mac80211: use call_rcu() on sta deletion

mac80211 calls synchronize_rcu() on sta deletion,
which increase the roaming time significantly.

Convert it into a call_rcu() mechanism, in order
to avoid blocking. Since some of the cleanup
functions might sleep, schedule from the call_rcu
callback a new work that will do the actual cleanup.

In order to make sure the cleanup occurs before
the interface went down, flush local->workqueue
on ieee80211_do_stop().

Signed-off-by: Yoni Divinsky <yoni.divinsky@ti.com>
Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index d747da5417471b220bb472ca95030e453cbe6f64..6f8a73c64fb31bde831609fa88a9b4e0425f02b9 100644 (file)
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -793,11 +793,20 @@ static void ieee80211_do_stop(struct ieee80211_sub_if_data *sdata,
                flush_work(&sdata->work);
                /*
                 * When we get here, the interface is marked down.
-                * Call synchronize_rcu() to wait for the RX path
+                * Call rcu_barrier() to wait both for the RX path
                 * should it be using the interface and enqueuing
-                * frames at this very time on another CPU.
+                * frames at this very time on another CPU, and
+                * for the sta free call_rcu callbacks.
                 */
-               synchronize_rcu();
+               rcu_barrier();
+
+               /*
+                * free_sta_rcu() enqueues a work for the actual
+                * sta cleanup, so we need to flush it while
+                * sdata is still valid.
+                */
+               flush_workqueue(local->workqueue);
+
                skb_queue_purge(&sdata->skb_queue);
 
                /*

diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index 06fa75ceb0251e6064d90661bf7b5e61f979b72c..9c8cd8b8f753134c1509b62ca39ce9d0e2469bfe 100644 (file)
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -91,6 +91,70 @@ static int sta_info_hash_del(struct ieee80211_local *local,
        return -ENOENT;
 }
 
+static void free_sta_work(struct work_struct *wk)
+{
+       struct sta_info *sta = container_of(wk, struct sta_info, free_sta_wk);
+       int ac, i;
+       struct tid_ampdu_tx *tid_tx;
+       struct ieee80211_sub_if_data *sdata = sta->sdata;
+       struct ieee80211_local *local = sdata->local;
+
+       /*
+        * At this point, when being called as call_rcu callback,
+        * 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.
+        */
+
+       if (test_sta_flag(sta, WLAN_STA_PS_STA)) {
+               BUG_ON(!sdata->bss);
+
+               clear_sta_flag(sta, WLAN_STA_PS_STA);
+
+               atomic_dec(&sdata->bss->num_sta_ps);
+               sta_info_recalc_tim(sta);
+       }
+
+       for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
+               local->total_ps_buffered -= skb_queue_len(&sta->ps_tx_buf[ac]);
+               __skb_queue_purge(&sta->ps_tx_buf[ac]);
+               __skb_queue_purge(&sta->tx_filtered[ac]);
+       }
+
+#ifdef CONFIG_MAC80211_MESH
+       if (ieee80211_vif_is_mesh(&sdata->vif)) {
+               mesh_accept_plinks_update(sdata);
+               mesh_plink_deactivate(sta);
+               del_timer_sync(&sta->plink_timer);
+       }
+#endif
+
+       cancel_work_sync(&sta->drv_unblock_wk);
+
+       /*
+        * Destroy aggregation state here. It would be nice to wait for the
+        * driver to finish aggregation stop and then clean up, but for now
+        * drivers have to handle aggregation stop being requested, followed
+        * directly by station destruction.
+        */
+       for (i = 0; i < STA_TID_NUM; i++) {
+               tid_tx = rcu_dereference_raw(sta->ampdu_mlme.tid_tx[i]);
+               if (!tid_tx)
+                       continue;
+               __skb_queue_purge(&tid_tx->pending);
+               kfree(tid_tx);
+       }
+
+       sta_info_free(local, sta);
+}
+
+static void free_sta_rcu(struct rcu_head *h)
+{
+       struct sta_info *sta = container_of(h, struct sta_info, rcu_head);
+
+       ieee80211_queue_work(&sta->local->hw, &sta->free_sta_wk);
+}
+
 /* protected by RCU */
 struct sta_info *sta_info_get(struct ieee80211_sub_if_data *sdata,
                              const u8 *addr)
@@ -241,6 +305,7 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
 
        spin_lock_init(&sta->lock);
        INIT_WORK(&sta->drv_unblock_wk, sta_unblock);
+       INIT_WORK(&sta->free_sta_wk, free_sta_work);
        INIT_WORK(&sta->ampdu_mlme.work, ieee80211_ba_session_work);
        mutex_init(&sta->ampdu_mlme.mtx);
 
