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>

net/mac80211/ieee80211_i.h

@@ -184,10 +184,6 @@ struct ieee80211_rx_data {
 	u16 tkip_iv16;
 };
 
-struct ieee80211_tx_stored_packet {
-	struct sk_buff *skb;
-};
-
 struct beacon_data {
 	u8 *head, *tail;
 	int head_len, tail_len;
@@ -583,6 +579,7 @@ enum queue_stop_reason {
 	IEEE80211_QUEUE_STOP_REASON_CSA,
 	IEEE80211_QUEUE_STOP_REASON_AGGREGATION,
 	IEEE80211_QUEUE_STOP_REASON_SUSPEND,
+	IEEE80211_QUEUE_STOP_REASON_PENDING,
 };
 
 struct ieee80211_master_priv {
@@ -639,9 +636,7 @@ struct ieee80211_local {
 	struct sta_info *sta_hash[STA_HASH_SIZE];
 	struct timer_list sta_cleanup;
 
-	unsigned long queues_pending[BITS_TO_LONGS(IEEE80211_MAX_QUEUES)];
-	unsigned long queues_pending_run[BITS_TO_LONGS(IEEE80211_MAX_QUEUES)];
-	struct ieee80211_tx_stored_packet pending_packet[IEEE80211_MAX_QUEUES];
+	struct sk_buff_head pending[IEEE80211_MAX_QUEUES];
 	struct tasklet_struct tx_pending_tasklet;
 
 	/* number of interfaces with corresponding IFF_ flags */