@@ -175,28 +175,25 @@ 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);
}
/**
This is a note to let you know that I have just added a patch titled batman-adv: Avoid recursive call_rcu for batadv_nc_node to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree which can be found at: http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue This patch is scheduled to be released in version 3.19.8-ckt14. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.19.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ---8<------------------------------------------------------------ From 732340399913930f260cd7b93936bc73a1bb3c7a Mon Sep 17 00:00:00 2001 From: Sven Eckelmann <sven@narfation.org> Date: Tue, 5 Jan 2016 12:06:19 +0100 Subject: batman-adv: Avoid recursive call_rcu for batadv_nc_node [ Upstream commit 44e8e7e91d6c7c7ab19688750f7257292640d1a0 ] 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> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- net/batman-adv/network-coding.c | 19 ++++++++----------- 1 file changed, 8 insertions(+), 11 deletions(-) -- 1.9.1