@@ -654,8 +719,7 @@ int __must_check __sta_info_destroy(struct sta_info *sta)
 {
        struct ieee80211_local *local;
        struct ieee80211_sub_if_data *sdata;
-       int ret, i, ac;
-       struct tid_ampdu_tx *tid_tx;
+       int ret, i;
 
        might_sleep();
 
@@ -711,65 +775,14 @@ int __must_check __sta_info_destroy(struct sta_info *sta)
                WARN_ON_ONCE(ret != 0);
        }
 
-       /*
-        * At this point, after we wait for an RCU grace period,
-        * 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.
-        */
-       synchronize_rcu();
-
-       if (test_sta_flag(sta, WLAN_STA_PS_STA)) {
-               BUG_ON(!sdata->bss);
-
-               clear_sta_flag(sta, WLAN_STA_PS_STA);
-
-               atomic_dec(&sdata->bss->num_sta_ps);
-               sta_info_recalc_tim(sta);
-       }
-
-       for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
-               local->total_ps_buffered -= skb_queue_len(&sta->ps_tx_buf[ac]);
-               __skb_queue_purge(&sta->ps_tx_buf[ac]);
-               __skb_queue_purge(&sta->tx_filtered[ac]);
-       }
-
-#ifdef CONFIG_MAC80211_MESH
-       if (ieee80211_vif_is_mesh(&sdata->vif))
-               mesh_accept_plinks_update(sdata);
-#endif
-
        sta_dbg(sdata, "Removed STA %pM\n", sta->sta.addr);
 
-       cancel_work_sync(&sta->drv_unblock_wk);
-
        cfg80211_del_sta(sdata->dev, sta->sta.addr, GFP_KERNEL);
 
        rate_control_remove_sta_debugfs(sta);
        ieee80211_sta_debugfs_remove(sta);
 
-#ifdef CONFIG_MAC80211_MESH
-       if (ieee80211_vif_is_mesh(&sta->sdata->vif)) {
-               mesh_plink_deactivate(sta);
-               del_timer_sync(&sta->plink_timer);
-       }
-#endif
-
-       /*
-        * Destroy aggregation state here. It would be nice to wait for the
-        * driver to finish aggregation stop and then clean up, but for now
-        * drivers have to handle aggregation stop being requested, followed
-        * directly by station destruction.
-        */
-       for (i = 0; i < STA_TID_NUM; i++) {
-               tid_tx = rcu_dereference_raw(sta->ampdu_mlme.tid_tx[i]);
-               if (!tid_tx)
-                       continue;
-               __skb_queue_purge(&tid_tx->pending);
-               kfree(tid_tx);
-       }
-
-       sta_info_free(local, sta);
+       call_rcu(&sta->rcu_head, free_sta_rcu);
 
        return 0;
 }

diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index a470e1123a5576ed5e14b779ed4a9213cda407b7..c88f161f81185a678335fe3df6201fb8e64c8d80 100644 (file)
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -287,6 +287,7 @@ struct sta_ampdu_mlme {
 struct sta_info {
        /* General information, mostly static */
        struct list_head list;
+       struct rcu_head rcu_head;
        struct sta_info __rcu *hnext;
        struct ieee80211_local *local;
        struct ieee80211_sub_if_data *sdata;
@@ -297,6 +298,7 @@ struct sta_info {
        spinlock_t lock;
 
        struct work_struct drv_unblock_wk;
+       struct work_struct free_sta_wk;
 
        u16 listen_interval;