[Mesa-dev] [PATCH 2/3] util/set: Do a full search when adding new items

[Jason Ekstrand]

Previously, the set_insert function would bail early if it found a deleted
slot that it could re-use.  However, this is a problem if the key being
inserted is already in the set but further down the list.  If this happens,
the element ends up getting inserted in the set twice.  This commit makes
it so that we walk over all of the possible entries for the given key and
then, if we don't find the key, place it in the available free entry we
found.
---
 src/util/set.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/src/util/set.c b/src/util/set.c
index c3252a0..f01f869 100644
--- a/src/util/set.c
+++ b/src/util/set.c
@@ -251,6 +251,7 @@ static struct set_entry *
 set_add(struct set *ht, uint32_t hash, const void *key)
 {
    uint32_t hash_address;
+   struct set_entry *available_entry = NULL;
 
    if (ht->entries >= ht->max_entries) {
       set_rehash(ht, ht->size_index + 1);
@@ -264,12 +265,11 @@ set_add(struct set *ht, uint32_t hash, const void *key)
       uint32_t double_hash;
 
       if (!entry_is_present(entry)) {
-         if (entry_is_deleted(entry))
-            ht->deleted_entries--;
-         entry->hash = hash;
-         entry->key = key;
-         ht->entries++;
-         return entry;
+         /* Stash the first available entry we find */
+         if (available_entry == NULL)
+            available_entry = entry;
+         if (entry_is_free(entry))
+            break;
       }
 
       /* Implement replacement when another insert happens
@@ -293,6 +293,15 @@ set_add(struct set *ht, uint32_t hash, const void *key)
       hash_address = (hash_address + double_hash) % ht->size;
    } while (hash_address != hash % ht->size);
 
+   if (available_entry) {
+      if (entry_is_deleted(available_entry))
+         ht->deleted_entries--;
+      available_entry->hash = hash;
+      available_entry->key = key;
+      ht->entries++;
+      return available_entry;
+   }
+
    /* We could hit here if a required resize failed. An unchecked-malloc
     * application could ignore this result.
     */
-- 
2.2.2