mac80211: optimise AP stop RCU handling

If there are VLANs, stopping an AP is inefficient as it
calls rcu_barrier() once for each interface (the VLANs
and the AP itself). Optimise this by moving rcu_barrier()
out of the station cleanups and calling it only once for
all interfaces combined.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index c3266aed4a07..031e4a5bbeca 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -549,6 +549,19 @@ void sta_info_recalc_tim(struct sta_info *sta);
 void sta_info_init(struct ieee80211_local *local);
 void sta_info_stop(struct ieee80211_local *local);
 int sta_info_flush_defer(struct ieee80211_sub_if_data *sdata);
+
+/**
+ * sta_info_flush_cleanup - flush the sta_info cleanup queue
+ * @sdata: the interface
+ *
+ * Flushes the sta_info cleanup queue for a given interface;
+ * this is necessary before the interface is removed or, for
+ * AP/mesh interfaces, before it is deconfigured.
+ *
+ * Note an rcu_barrier() must precede the function, after all
+ * stations have been flushed/removed to ensure the call_rcu()
+ * calls that add stations to the cleanup queue have completed.
+ */
 void sta_info_flush_cleanup(struct ieee80211_sub_if_data *sdata);
 
 /**
@@ -562,6 +575,7 @@ static inline int sta_info_flush(struct ieee80211_sub_if_data *sdata)
 {
         int ret = sta_info_flush_defer(sdata);
 
+        rcu_barrier();
         sta_info_flush_cleanup(sdata);
 
         return ret;