mac80211: fix aggregation to not require queue stop

Instead of stopping the entire AC queue when enabling aggregation
(which was only done for hardware with aggregation queues) buffer
the packets for each station, and release them to the pending skb
queue once aggregation is turned on successfully.

We get a little more code, but it becomes conceptually simpler and
we can remove the entire virtual queue mechanism from mac80211 in
a follow-up patch.

This changes how mac80211 behaves towards drivers that support
aggregation but have no hardware queues -- those drivers will now
not be handed packets while the aggregation session is being
established, but only after it has been fully established.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 116 insertions, 26 deletions

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index a0e00c6339ca..906ab785db40 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -984,9 +984,9 @@ __ieee80211_tx_prepare(struct ieee80211_tx_data *tx,
 	struct ieee80211_hdr *hdr;
 	struct ieee80211_sub_if_data *sdata;
 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
-
 	int hdrlen, tid;
 	u8 *qc, *state;
+	bool queued = false;
 
 	memset(tx, 0, sizeof(*tx));
 	tx->skb = skb;
@@ -1013,20 +1013,53 @@ __ieee80211_tx_prepare(struct ieee80211_tx_data *tx,
 		 */
 	}
 
+	/*
+	 * If this flag is set to true anywhere, and we get here,
+	 * we are doing the needed processing, so remove the flag
+	 * now.
+	 */
+	info->flags &= ~IEEE80211_TX_INTFL_NEED_TXPROCESSING;
+
 	hdr = (struct ieee80211_hdr *) skb->data;
 
 	tx->sta = sta_info_get(local, hdr->addr1);
 
-	if (tx->sta && ieee80211_is_data_qos(hdr->frame_control)) {
+	if (tx->sta && ieee80211_is_data_qos(hdr->frame_control) &&
+	    (local->hw.flags & IEEE80211_HW_AMPDU_AGGREGATION)) {
 		unsigned long flags;
+		struct tid_ampdu_tx *tid_tx;
+
 		qc = ieee80211_get_qos_ctl(hdr);
 		tid = *qc & IEEE80211_QOS_CTL_TID_MASK;
 
 		spin_lock_irqsave(&tx->sta->lock, flags);
+		/*
+		 * XXX: This spinlock could be fairly expensive, but see the
+		 *	comment in agg-tx.c:ieee80211_agg_tx_operational().
+		 *	One way to solve this would be to do something RCU-like
+		 *	for managing the tid_tx struct and using atomic bitops
+		 *	for the actual state -- by introducing an actual
+		 *	'operational' bit that would be possible. It would
+		 *	require changing ieee80211_agg_tx_operational() to
+		 *	set that bit, and changing the way tid_tx is managed
+		 *	everywhere, including races between that bit and
+		 *	tid_tx going away (tid_tx being added can be easily
+		 *	committed to memory before the 'operational' bit).
+		 */
+		tid_tx = tx->sta->ampdu_mlme.tid_tx[tid];
 		state = &tx->sta->ampdu_mlme.tid_state_tx[tid];
-		if (*state == HT_AGG_STATE_OPERATIONAL)
+		if (*state == HT_AGG_STATE_OPERATIONAL) {
 			info->flags |= IEEE80211_TX_CTL_AMPDU;
+		} else if (*state != HT_AGG_STATE_IDLE) {
+			/* in progress */
+			queued = true;
+			info->flags |= IEEE80211_TX_INTFL_NEED_TXPROCESSING;
+			__skb_queue_tail(&tid_tx->pending, skb);
+		}
 		spin_unlock_irqrestore(&tx->sta->lock, flags);
+
+		if (unlikely(queued))
+			return TX_QUEUED;
 	}
 
 	if (is_multicast_ether_addr(hdr->addr1)) {
@@ -1077,7 +1110,14 @@ static int ieee80211_tx_prepare(struct ieee80211_local *local,
 	}
 	if (unlikely(!dev))
 		return -ENODEV;
-	/* initialises tx with control */
+	/*
+	 * initialises tx with control
+	 *
+	 * return value is safe to ignore here because this function
+	 * can only be invoked for multicast frames
+	 *
+	 * XXX: clean up
+	 */
 	__ieee80211_tx_prepare(tx, skb, dev);
 	dev_put(dev);
 	return 0;
@@ -1188,7 +1228,8 @@ static int invoke_tx_handlers(struct ieee80211_tx_data *tx)
 	return 0;
 }
 
