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>

diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index 604b4aa..12341ef 100644 (file)
--- 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);
 
                /*

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index 6d61d2f..3cf85d8 100644 (file)
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -1521,7 +1521,7 @@ static void ieee80211_set_disassoc(struct ieee80211_sub_if_data *sdata,
        memset(ifmgd->bssid, 0, ETH_ALEN);
 
        /* remove AP and TDLS peers */
-       sta_info_flush(sdata);
+       sta_info_flush_defer(sdata);
 
        /* finally reset all BSS / config parameters */
        changed |= ieee80211_reset_erp_info(sdata);

diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index d743645..7199b9d 100644 (file)
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -104,6 +104,16 @@ static void cleanup_single_sta(struct sta_info *sta)
         * neither mac80211 nor the driver can reference this
         * sta struct any more except by still existing timers
         * associated with this station that we clean up below.
+        *
+        * Note though that this still uses the sdata and even
+        * calls the driver in AP and mesh mode, so interfaces
+        * of those types mush use call sta_info_flush_cleanup()
+        * (typically via sta_info_flush()) before deconfiguring
+        * the driver.
+        *
+        * In station mode, nothing happens here so it doesn't
+        * have to (and doesn't) do that, this is intentional to
+        * speed up roaming.
         */
 
        if (test_sta_flag(sta, WLAN_STA_PS_STA)) {
@@ -887,14 +897,8 @@ void sta_info_stop(struct ieee80211_local *local)
        del_timer_sync(&local->sta_cleanup);
 }
 
-/**
- * sta_info_flush - flush matching STA entries from the STA table
- *
- * Returns the number of removed STA entries.
- *
- * @sdata: sdata to remove all stations from
- */
-int sta_info_flush(struct ieee80211_sub_if_data *sdata)
+
+int sta_info_flush_defer(struct ieee80211_sub_if_data *sdata)
 {
        struct ieee80211_local *local = sdata->local;
        struct sta_info *sta, *tmp;
@@ -911,12 +915,15 @@ int sta_info_flush(struct ieee80211_sub_if_data *sdata)
        }
        mutex_unlock(&local->sta_mtx);
 
+       return ret;
+}
+
+void sta_info_flush_cleanup(struct ieee80211_sub_if_data *sdata)
+{
        rcu_barrier();
 
        ieee80211_cleanup_sdata_stas(sdata);
        cancel_work_sync(&sdata->cleanup_stations_wk);
-
-       return ret;
 }
 
 void ieee80211_sta_expire(struct ieee80211_sub_if_data *sdata,

diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index 13698da..c3266ae 100644 (file)
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -548,7 +548,25 @@ 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(struct ieee80211_sub_if_data *sdata);
+int sta_info_flush_defer(struct ieee80211_sub_if_data *sdata);
+void sta_info_flush_cleanup(struct ieee80211_sub_if_data *sdata);
+
+/**
+ * sta_info_flush - flush matching STA entries from the STA table
+ *
+ * Returns the number of removed STA entries.
+ *
+ * @sdata: sdata to remove all stations from
+ */
+static inline int sta_info_flush(struct ieee80211_sub_if_data *sdata)
+{
+       int ret = sta_info_flush_defer(sdata);
+
+       sta_info_flush_cleanup(sdata);
+
+       return ret;
+}
+
 void sta_set_rate_info_tx(struct sta_info *sta,
                          const struct ieee80211_tx_rate *rate,
                          struct rate_info *rinfo);