mac80211: serialize rx path workers

This patch addresses the issue of serialization between
the main rx path and various reorder release timers.

<http://www.spinics.net/lists/linux-wireless/msg57214.html>

It converts the previously local "frames" queue into
a global rx queue [rx_skb_queue]. This way, everyone
(be it the main rx-path or some reorder release timeout)
can add frames to it.

Only one active rx handler worker [ieee80211_rx_handlers]
is needed. All other threads which have lost the race of
"runnning_rx_handler" can now simply "return", knowing that
the thread who had the "edge" will also take care of their
workload.

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

1 files changed, 37 insertions, 43 deletions

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 260b48bac42e..12cbb4df81aa 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -533,9 +533,9 @@ static inline u16 seq_sub(u16 sq1, u16 sq2)
 
 static void ieee80211_release_reorder_frame(struct ieee80211_hw *hw,
                                             struct tid_ampdu_rx *tid_agg_rx,
-                                            int index,
-                                            struct sk_buff_head *frames)
+                                            int index)
 {
+        struct ieee80211_local *local = hw_to_local(hw);
         struct sk_buff *skb = tid_agg_rx->reorder_buf[index];
         struct ieee80211_rx_status *status;
 
@@ -549,7 +549,7 @@ static void ieee80211_release_reorder_frame(struct ieee80211_hw *hw,
         tid_agg_rx->reorder_buf[index] = NULL;
         status = IEEE80211_SKB_RXCB(skb);
         status->rx_flags |= IEEE80211_RX_DEFERRED_RELEASE;
-        __skb_queue_tail(frames, skb);
+        skb_queue_tail(&local->rx_skb_queue, skb);
 
 no_frame:
         tid_agg_rx->head_seq_num = seq_inc(tid_agg_rx->head_seq_num);
@@ -557,8 +557,7 @@ no_frame:
 
 static void ieee80211_release_reorder_frames(struct ieee80211_hw *hw,
                                              struct tid_ampdu_rx *tid_agg_rx,
-                                             u16 head_seq_num,
-                                             struct sk_buff_head *frames)
+                                             u16 head_seq_num)
 {
         int index;
 
@@ -567,7 +566,7 @@ static void ieee80211_release_reorder_frames(struct ieee80211_hw *hw,
         while (seq_less(tid_agg_rx->head_seq_num, head_seq_num)) {
                 index = seq_sub(tid_agg_rx->head_seq_num, tid_agg_rx->ssn) %
                                                         tid_agg_rx->buf_size;
-                ieee80211_release_reorder_frame(hw, tid_agg_rx, index, frames);
+                ieee80211_release_reorder_frame(hw, tid_agg_rx, index);
         }
 }
 
@@ -583,8 +582,7 @@ static void ieee80211_release_reorder_frames(struct ieee80211_hw *hw,
 #define HT_RX_REORDER_BUF_TIMEOUT (HZ / 10)
 
 static void ieee80211_sta_reorder_release(struct ieee80211_hw *hw,
-                                          struct tid_ampdu_rx *tid_agg_rx,
-                                          struct sk_buff_head *frames)
+                                          struct tid_ampdu_rx *tid_agg_rx)
 {
         int index, j;
 
@@ -615,8 +613,7 @@ static void ieee80211_sta_reorder_release(struct ieee80211_hw *hw,
                                 wiphy_debug(hw->wiphy,
                                             "release an RX reorder frame due to timeout on earlier frames\n");
 #endif
-                        ieee80211_release_reorder_frame(hw, tid_agg_rx,
-                                                        j, frames);
+                        ieee80211_release_reorder_frame(hw, tid_agg_rx, j);
 
