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authorSven Eckelmann <sven@narfation.org>2016-01-05 14:06:19 +0300
committerAntonio Quartulli <a@unstable.cc>2016-01-16 17:48:41 +0300
commit44e8e7e91d6c7c7ab19688750f7257292640d1a0 (patch)
treef19e2bc2392e0a365ce434d684daf8a83ff4f786 /net/batman-adv
parent63b399272294e7a939cde41792dca38c549f0484 (diff)
downloadlinux-44e8e7e91d6c7c7ab19688750f7257292640d1a0.tar.xz
batman-adv: Avoid recursive call_rcu for batadv_nc_node
The batadv_nc_node_free_ref function uses call_rcu to delay the free of the batadv_nc_node object until no (already started) rcu_read_lock is enabled anymore. This makes sure that no context is still trying to access the object which should be removed. But batadv_nc_node also contains a reference to orig_node which must be removed. The reference drop of orig_node was done in the call_rcu function batadv_nc_node_free_rcu but should actually be done in the batadv_nc_node_release function to avoid nested call_rcus. This is important because rcu_barrier (e.g. batadv_softif_free or batadv_exit) will not detect the inner call_rcu as relevant for its execution. Otherwise this barrier will most likely be inserted in the queue before the callback of the first call_rcu was executed. The caller of rcu_barrier will therefore continue to run before the inner call_rcu callback finished. Fixes: d56b1705e28c ("batman-adv: network coding - detect coding nodes and remove these after timeout") Signed-off-by: Sven Eckelmann <sven@narfation.org> Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch> Signed-off-by: Antonio Quartulli <a@unstable.cc>
Diffstat (limited to 'net/batman-adv')
-rw-r--r--net/batman-adv/network-coding.c19
1 files changed, 8 insertions, 11 deletions
diff --git a/net/batman-adv/network-coding.c b/net/batman-adv/network-coding.c
index c98b0ab85449..cc63b44f0d2e 100644
--- a/net/batman-adv/network-coding.c
+++ b/net/batman-adv/network-coding.c
@@ -203,28 +203,25 @@ void batadv_nc_init_orig(struct batadv_orig_node *orig_node)
}
/**
- * batadv_nc_node_free_rcu - rcu callback to free an nc node and remove
- * its refcount on the orig_node
- * @rcu: rcu pointer of the nc node
+ * batadv_nc_node_release - release nc_node from lists and queue for free after
+ * rcu grace period
+ * @nc_node: the nc node to free
*/
-static void batadv_nc_node_free_rcu(struct rcu_head *rcu)
+static void batadv_nc_node_release(struct batadv_nc_node *nc_node)
{
- struct batadv_nc_node *nc_node;
-
- nc_node = container_of(rcu, struct batadv_nc_node, rcu);
batadv_orig_node_free_ref(nc_node->orig_node);
- kfree(nc_node);
+ kfree_rcu(nc_node, rcu);
}
/**
- * batadv_nc_node_free_ref - decrements the nc node refcounter and possibly
- * frees it
+ * batadv_nc_node_free_ref - decrement the nc node refcounter and possibly
+ * release it
* @nc_node: the nc node to free
*/
static void batadv_nc_node_free_ref(struct batadv_nc_node *nc_node)
{
if (atomic_dec_and_test(&nc_node->refcount))
- call_rcu(&nc_node->rcu, batadv_nc_node_free_rcu);
+ batadv_nc_node_release(nc_node);
}
/**