On Fri, 2011-08-26 at 17:18 -0700, Javier Cardona wrote:
> Signed-off-by: Javier Cardona <javier@xxxxxxxxxxx>
>
> ---
> v2: - Fix extra space (checkpatch)
> - Add lockdep check for RCU
> net/mac80211/mesh_pathtbl.c | 65 +++++++++++++++++-------------------------
> 1 files changed, 26 insertions(+), 39 deletions(-)
>
> diff --git a/net/mac80211/mesh_pathtbl.c b/net/mac80211/mesh_pathtbl.c
> index ea9e34a..3c03be9 100644
> --- a/net/mac80211/mesh_pathtbl.c
> +++ b/net/mac80211/mesh_pathtbl.c
> @@ -790,35 +790,6 @@ void mesh_plink_broken(struct sta_info *sta)
> rcu_read_unlock();
> }
>
> -/**
> - * mesh_path_flush_by_nexthop - Deletes mesh paths if their next hop matches
> - *
> - * @sta - mesh peer to match
> - *
> - * RCU notes: this function is called when a mesh plink transitions from
> - * PLINK_ESTAB to any other state, since PLINK_ESTAB state is the only one that
> - * allows path creation. This will happen before the sta can be freed (because
> - * sta_info_destroy() calls this) so any reader in a rcu read block will be
> - * protected against the plink disappearing.
> - */
> -void mesh_path_flush_by_nexthop(struct sta_info *sta)
> -{
> - struct mesh_table *tbl;
> - struct mesh_path *mpath;
> - struct mpath_node *node;
> - struct hlist_node *p;
> - int i;
> -
> - rcu_read_lock();
> - tbl = rcu_dereference(mesh_paths);
> - for_each_mesh_entry(tbl, p, node, i) {
> - mpath = node->mpath;
> - if (rcu_dereference(mpath->next_hop) == sta)
> - mesh_path_del(mpath->dst, mpath->sdata);
> - }
> - rcu_read_unlock();
> -}
> -
> static void mesh_path_node_reclaim(struct rcu_head *rp)
> {
> struct mpath_node *node = container_of(rp, struct mpath_node, rcu);
> @@ -845,7 +816,18 @@ static void __mesh_path_del(struct mesh_table *tbl, struct mpath_node *node)
> atomic_dec(&tbl->entries);
> }
>
> -static void mesh_path_flush(struct ieee80211_sub_if_data *sdata)
> +/**
> + * mesh_path_flush_by_nexthop - Deletes mesh paths if their next hop matches
> + *
> + * @sta - mesh peer to match
> + *
> + * RCU notes: this function is called when a mesh plink transitions from
> + * PLINK_ESTAB to any other state, since PLINK_ESTAB state is the only one that
> + * allows path creation. This will happen before the sta can be freed (because
> + * sta_info_destroy() calls this) so any reader in a rcu read block will be
> + * protected against the plink disappearing.
> + */
> +void mesh_path_flush_by_nexthop(struct sta_info *sta)
> {
> struct mesh_table *tbl;
> struct mesh_path *mpath;
> @@ -857,7 +839,7 @@ static void mesh_path_flush(struct ieee80211_sub_if_data *sdata)
> tbl = rcu_dereference(mesh_paths);
> for_each_mesh_entry(tbl, p, node, i) {
> mpath = node->mpath;
> - if (mpath->sdata == sdata) {
> + if (rcu_dereference(mpath->next_hop) == sta) {
> spin_lock_bh(&tbl->hashwlock[i]);
> __mesh_path_del(tbl, node);
> spin_unlock_bh(&tbl->hashwlock[i]);
> @@ -866,24 +848,23 @@ static void mesh_path_flush(struct ieee80211_sub_if_data *sdata)
> rcu_read_unlock();
> }
>
> -static void mpp_path_flush(struct ieee80211_sub_if_data *sdata)
> +static void table_flush_by_iface(struct mesh_table *tbl,
> + struct ieee80211_sub_if_data *sdata)
> {
> - struct mesh_table *tbl;
> struct mesh_path *mpath;
> struct mpath_node *node;
> struct hlist_node *p;
> int i;
>
> - read_lock_bh(&pathtbl_resize_lock);
> - tbl = rcu_dereference_protected(mpp_paths,
> - lockdep_is_held(pathtbl_resize_lock));
> + WARN_ON(!rcu_read_lock_held());
> for_each_mesh_entry(tbl, p, node, i) {
> mpath = node->mpath;
> + if (mpath->sdata != sdata)
> + continue;
> spin_lock_bh(&tbl->hashwlock[i]);
> __mesh_path_del(tbl, node);
> spin_unlock_bh(&tbl->hashwlock[i]);
> }
> - read_unlock_bh(&pathtbl_resize_lock);
> }
So what protects against the table being grown at the same time? A copy
will be made, but here you'll be iterating the old table -- which won't
crash or anything but is semantically incorrect.
johannes
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