[B.A.T.M.A.N.] [PATCH 1/4] batman-adv: Correct rcu refcounting for gw_node

Sven Eckelmann
2011-01-30T01:52:56Z

<TODO: write a long monologue about every problem we have or could have or
maybe never had and would have when we not have it>

Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
batman-adv/gateway_client.c | 28 +++++++++++++---------------
batman-adv/types.h | 2 +-
2 files changed, 14 insertions(+), 16 deletions(-)

diff --git a/batman-adv/gateway_client.c b/batman-adv/gateway_client.c
index 429a013..8ce3a63 100644
--- a/batman-adv/gateway_client.c
+++ b/batman-adv/gateway_client.c
@@ -28,20 +28,18 @@
#include <linux/udp.h>
#include <linux/if_vlan.h>

-static void gw_node_free_ref(struct kref *refcount)
-{
- struct gw_node *gw_node;
-
- gw_node = container_of(refcount, struct gw_node, refcount);
- kfree(gw_node);
-}
-
static void gw_node_free_rcu(struct rcu_head *rcu)
{
struct gw_node *gw_node;

gw_node = container_of(rcu, struct gw_node, rcu);
- kref_put(&gw_node->refcount, gw_node_free_ref);
+ kfree(gw_node);
+}
+
+static void gw_node_free_ref(struct gw_node *gw_node)
+{
+ if (atomic_dec_and_test(&gw_node->refcount))
+ call_rcu(&gw_node->rcu, gw_node_free_rcu);
}

void *gw_get_selected(struct bat_priv *bat_priv)
@@ -61,7 +59,7 @@ void gw_deselect(struct bat_priv *bat_priv)
bat_priv->curr_gw = NULL;

if (gw_node)
- kref_put(&gw_node->refcount, gw_node_free_ref);
+ gw_node_free_ref(gw_node);
}

static struct gw_node *gw_select(struct bat_priv *bat_priv,
@@ -69,8 +67,8 @@ static struct gw_node *gw_select(struct bat_priv *bat_priv,
{
struct gw_node *curr_gw_node = bat_priv->curr_gw;

- if (new_gw_node)
- kref_get(&new_gw_node->refcount);
+ if (new_gw_node && !atomic_inc_not_zero(&new_gw_node->refcount))
+ return NULL;

bat_priv->curr_gw = new_gw_node;
return curr_gw_node;
@@ -181,7 +179,7 @@ void gw_election(struct bat_priv *bat_priv)

/* the kfree() has to be outside of the rcu lock */
if (old_gw_node)
- kref_put(&old_gw_node->refcount, gw_node_free_ref);
+ gw_node_free_ref(old_gw_node);
}

void gw_check_election(struct bat_priv *bat_priv, struct orig_node *orig_node)
@@ -242,7 +240,7 @@ static void gw_node_add(struct bat_priv *bat_priv,
memset(gw_node, 0, sizeof(struct gw_node));
INIT_HLIST_NODE(&gw_node->list);
gw_node->orig_node = orig_node;
- kref_init(&gw_node->refcount);
+ atomic_set(&gw_node->refcount, 1);

spin_lock_bh(&bat_priv->gw_list_lock);
hlist_add_head_rcu(&gw_node->list, &bat_priv->gw_list);
@@ -325,7 +323,7 @@ void gw_node_purge(struct bat_priv *bat_priv)
gw_deselect(bat_priv);

hlist_del_rcu(&gw_node->list);
- call_rcu(&gw_node->rcu, gw_node_free_rcu);
+ gw_node_free_ref(gw_node);
}

diff --git a/batman-adv/types.h b/batman-adv/types.h
index e4a0462..ca5f20a 100644
--- a/batman-adv/types.h
+++ b/batman-adv/types.h
@@ -100,7 +100,7 @@ struct gw_node {
struct hlist_node list;
struct orig_node *orig_node;
unsigned long deleted;
- struct kref refcount;
+ atomic_t refcount;
struct rcu_head rcu;
};

--
1.7.2.3