mac80211: make ieee80211_iterate_active_interfaces not need rtnl

Interface iteration in mac80211 can be done without holding any
locks because I converted it to RCU. Initially, I thought this
wouldn't be needed for ieee80211_iterate_active_interfaces but
it's turning out that multi-BSS AP support can be much simpler
in a driver if ieee80211_iterate_active_interfaces can be called
without holding locks. This converts it to use RCU, it adds a
requirement that the callback it invokes cannot sleep.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 3 deletions

diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 5227c16f113e..7b278e9aa1a4 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -482,10 +482,9 @@ void ieee80211_iterate_active_interfaces(struct ieee80211_hw *hw,
         struct ieee80211_local *local = hw_to_local(hw);
         struct ieee80211_sub_if_data *sdata;
 
-        ASSERT_RTNL();
+        rcu_read_lock();
 
-        /* we hold the RTNL here so can safely walk the list */
-        list_for_each_entry(sdata, &local->interfaces, list) {
+        list_for_each_entry_rcu(sdata, &local->interfaces, list) {
                 switch (sdata->type) {
                 case IEEE80211_IF_TYPE_INVALID:
                 case IEEE80211_IF_TYPE_MNTR:
@@ -503,5 +502,7 @@ void ieee80211_iterate_active_interfaces(struct ieee80211_hw *hw,
                         iterator(data, sdata->dev->dev_addr,
                                  sdata->dev->ifindex);
         }
+
+        rcu_read_unlock();
 }
 EXPORT_SYMBOL_GPL(ieee80211_iterate_active_interfaces);