                         /*
                          * Increment the head seq# also for the skipped slots.
@@ -626,7 +623,7 @@ static void ieee80211_sta_reorder_release(struct ieee80211_hw *hw,
                         skipped = 0;
                 }
         } else while (tid_agg_rx->reorder_buf[index]) {
-                ieee80211_release_reorder_frame(hw, tid_agg_rx, index, frames);
+                ieee80211_release_reorder_frame(hw, tid_agg_rx, index);
                 index = seq_sub(tid_agg_rx->head_seq_num, tid_agg_rx->ssn) %
                                                         tid_agg_rx->buf_size;
         }
@@ -682,8 +679,7 @@ set_release_timer:
  */
 static bool ieee80211_sta_manage_reorder_buf(struct ieee80211_hw *hw,
                                              struct tid_ampdu_rx *tid_agg_rx,
-                                             struct sk_buff *skb,
-                                             struct sk_buff_head *frames)
+                                             struct sk_buff *skb)
 {
         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
         u16 sc = le16_to_cpu(hdr->seq_ctrl);
@@ -710,8 +706,7 @@ static bool ieee80211_sta_manage_reorder_buf(struct ieee80211_hw *hw,
         if (!seq_less(mpdu_seq_num, head_seq_num + buf_size)) {
                 head_seq_num = seq_inc(seq_sub(mpdu_seq_num, buf_size));
                 /* release stored frames up to new head to stack */
-                ieee80211_release_reorder_frames(hw, tid_agg_rx, head_seq_num,
-                                                 frames);
+                ieee80211_release_reorder_frames(hw, tid_agg_rx, head_seq_num);
         }
 
         /* Now the new frame is always in the range of the reordering buffer */
@@ -739,7 +734,7 @@ static bool ieee80211_sta_manage_reorder_buf(struct ieee80211_hw *hw,
         tid_agg_rx->reorder_buf[index] = skb;
         tid_agg_rx->reorder_time[index] = jiffies;
         tid_agg_rx->stored_mpdu_num++;
-        ieee80211_sta_reorder_release(hw, tid_agg_rx, frames);
+        ieee80211_sta_reorder_release(hw, tid_agg_rx);
 
  out:
         spin_unlock(&tid_agg_rx->reorder_lock);
@@ -750,8 +745,7 @@ static bool ieee80211_sta_manage_reorder_buf(struct ieee80211_hw *hw,
  * Reorder MPDUs from A-MPDUs, keeping them on a buffer. Returns
  * true if the MPDU was buffered, false if it should be processed.
  */
-static void ieee80211_rx_reorder_ampdu(struct ieee80211_rx_data *rx,
-                                       struct sk_buff_head *frames)
+static void ieee80211_rx_reorder_ampdu(struct ieee80211_rx_data *rx)
 {
         struct sk_buff *skb = rx->skb;
         struct ieee80211_local *local = rx->local;
@@ -806,11 +800,11 @@ static void ieee80211_rx_reorder_ampdu(struct ieee80211_rx_data *rx,
          * sure that we cannot get to it any more before doing
          * anything with it.
          */
-        if (ieee80211_sta_manage_reorder_buf(hw, tid_agg_rx, skb, frames))
+        if (ieee80211_sta_manage_reorder_buf(hw, tid_agg_rx, skb))
                 return;
 
  dont_reorder:
-        __skb_queue_tail(frames, skb);
+        skb_queue_tail(&local->rx_skb_queue, skb);
 }
 
 static ieee80211_rx_result debug_noinline
@@ -1931,7 +1925,7 @@ ieee80211_rx_h_data(struct ieee80211_rx_data *rx)
 }
 
 static ieee80211_rx_result debug_noinline
-ieee80211_rx_h_ctrl(struct ieee80211_rx_data *rx, struct sk_buff_head *frames)
+ieee80211_rx_h_ctrl(struct ieee80211_rx_data *rx)
 {
         struct ieee80211_local *local = rx->local;
         struct ieee80211_hw *hw = &local->hw;
@@ -1971,8 +1965,7 @@ ieee80211_rx_h_ctrl(struct ieee80211_rx_data *rx, struct sk_buff_head *frames)
 
                 spin_lock(&tid_agg_rx->reorder_lock);
                 /* release stored frames up to start of BAR */
-                ieee80211_release_reorder_frames(hw, tid_agg_rx, start_seq_num,
-                                                 frames);
+                ieee80211_release_reorder_frames(hw, tid_agg_rx, start_seq_num);
                 spin_unlock(&tid_agg_rx->reorder_lock);
 
                 kfree_skb(skb);
@@ -2489,8 +2482,7 @@ static void ieee80211_rx_handlers_result(struct ieee80211_rx_data *rx,
         }
 }
 
