On Thu, Sep 29, 2016 at 05:31:27PM +0200, Sven Eckelmann wrote:
On Dienstag, 20. September 2016 14:12:43 CEST Linus Lüssing wrote: [...]
/**
- batadv_hardif_neigh_get_pre - get the predecessor of a neighbor node
- @hard_iface: the interface this neighbour is connected to
- @neigh_addr: address of the neighbour to retrieve the predecessor for
- Tries to find the neighbor node which has an address closest to but
- smaller than the neigh_addr provided. In other words, tries to
- find a potential predecessor of a given MAC address.
- Return: The alphabetical predecessor of a neighbor node. Returns NULL
- if no such predecessor exists.
- */
+static struct batadv_hardif_neigh_node * +batadv_hardif_neigh_get_pre(struct batadv_hard_iface *hard_iface,
const u8 *neigh_addr)+{
- struct batadv_hardif_neigh_node *tmp_hardif_neigh, *hardif_neigh = NULL;
- rcu_read_lock();
- hlist_for_each_entry_rcu(tmp_hardif_neigh, &hard_iface->neigh_list,
list) {if (memcmp(tmp_hardif_neigh->addr, neigh_addr, ETH_ALEN) >= 0)break;if (!kref_get_unless_zero(&tmp_hardif_neigh->refcount))continue;if (hardif_neigh)batadv_hardif_neigh_put(hardif_neigh);hardif_neigh = tmp_hardif_neigh;- }
- rcu_read_unlock();
- return hardif_neigh;
+}
+/**
- batadv_hardif_neigh_create - create a hardif neighbour node
- @hard_iface: the interface this neighbour is connected to
- @neigh_addr: the interface address of the neighbour to retrieve
@@ -522,7 +559,7 @@ batadv_hardif_neigh_create(struct batadv_hard_iface *hard_iface, struct batadv_orig_node *orig_node) { struct batadv_priv *bat_priv = netdev_priv(hard_iface->soft_iface);
- struct batadv_hardif_neigh_node *hardif_neigh = NULL;
struct batadv_hardif_neigh_node *hardif_neigh = NULL, *pre_neigh;
spin_lock_bh(&hard_iface->neigh_list_lock);
@@ -547,7 +584,13 @@ batadv_hardif_neigh_create(struct batadv_hard_iface *hard_iface, if (bat_priv->algo_ops->neigh.hardif_init) bat_priv->algo_ops->neigh.hardif_init(hardif_neigh);
- hlist_add_head(&hardif_neigh->list, &hard_iface->neigh_list);
- pre_neigh = batadv_hardif_neigh_get_pre(hard_iface, neigh_addr);
- if (!pre_neigh) {
hlist_add_head(&hardif_neigh->list, &hard_iface->neigh_list);- } else {
hlist_add_behind(&hardif_neigh->list, &pre_neigh->list);batadv_hardif_neigh_put(pre_neigh);- }
I personally would have liked to see this in a separate patch. But there are more important things here.
First you have to use hlist_add_head_rcu and hlist_add_behind_rcu here because the readers use RCU to access the list. I think it would also be more appropriate to replace the rcu_read_lock in the batadv_hardif_neigh_get_pre function and instead use lockdep to mark the function as "requires hard_iface->neigh_list_lock".
PS: In v2, I haven't changed batadv_hardif_neigh_get_pre() to a non-rcu variant with lockdep. You are right, rcu isn't really necessary in this context, but I kind of like being able to have a function on one screen and seeing immediately whether it works or not, without needing to scroll.
And I liked keeping it similar to batadv_hardif_neigh_get().
Does that make sense?