[PATCH dpdk v3 0/2] hash: safe data replacement on overwrite

[Robin Jarry <rjarry@redhat.com>]

When rte_hash_add_key_data() is called with an existing key, the old
data pointer is silently overwritten. With RCU-protected readers still
potentially accessing the old data, the application cannot safely free
it since the old pointer is never returned.

This series fixes the issue in two places:

* When RCU is configured with a free_key_data_func callback,
  rte_hash_add_key_data() now automatically defers freeing the old data
  on overwrite. No caller changes are needed.

* If rte_hash_del_key() fails to enqueue the deleted entry in
  RTE_HASH_QSBR_MODE_DQ, it falls back on RTE_HASH_QSBR_MODE_SYNC to
  avoid leaking slots and data pointers.

v3:

* Use rte_atomic_exchange_explicit() to swap the new data pointer with
  the old one in search_and_update().

* Removed the rte_hash_replace_key_data() API which required to bubble
  a potential old_data pointer from search_and_update() to all
  intermediate callers down to __rte_hash_add_key_with_hash(). It made
  an already complex code even more obscure.

v2:

* New patch to fallback to SYNC mode when DQ fails on delete.
* Check key_idx == EMPTY_SLOT in DQ mode to differentiate when old_data
  is NULL.
* Also fallback to SYNC mode when DQ fails on replace.

Robin Jarry (2):
  hash: avoid leaking entries on RCU defer queue failure
  hash: free replaced data on overwrite when RCU is configured

 app/test/test_hash.c                   | 134 +++++++++++++++++++++++++
 doc/guides/rel_notes/release_26_03.rst |   7 ++
 lib/hash/rte_cuckoo_hash.c             |  47 +++++++--
 lib/hash/rte_hash.h                    |   8 +-
 4 files changed, 187 insertions(+), 9 deletions(-)

-- 
2.53.0