There is a potential race condition between readers and the rehasher.
In particular, the rehasher could have started a rehash while the
reader finishes a scan of the old table but fails to see the new
table pointer.
This patch closes this window by adding smp_wmb/smp_rmb.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
*/
rcu_assign_pointer(ht->future_tbl, new_tbl);
+ /* Ensure the new table is visible to readers. */
+ smp_wmb();
+
for (old_hash = 0; old_hash < old_tbl->size; old_hash++)
rhashtable_rehash_chain(ht, old_hash);
return rht_obj(ht, he);
}
+ /* Ensure we see any new tables. */
+ smp_rmb();
+
old_tbl = tbl;
tbl = rht_dereference_rcu(ht->future_tbl, ht);
if (unlikely(tbl != old_tbl))