[linux-next] LinuxNextTracking branch, master, updated. next-20130520

batman at open-mesh.org batman at open-mesh.org
Tue May 21 00:17:25 CEST 2013


The following commit has been merged in the master branch:
commit 72822225bd41320a98f5d7cde38317766e18983f
Author: Linus Lüssing <linus.luessing at web.de>
Date:   Mon Apr 15 21:43:29 2013 +0800

    batman-adv: Fix rcu_barrier() miss due to double call_rcu() in TT code
    
    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 at web.de>
    Signed-off-by: Marek Lindner <lindner_marek at yahoo.de>
    Acked-by: Antonio Quartulli <ordex at autistici.org>

diff --git a/net/batman-adv/originator.c b/net/batman-adv/originator.c
index 2f34525..fad1a20 100644
--- a/net/batman-adv/originator.c
+++ b/net/batman-adv/originator.c
@@ -156,12 +156,28 @@ static void batadv_orig_node_free_rcu(struct rcu_head *rcu)
 	kfree(orig_node);
 }
 
+/**
+ * batadv_orig_node_free_ref - decrement the orig node refcounter and possibly
+ * schedule an rcu callback for freeing it
+ * @orig_node: the orig node to free
+ */
 void batadv_orig_node_free_ref(struct batadv_orig_node *orig_node)
 {
 	if (atomic_dec_and_test(&orig_node->refcount))
 		call_rcu(&orig_node->rcu, batadv_orig_node_free_rcu);
 }
 
+/**
+ * batadv_orig_node_free_ref_now - decrement the orig node refcounter and
+ * possibly free it (without rcu callback)
+ * @orig_node: the orig node to free
+ */
+void batadv_orig_node_free_ref_now(struct batadv_orig_node *orig_node)
+{
+	if (atomic_dec_and_test(&orig_node->refcount))
+		batadv_orig_node_free_rcu(&orig_node->rcu);
+}
+
 void batadv_originator_free(struct batadv_priv *bat_priv)
 {
 	struct batadv_hashtable *hash = bat_priv->orig_hash;
diff --git a/net/batman-adv/originator.h b/net/batman-adv/originator.h
index 7df48fa..734e5a3 100644
--- a/net/batman-adv/originator.h
+++ b/net/batman-adv/originator.h
@@ -26,6 +26,7 @@ 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_ref(struct batadv_orig_node *orig_node);
+void batadv_orig_node_free_ref_now(struct batadv_orig_node *orig_node);
 struct batadv_orig_node *batadv_get_orig_node(struct batadv_priv *bat_priv,
 					      const uint8_t *addr);
 struct batadv_neigh_node *
diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c
index 5e89dee..9e87485 100644
--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -144,7 +144,12 @@ 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
+	 */
+	batadv_orig_node_free_ref_now(orig_entry->orig_node);
 	kfree(orig_entry);
 }
 

-- 
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