mac80211: optimise roaming time again

The last fixes re-added the RCU synchronize penalty
on roaming to fix the races. Split up sta_info_flush()
now to get rid of that again, and let managed mode
(and only it) delay the actual destruction.

Tested-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 10 insertions, 5 deletions

diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index 604b4aae3364..12341efb109e 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -775,8 +775,10 @@ static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata,
          * This is relevant only in WDS mode, in all other modes we've
          * already removed all stations when disconnecting or similar,
          * so warn otherwise.
+         *
+         * We call sta_info_flush_cleanup() later, to combine RCU waits.
          */
-        flushed = sta_info_flush(sdata);
+        flushed = sta_info_flush_defer(sdata);
         WARN_ON_ONCE((sdata->vif.type != NL80211_IFTYPE_WDS && flushed > 0) ||
                      (sdata->vif.type == NL80211_IFTYPE_WDS && flushed != 1));
 
@@ -861,11 +863,14 @@ static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata,
                 cancel_work_sync(&sdata->work);
                 /*
                  * When we get here, the interface is marked down.
-                 * Call synchronize_rcu() to wait for the RX path
-                 * should it be using the interface and enqueuing
-                 * frames at this very time on another CPU.
+                 * sta_info_flush_cleanup() calls rcu_barrier to
+                 * wait for the station call_rcu() calls to complete,
+                 * here we require it to wait for the RX path in case
+                 * it is using the interface and enqueuing frames at
+                 * this very time on another CPU.
                  */
-                synchronize_rcu();
+                sta_info_flush_cleanup(sdata);
+
                 skb_queue_purge(&sdata->skb_queue);
 
                 /*