rcu_barrier() only waits for the currently scheduled rcu functions to finish - it won't wait for any function scheduled via another call_rcu() within an rcu scheduled function.
Unfortunately our batadv_tt_orig_list_entry_free_ref() does just that, via a batadv_orig_node_free_ref() call, leading to our rcu_barrier() call potentially missing such a batadv_orig_node_free_ref().
This patch fixes this issue by calling the batadv_orig_node_free_rcu() directly from the rcu callback, removing the unnecessary, additional call_rcu() layer here.
Signed-off-by: Linus Lüssing linus.luessing@web.de --- * v2: Added a code comment as discussed on IRC: To avoid forgetting about it, to avoid accidentally changing things back in the future.
originator.c | 2 +- originator.h | 1 + translation-table.c | 8 +++++++- 3 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/originator.c b/originator.c index 2f34525..1f01e93 100644 --- a/originator.c +++ b/originator.c @@ -117,7 +117,7 @@ out: return neigh_node; }
-static void batadv_orig_node_free_rcu(struct rcu_head *rcu) +void batadv_orig_node_free_rcu(struct rcu_head *rcu) { struct hlist_node *node_tmp; struct batadv_neigh_node *neigh_node, *tmp_neigh_node; diff --git a/originator.h b/originator.h index 7df48fa..4f9f88b 100644 --- a/originator.h +++ b/originator.h @@ -25,6 +25,7 @@ int batadv_originator_init(struct batadv_priv *bat_priv); void batadv_originator_free(struct batadv_priv *bat_priv); void batadv_purge_orig_ref(struct batadv_priv *bat_priv); +void batadv_orig_node_free_rcu(struct rcu_head *rcu); void batadv_orig_node_free_ref(struct batadv_orig_node *orig_node); struct batadv_orig_node *batadv_get_orig_node(struct batadv_priv *bat_priv, const uint8_t *addr); diff --git a/translation-table.c b/translation-table.c index 9322320..4fe07cf 100644 --- a/translation-table.c +++ b/translation-table.c @@ -144,7 +144,13 @@ static void batadv_tt_orig_list_entry_free_rcu(struct rcu_head *rcu) struct batadv_tt_orig_list_entry *orig_entry;
orig_entry = container_of(rcu, struct batadv_tt_orig_list_entry, rcu); - batadv_orig_node_free_ref(orig_entry->orig_node); + + /* We are in an rcu callback here, therefore we cannot use + * batadv_orig_node_free_ref() and its call_rcu(): + * An rcu_barrier() wouldn't wait for that to finish */ + if (atomic_dec_and_test(&orig_entry->orig_node->refcount)) + batadv_orig_node_free_rcu(&orig_entry->orig_node->rcu); + kfree(orig_entry); }