mac80211: rework the pending packets code

The pending packets code is quite incomprehensible, uses memory barriers
nobody really understands, etc. This patch reworks it entirely, using
the queue spinlock, proper stop bits and the skb queues themselves to
indicate whether packets are pending or not (rather than a separate
variable like before).

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Reviewed-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 14 insertions, 8 deletions

diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 021166c8cce2..0247d8022f5f 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -365,16 +365,16 @@ static void __ieee80211_wake_queue(struct ieee80211_hw *hw, int queue,
 
         __clear_bit(reason, &local->queue_stop_reasons[queue]);
 
+        if (!skb_queue_empty(&local->pending[queue]) &&
+            local->queue_stop_reasons[queue] ==
+                                BIT(IEEE80211_QUEUE_STOP_REASON_PENDING))
+                tasklet_schedule(&local->tx_pending_tasklet);
+
         if (local->queue_stop_reasons[queue] != 0)
                 /* someone still has this queue stopped */
                 return;
 
-        if (test_bit(queue, local->queues_pending)) {
-                set_bit(queue, local->queues_pending_run);
-                tasklet_schedule(&local->tx_pending_tasklet);
-        } else {
-                netif_wake_subqueue(local->mdev, queue);
-        }
+        netif_wake_subqueue(local->mdev, queue);
 }
 
 void ieee80211_wake_queue_by_reason(struct ieee80211_hw *hw, int queue,
@@ -420,9 +420,15 @@ static void __ieee80211_stop_queue(struct ieee80211_hw *hw, int queue,
                 reason = IEEE80211_QUEUE_STOP_REASON_AGGREGATION;
         }
 
-        __set_bit(reason, &local->queue_stop_reasons[queue]);
+        /*
+         * Only stop if it was previously running, this is necessary
+         * for correct pending packets handling because there we may
+         * start (but not wake) the queue and rely on that.
+         */
+        if (!local->queue_stop_reasons[queue])
+                netif_stop_subqueue(local->mdev, queue);
 
-        netif_stop_subqueue(local->mdev, queue);
+        __set_bit(reason, &local->queue_stop_reasons[queue]);
 }
 
 void ieee80211_stop_queue_by_reason(struct ieee80211_hw *hw, int queue,