-static int ieee80211_tx(struct net_device *dev, struct sk_buff *skb)
+static void ieee80211_tx(struct net_device *dev, struct sk_buff *skb,
+			 bool txpending)
 {
 	struct ieee80211_local *local = wdev_priv(dev->ieee80211_ptr);
 	struct sta_info *sta;
@@ -1202,11 +1243,11 @@ static int ieee80211_tx(struct net_device *dev, struct sk_buff *skb)
 
 	queue = skb_get_queue_mapping(skb);
 
-	WARN_ON(!skb_queue_empty(&local->pending[queue]));
+	WARN_ON(!txpending && !skb_queue_empty(&local->pending[queue]));
 
 	if (unlikely(skb->len < 10)) {
 		dev_kfree_skb(skb);
-		return 0;
+		return;
 	}
 
 	rcu_read_lock();
@@ -1214,10 +1255,13 @@ static int ieee80211_tx(struct net_device *dev, struct sk_buff *skb)
 	/* initialises tx */
 	res_prepare = __ieee80211_tx_prepare(&tx, skb, dev);
 
-	if (res_prepare == TX_DROP) {
+	if (unlikely(res_prepare == TX_DROP)) {
 		dev_kfree_skb(skb);
 		rcu_read_unlock();
-		return 0;
+		return;
+	} else if (unlikely(res_prepare == TX_QUEUED)) {
+		rcu_read_unlock();
+		return;
 	}
 
 	sta = tx.sta;
@@ -1251,7 +1295,12 @@ static int ieee80211_tx(struct net_device *dev, struct sk_buff *skb)
 			do {
 				next = skb->next;
 				skb->next = NULL;
-				skb_queue_tail(&local->pending[queue], skb);
+				if (unlikely(txpending))
+					skb_queue_head(&local->pending[queue],
+						       skb);
+				else
+					skb_queue_tail(&local->pending[queue],
+						       skb);
 			} while ((skb = next));
 
 			/*
@@ -1276,7 +1325,7 @@ static int ieee80211_tx(struct net_device *dev, struct sk_buff *skb)
 	}
  out:
 	rcu_read_unlock();
-	return 0;
+	return;
 
  drop:
 	rcu_read_unlock();
@@ -1287,7 +1336,6 @@ static int ieee80211_tx(struct net_device *dev, struct sk_buff *skb)
 		dev_kfree_skb(skb);
 		skb = next;
 	}
-	return 0;
 }
 
 /* device xmit handlers */
@@ -1346,7 +1394,6 @@ int ieee80211_master_start_xmit(struct sk_buff *skb, struct net_device *dev)
 		FOUND_SDATA,
 		UNKNOWN_ADDRESS,
 	} monitor_iface = NOT_MONITOR;
-	int ret;
 
 	if (skb->iif)
 		odev = dev_get_by_index(&init_net, skb->iif);
@@ -1360,7 +1407,7 @@ int ieee80211_master_start_xmit(struct sk_buff *skb, struct net_device *dev)
 		       "originating device\n", dev->name);
 #endif
 		dev_kfree_skb(skb);
-		return 0;
+		return NETDEV_TX_OK;
 	}
 
