BUG/MEDIUM: memory_pool: Update the seq number in pool_flush().
In pool_flush(), we can't just set the free_list to NULL, or we may suffer
the ABA problem. Instead, use a double-width CAS and update the sequence
number.
This should be backported to 2.1, 2.0 and 1.9.
This may, or may not, be related to github issue #476.
diff --git a/src/memory.c b/src/memory.c
index a858a09..24d709f 100644
--- a/src/memory.c
+++ b/src/memory.c
@@ -217,15 +217,20 @@
*/
void pool_flush(struct pool_head *pool)
{
+ struct pool_free_list cmp, new;
void **next, *temp;
int removed = 0;
if (!pool)
return;
do {
- next = pool->free_list;
- } while (!_HA_ATOMIC_CAS(&pool->free_list, &next, NULL));
+ cmp.free_list = pool->free_list;
+ cmp.seq = pool->seq;
+ new.free_list = NULL;
+ new.seq = cmp.seq + 1;
+ } while (!_HA_ATOMIC_DWCAS(&pool->free_list, &cmp, &new));
__ha_barrier_atomic_store();
+ next = cmp.free_list;
while (next) {
temp = next;
next = *POOL_LINK(pool, temp);