wifi: mac80211: Add non-atomic station iterator

[ Upstream commit 7c3b69e ]

Drivers may at times want to iterate their stations with a function
which requires some non-atomic operations.

ieee80211_iterate_stations_mtx() introduces an API to iterate stations
while holding that wiphy's mutex. This allows the iterating function to
do non-atomic operations safely.

Signed-off-by: Rory Little <rory@candelatech.com>
Link: https://patch.msgid.link/20240806004024.2014080-2-rory@candelatech.com
[unify internal list iteration functions]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Stable-dep-of: 8fac326 ("wifi: ath12k: fix atomic calls in ath12k_mac_op_set_bitrate_mask()")
Signed-off-by: Sasha Levin <sashal@kernel.org>

include/net/mac80211.h

@@ -6080,6 +6080,24 @@ void ieee80211_iterate_stations_atomic(struct ieee80211_hw *hw,
 				       void (*iterator)(void *data,
 						struct ieee80211_sta *sta),
 				       void *data);
+
+/**
+ * ieee80211_iterate_stations_mtx - iterate stations
+ *
+ * This function iterates over all stations associated with a given
+ * hardware that are currently uploaded to the driver and calls the callback
+ * function for them. This version can only be used while holding the wiphy
+ * mutex.
+ *
+ * @hw: the hardware struct of which the interfaces should be iterated over
+ * @iterator: the iterator function to call
+ * @data: first argument of the iterator function
+ */
+void ieee80211_iterate_stations_mtx(struct ieee80211_hw *hw,
+				    void (*iterator)(void *data,
+						     struct ieee80211_sta *sta),
+				    void *data);
+
 /**
  * ieee80211_queue_work - add work onto the mac80211 workqueue
  *

net/mac80211/util.c

@@ -827,7 +827,8 @@ static void __iterate_stations(struct ieee80211_local *local,
 {
 	struct sta_info *sta;
 
-	list_for_each_entry_rcu(sta, &local->sta_list, list) {
+	list_for_each_entry_rcu(sta, &local->sta_list, list,
+				lockdep_is_held(&local->hw.wiphy->mtx)) {
 		if (!sta->uploaded)
 			continue;
 
@@ -848,6 +849,19 @@ void ieee80211_iterate_stations_atomic(struct ieee80211_hw *hw,
 }
 EXPORT_SYMBOL_GPL(ieee80211_iterate_stations_atomic);
 
+void ieee80211_iterate_stations_mtx(struct ieee80211_hw *hw,
+				    void (*iterator)(void *data,
+						     struct ieee80211_sta *sta),
+				    void *data)
+{
+	struct ieee80211_local *local = hw_to_local(hw);
+
+	lockdep_assert_wiphy(local->hw.wiphy);
+
+	__iterate_stations(local, iterator, data);
+}
+EXPORT_SYMBOL_GPL(ieee80211_iterate_stations_mtx);
+
 struct ieee80211_vif *wdev_to_ieee80211_vif(struct wireless_dev *wdev)
 {
 	struct ieee80211_sub_if_data *sdata = IEEE80211_WDEV_TO_SUB_IF(wdev);