Fix: hash table growth (for small tables) should be limited

[urcu.git] / rculfhash.c

diff --git a/rculfhash.c b/rculfhash.c
index 6e12db1013f6c58d70ee3119a67a068fadc3d80e..7d39388f494700a1b06a5df885d5a5350cdf42a8 100644 (file)
--- a/rculfhash.c
+++ b/rculfhash.c
@@ -563,6 +563,7 @@ void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
 
 static long nr_cpus_mask = -1;
 static long split_count_mask = -1;
+static int split_count_order = -1;
 
 #if defined(HAVE_SYSCONF)
 static void ht_init_nr_cpus_mask(void)
@@ -597,6 +598,8 @@ void alloc_split_items_count(struct cds_lfht *ht)
                        split_count_mask = DEFAULT_SPLIT_COUNT_MASK;
                else
                        split_count_mask = nr_cpus_mask;
+               split_count_order =
+                       cds_lfht_get_count_order_ulong(split_count_mask + 1);
        }
 
        assert(split_count_mask >= 0);
@@ -713,14 +716,39 @@ void check_resize(struct cds_lfht *ht, unsigned long size, uint32_t chain_len)
         * Use bucket-local length for small table expand and for
         * environments lacking per-cpu data support.
         */
-       if (count >= (1UL << COUNT_COMMIT_ORDER))
+       if (count >= (1UL << (COUNT_COMMIT_ORDER + split_count_order)))
                return;
        if (chain_len > 100)
                dbg_printf("WARNING: large chain length: %u.\n",
                           chain_len);
-       if (chain_len >= CHAIN_LEN_RESIZE_THRESHOLD)
-               cds_lfht_resize_lazy_grow(ht, size,
-                       cds_lfht_get_count_order_u32(chain_len - (CHAIN_LEN_TARGET - 1)));
+       if (chain_len >= CHAIN_LEN_RESIZE_THRESHOLD) {
+               int growth;
+
+               /*
+                * Ideal growth calculated based on chain length.
+                */
+               growth = cds_lfht_get_count_order_u32(chain_len
+                               - (CHAIN_LEN_TARGET - 1));
+               if ((ht->flags & CDS_LFHT_ACCOUNTING)
+                               && (size << growth)
+                                       >= (1UL << (COUNT_COMMIT_ORDER
+                                               + split_count_order))) {
+                       /*
+                        * If ideal growth expands the hash table size
+                        * beyond the "small hash table" sizes, use the
+                        * maximum small hash table size to attempt
+                        * expanding the hash table. This only applies
+                        * when node accounting is available, otherwise
+                        * the chain length is used to expand the hash
+                        * table in every case.
+                        */
+                       growth = COUNT_COMMIT_ORDER + split_count_order
+                               - cds_lfht_get_count_order_ulong(size);
+                       if (growth <= 0)
+                               return;
+               }
+               cds_lfht_resize_lazy_grow(ht, size, growth);
+       }
 }
 
 static
@@ -1745,6 +1773,13 @@ int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr)
        was_online = ht->flavor->read_ongoing();
        if (was_online)
                ht->flavor->thread_offline();
+       /* Calling with RCU read-side held is an error. */
+       if (ht->flavor->read_ongoing()) {
+               ret = -EINVAL;
+               if (was_online)
+                       ht->flavor->thread_online();
+               goto end;
+       }
        while (uatomic_read(&ht->in_progress_resize))
                poll(NULL, 0, 100);     /* wait for 100ms */
        if (was_online)
@@ -1756,6 +1791,7 @@ int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr)
        if (attr)
                *attr = ht->resize_attr;
        poison_free(ht);
+end:
        return ret;
 }
 
@@ -1886,14 +1922,26 @@ void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size)
 {
        int was_online;
 
-       resize_target_update_count(ht, new_size);
-       CMM_STORE_SHARED(ht->resize_initiated, 1);
        was_online = ht->flavor->read_ongoing();
        if (was_online)
                ht->flavor->thread_offline();
+       /* Calling with RCU read-side held is an error. */
+       if (ht->flavor->read_ongoing()) {
+               static int print_once;
+
+               if (!CMM_LOAD_SHARED(print_once))
+                       fprintf(stderr, "[error] rculfhash: cds_lfht_resize "
+                               "called with RCU read-side lock held.\n");
+               CMM_STORE_SHARED(print_once, 1);
+               assert(0);
+               goto end;
+       }
+       resize_target_update_count(ht, new_size);
+       CMM_STORE_SHARED(ht->resize_initiated, 1);
        pthread_mutex_lock(&ht->resize_mutex);
        _do_cds_lfht_resize(ht);
        pthread_mutex_unlock(&ht->resize_mutex);
+end:
        if (was_online)
                ht->flavor->thread_online();
 }