From: Antonio Quartulli <a@unstable.cc>
To: davem@davemloft.net
Cc: netdev@vger.kernel.org, b.a.t.m.a.n@lists.open-mesh.org,
Antonio Quartulli <a@unstable.cc>,
Marek Lindner <mareklindner@neomailbox.ch>
Subject: [B.A.T.M.A.N.] [PATCH 2/8] batman-adv: Avoid recursive call_rcu for batadv_nc_node
Date: Sun, 17 Jan 2016 13:24:35 +0800 [thread overview]
Message-ID: <1453008281-15396-3-git-send-email-a@unstable.cc> (raw)
In-Reply-To: <1453008281-15396-1-git-send-email-a@unstable.cc>
From: Sven Eckelmann <sven@narfation.org>
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>
---
net/batman-adv/network-coding.c | 19 ++++++++-----------
1 file 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);
}
/**
--
2.7.0
next prev parent reply other threads:[~2016-01-17 5:24 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-17 5:24 [B.A.T.M.A.N.] pull request [net]: batman-adv 20160117 Antonio Quartulli
2016-01-17 5:24 ` [B.A.T.M.A.N.] [PATCH 1/8] batman-adv: Avoid recursive call_rcu for batadv_bla_claim Antonio Quartulli
2016-01-17 5:24 ` Antonio Quartulli [this message]
2016-01-17 5:24 ` [B.A.T.M.A.N.] [PATCH 3/8] batman-adv: Drop immediate batadv_orig_ifinfo free function Antonio Quartulli
2016-01-17 5:24 ` [B.A.T.M.A.N.] [PATCH 4/8] batman-adv: Drop immediate batadv_neigh_node " Antonio Quartulli
2016-01-17 5:24 ` [B.A.T.M.A.N.] [PATCH 5/8] batman-adv: Drop immediate batadv_hardif_neigh_node " Antonio Quartulli
2016-01-17 5:24 ` [B.A.T.M.A.N.] [PATCH 6/8] batman-adv: Drop immediate neigh_ifinfo " Antonio Quartulli
2016-01-17 5:24 ` [B.A.T.M.A.N.] [PATCH 7/8] batman-adv: Drop immediate batadv_hard_iface " Antonio Quartulli
2016-01-17 5:24 ` [B.A.T.M.A.N.] [PATCH 8/8] batman-adv: Drop immediate orig_node " Antonio Quartulli
2016-01-17 6:04 ` [B.A.T.M.A.N.] pull request [net]: batman-adv 20160117 David Miller
2016-01-17 6:12 ` Antonio Quartulli
2016-01-17 16:39 ` David Miller
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