-static void ieee80211_rx_handlers(struct ieee80211_rx_data *rx,
-                                  struct sk_buff_head *frames)
+static void ieee80211_rx_handlers(struct ieee80211_rx_data *rx)
 {
         ieee80211_rx_result res = RX_DROP_MONITOR;
         struct sk_buff *skb;
@@ -2502,7 +2494,15 @@ static void ieee80211_rx_handlers(struct ieee80211_rx_data *rx,
                         goto rxh_next;  \
         } while (0);
 
-        while ((skb = __skb_dequeue(frames))) {
+        spin_lock(&rx->local->rx_skb_queue.lock);
+        if (rx->local->running_rx_handler)
+                goto unlock;
+
+        rx->local->running_rx_handler = true;
+
+        while ((skb = __skb_dequeue(&rx->local->rx_skb_queue))) {
+                spin_unlock(&rx->local->rx_skb_queue.lock);
+
                 /*
                  * all the other fields are valid across frames
                  * that belong to an aMPDU since they are on the
@@ -2525,12 +2525,7 @@ static void ieee80211_rx_handlers(struct ieee80211_rx_data *rx,
                         CALL_RXH(ieee80211_rx_h_mesh_fwding);
 #endif
                 CALL_RXH(ieee80211_rx_h_data)
-
-                /* special treatment -- needs the queue */
-                res = ieee80211_rx_h_ctrl(rx, frames);
-                if (res != RX_CONTINUE)
-                        goto rxh_next;
-
+                CALL_RXH(ieee80211_rx_h_ctrl);
                 CALL_RXH(ieee80211_rx_h_mgmt_check)
                 CALL_RXH(ieee80211_rx_h_action)
                 CALL_RXH(ieee80211_rx_h_userspace_mgmt)
@@ -2539,18 +2534,20 @@ static void ieee80211_rx_handlers(struct ieee80211_rx_data *rx,
 
  rxh_next:
                 ieee80211_rx_handlers_result(rx, res);
-
+                spin_lock(&rx->local->rx_skb_queue.lock);
 #undef CALL_RXH
         }
+
+        rx->local->running_rx_handler = false;
+
+ unlock:
+        spin_unlock(&rx->local->rx_skb_queue.lock);
 }
 
 static void ieee80211_invoke_rx_handlers(struct ieee80211_rx_data *rx)
 {
-        struct sk_buff_head reorder_release;
         ieee80211_rx_result res = RX_DROP_MONITOR;
 
-        __skb_queue_head_init(&reorder_release);
-
 #define CALL_RXH(rxh)                   \
         do {                            \
                 res = rxh(rx);          \
@@ -2561,9 +2558,9 @@ static void ieee80211_invoke_rx_handlers(struct ieee80211_rx_data *rx)
         CALL_RXH(ieee80211_rx_h_passive_scan)
         CALL_RXH(ieee80211_rx_h_check)
 
-        ieee80211_rx_reorder_ampdu(rx, &reorder_release);
+        ieee80211_rx_reorder_ampdu(rx);
 
-        ieee80211_rx_handlers(rx, &reorder_release);
+        ieee80211_rx_handlers(rx);
         return;
 
  rxh_next:
@@ -2578,7 +2575,6 @@ static void ieee80211_invoke_rx_handlers(struct ieee80211_rx_data *rx)
  */
 void ieee80211_release_reorder_timeout(struct sta_info *sta, int tid)
 {
-        struct sk_buff_head frames;
         struct ieee80211_rx_data rx = {
                 .sta = sta,
                 .sdata = sta->sdata,
@@ -2591,13 +2587,11 @@ void ieee80211_release_reorder_timeout(struct sta_info *sta, int tid)
         if (!tid_agg_rx)
                 return;
 
-        __skb_queue_head_init(&frames);
-
         spin_lock(&tid_agg_rx->reorder_lock);
-        ieee80211_sta_reorder_release(&sta->local->hw, tid_agg_rx, &frames);
+        ieee80211_sta_reorder_release(&sta->local->hw, tid_agg_rx);
         spin_unlock(&tid_agg_rx->reorder_lock);
 
-        ieee80211_rx_handlers(&rx, &frames);
+        ieee80211_rx_handlers(&rx);
 }
 
 /* main receive path */