               Debug( pcache_debug, "STALE QUERY REMOVED, SIZE=%d\n",
-                                                       return_val, 0, 0 );
-                               ldap_pvt_thread_mutex_lock(&cm->cache_mutex);
-                               cm->cur_entries -= return_val;
-                               cm->num_cached_queries--;
-                               Debug( pcache_debug, "STORED QUERIES = %lu\n",
-                                               cm->num_cached_queries, 0, 0 );
-                               ldap_pvt_thread_mutex_unlock(&cm->cache_mutex);
-                               Debug( pcache_debug,
-                                       "STALE QUERY REMOVED, CACHE ="
-                                       "%d entries\n",
-                                       cm->cur_entries, 0, 0 );
-                               ldap_pvt_thread_rdwr_wlock( &query->rwlock );
-                               if ( query->bind_refcnt-- ) {
-                                       rem = 0;
-                               } else {
+                               if (query->in_lru) {
+                                       remove_query(qm, query);
                                        rem = 1;
                                }
-                               ldap_pvt_thread_rdwr_wunlock( &query->rwlock );
-                               if ( rem ) free_query(query);
-                               ldap_pvt_thread_rdwr_wunlock(&templ->t_rwlock);
+                               ldap_pvt_thread_mutex_unlock(&qm->lru_mutex);
+                               if (!rem)
+                                       continue;
+                               remove_from_template(query, templ);
+                               Debug( pcache_debug, "TEMPLATE %p QUERIES-- %d\n",
+                                               (void *) templ, templ->no_of_queries, 0 );
+                               query->prev = expires;
+                               expires = query;
+                               query->qtemp = NULL;
                        } else if ( !templ->ttr && query->expiry_time > ttl ) {
                                /* We don't need to check for refreshes, and this
                                 * query's expiry is too new, and all subsequent queries
@@ -3620,6 +3600,56 @@ consistency_check(
                                break;
                        }
                }
+               Debug( pcache_debug, "Unlock CR index = %p\n",
+                               (void *) templ, 0, 0 );
+               ldap_pvt_thread_rdwr_wunlock(&templ->t_rwlock);
+               for ( query=expires; query; query=qprev ) {
+                       int rem;
+                       qprev = query->prev;
+                       if ( BER_BVISNULL( &query->q_uuid ))
+                               return_val = 0;
+                       else
+                               return_val = remove_query_data(op, &query->q_uuid);
+                       Debug( pcache_debug, "STALE QUERY REMOVED, SIZE=%d\n",
+                                               return_val, 0, 0 );
+                       ldap_pvt_thread_mutex_lock(&cm->cache_mutex);
+                       cm->cur_entries -= return_val;
+                       cm->num_cached_queries--;
+                       Debug( pcache_debug, "STORED QUERIES = %lu\n",
+                                       cm->num_cached_queries, 0, 0 );
+                       ldap_pvt_thread_mutex_unlock(&cm->cache_mutex);
+                       Debug( pcache_debug,
+                               "STALE QUERY REMOVED, CACHE ="
+                               "%d entries\n",
+                               cm->cur_entries, 0, 0 );
+                       ldap_pvt_thread_rdwr_wlock( &query->rwlock );
+                       if ( query->bind_refcnt-- ) {
+                               rem = 0;
+                       } else {
+                               rem = 1;
+                       }
+                       ldap_pvt_thread_rdwr_wunlock( &query->rwlock );
+                       if ( rem ) free_query(query);
+               }
+
+               /* handle refreshes that we skipped earlier */
+               if ( templ->ttr ) {
+                       ldap_pvt_thread_rdwr_rlock(&templ->t_rwlock);
+                       for ( query=templ->query_last; query; query=qprev ) {
+                               qprev = query->prev;
+                               if ( query->refresh_time && query->refresh_time < op->o_time ) {
+                                       /* A refresh will extend the expiry if the query has been
+                                        * referenced, but not if it's unreferenced. If the
+                                        * expiration has been hit, then skip the refresh since
+                                        * we're just going to discard the result anyway.
+                                        */
+                                       if ( query->expiry_time > op->o_time ) {
+                                               refresh_query( op, query, on );
+                                       }
+                               }
+                       }
+                       ldap_pvt_thread_rdwr_runlock(&templ->t_rwlock);
+               }
        }
 
 leave: