Use correct release semantic in list update.

nscd uses lockfree lists and we need to ensure the correct release
semantics is used when adding to the list.
(cherry picked from commit 50158f95525ca59459a90f2a7bc65ceb892a0807)

diff --git a/ChangeLog b/ChangeLog
index 34a5ad631c996b7a0e0748fe955c7aa0989730dc..c71653d3f2046a681dbfd1008876254491366b48 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,4 +1,10 @@
 2009-07-16  Ulrich Drepper  <drepper@redhat.com>
+
+       * nscd/cache.c (cache_add): Use atomic_compare_and_exchange_bool_rel
+       instead of atomic_compare_and_exchange_bool_acq to ensure pointer
+       is written before the list head update.
+       Patch by Andreas Schwab <aschwab@redhat.com>.
+
            Jakub Jelinek  <jakub@redhat.com>
 
        * malloc/malloc.c [ATOMIC_FASTBINS] (_int_free): Make check for

diff --git a/nscd/cache.c b/nscd/cache.c
index ab842efc29f25002ea4dc7d61b24ed9f49caf96e..3e6793df2f7dfc2bc3616345fb0cec2a6137c160 100644 (file)
--- a/nscd/cache.c
+++ b/nscd/cache.c
@@ -179,7 +179,7 @@ cache_add (int type, const void *key, size_t len, struct datahead *packet,
   /* Put the new entry in the first position.  */
   do
     newp->next = table->head->array[hash];
-  while (atomic_compare_and_exchange_bool_acq (&table->head->array[hash],
+  while (atomic_compare_and_exchange_bool_rel (&table->head->array[hash],
                                               (ref_t) ((char *) newp
                                                        - table->data),
                                               (ref_t) newp->next));