mac80211: AMPDU rx reorder timeout timer

This patch introduces a new timer, which will release
queued-up MPDUs from the reorder buffer, whenever
they've waited for more than HT_RX_REORDER_BUF_TIMEOUT
(which is at around 100 ms).

The advantage of having a dedicated timer, instead of
relying on a constant stream of freshly arriving aMPDUs
to release the old ones, is particularly observable when
even a small fraction of MPDUs are forever lost at
low network speeds.

Previously under these circumstances frames would become
stuck in the reorder buffer and the network stack of both
HT peers throttled back, instead of revving up and
gunning the pipes.

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/net/mac80211/agg-rx.c b/net/mac80211/agg-rx.c
index 965b272499fd..58eab9e8e4ee 100644
--- a/net/mac80211/agg-rx.c
+++ b/net/mac80211/agg-rx.c
@@ -86,6 +86,7 @@ void ___ieee80211_stop_rx_ba_session(struct sta_info *sta, u16 tid,
                                      tid, 0, reason);
 
         del_timer_sync(&tid_rx->session_timer);
+        del_timer_sync(&tid_rx->reorder_timer);
 
         call_rcu(&tid_rx->rcu_head, ieee80211_free_tid_rx);
 }
@@ -120,6 +121,20 @@ static void sta_rx_agg_session_timer_expired(unsigned long data)
         ieee80211_queue_work(&sta->local->hw, &sta->ampdu_mlme.work);
 }
 
+static void sta_rx_agg_reorder_timer_expired(unsigned long data)
+{
+        u8 *ptid = (u8 *)data;
+        u8 *timer_to_id = ptid - *ptid;
+        struct sta_info *sta = container_of(timer_to_id, struct sta_info,
+                        timer_to_tid[0]);
+
+        rcu_read_lock();
+        spin_lock(&sta->lock);
+        ieee80211_release_reorder_timeout(sta, *ptid);
+        spin_unlock(&sta->lock);
+        rcu_read_unlock();
+}
+
 static void ieee80211_send_addba_resp(struct ieee80211_sub_if_data *sdata, u8 *da, u16 tid,
                                       u8 dialog_token, u16 status, u16 policy,
                                       u16 buf_size, u16 timeout)
@@ -251,11 +266,18 @@ void ieee80211_process_addba_request(struct ieee80211_local *local,
                 goto end;
         }
 
+        spin_lock_init(&tid_agg_rx->reorder_lock);
+
         /* rx timer */
         tid_agg_rx->session_timer.function = sta_rx_agg_session_timer_expired;
         tid_agg_rx->session_timer.data = (unsigned long)&sta->timer_to_tid[tid];
         init_timer(&tid_agg_rx->session_timer);
 
+        /* rx reorder timer */
+        tid_agg_rx->reorder_timer.function = sta_rx_agg_reorder_timer_expired;
+        tid_agg_rx->reorder_timer.data = (unsigned long)&sta->timer_to_tid[tid];
+        init_timer(&tid_agg_rx->reorder_timer);
+
         /* prepare reordering buffer */
         tid_agg_rx->reorder_buf =
                 kcalloc(buf_size, sizeof(struct sk_buff *), GFP_ATOMIC);