 	if ((local->hw.flags & IEEE80211_HW_PS_NULLFUNC_STACK) &&
@@ -1389,7 +1436,7 @@ int ieee80211_master_start_xmit(struct sk_buff *skb, struct net_device *dev)
 		else
 			if (mesh_nexthop_lookup(skb, osdata)) {
 				dev_put(odev);
-				return 0;
+				return NETDEV_TX_OK;
 			}
 		if (memcmp(odev->dev_addr, hdr->addr4, ETH_ALEN) != 0)
 			IEEE80211_IFSTA_MESH_CTR_INC(&osdata->u.mesh,
@@ -1451,7 +1498,7 @@ int ieee80211_master_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	if (ieee80211_skb_resize(osdata->local, skb, headroom, may_encrypt)) {
 		dev_kfree_skb(skb);
 		dev_put(odev);
-		return 0;
+		return NETDEV_TX_OK;
 	}
 
 	if (osdata->vif.type == NL80211_IFTYPE_AP_VLAN)
@@ -1460,10 +1507,11 @@ int ieee80211_master_start_xmit(struct sk_buff *skb, struct net_device *dev)
 				      u.ap);
 	if (likely(monitor_iface != UNKNOWN_ADDRESS))
 		info->control.vif = &osdata->vif;
-	ret = ieee80211_tx(odev, skb);
+
+	ieee80211_tx(odev, skb, false);
 	dev_put(odev);
 
-	return ret;
+	return NETDEV_TX_OK;
 }
 
 int ieee80211_monitor_start_xmit(struct sk_buff *skb,
@@ -1827,6 +1875,54 @@ void ieee80211_clear_tx_pending(struct ieee80211_local *local)
 		skb_queue_purge(&local->pending[i]);
 }
 
+static bool ieee80211_tx_pending_skb(struct ieee80211_local *local,
+				     struct sk_buff *skb)
+{
+	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+	struct ieee80211_sub_if_data *sdata;
+	struct sta_info *sta;
+	struct ieee80211_hdr *hdr;
+	struct net_device *dev;
+	int ret;
+	bool result = true;
+
+	/* does interface still exist? */
+	dev = dev_get_by_index(&init_net, skb->iif);
+	if (!dev) {
+		dev_kfree_skb(skb);
+		return true;
+	}
+
+	/* validate info->control.vif against skb->iif */
+	sdata = IEEE80211_DEV_TO_SUB_IF(dev);
+	if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN)
+		sdata = container_of(sdata->bss,
+				     struct ieee80211_sub_if_data,
+				     u.ap);
+
+	if (unlikely(info->control.vif && info->control.vif != &sdata->vif)) {
+		dev_kfree_skb(skb);
+		result = true;
+		goto out;
+	}
+
+	if (info->flags & IEEE80211_TX_INTFL_NEED_TXPROCESSING) {
+		ieee80211_tx(dev, skb, true);
+	} else {
+		hdr = (struct ieee80211_hdr *)skb->data;
+		sta = sta_info_get(local, hdr->addr1);
+
+		ret = __ieee80211_tx(local, &skb, sta);
+		if (ret != IEEE80211_TX_OK)
+			result = false;
+	}
+
+ out:
+	dev_put(dev);
+
+	return result;
+}
+
 /*
  * Transmit all pending packets. Called from tasklet, locks master device
  * TX lock so that no new packets can come in.
@@ -1835,9 +1931,8 @@ void ieee80211_tx_pending(unsigned long data)
 {
 	struct ieee80211_local *local = (struct ieee80211_local *)data;
 	struct net_device *dev = local->mdev;
-	struct ieee80211_hdr *hdr;
 	unsigned long flags;
-	int i, ret;
+	int i;
 	bool next;
 
 	rcu_read_lock();
@@ -1868,13 +1963,8 @@ void ieee80211_tx_pending(unsigned long data)
 
 		while (!skb_queue_empty(&local->pending[i])) {
 			struct sk_buff *skb = skb_dequeue(&local->pending[i]);
-			struct sta_info *sta;
-
-			hdr = (struct ieee80211_hdr *)skb->data;
-			sta = sta_info_get(local, hdr->addr1);
 
-			ret = __ieee80211_tx(local, &skb, sta);
-			if (ret != IEEE80211_TX_OK) {
+			if (!ieee80211_tx_pending_skb(local, skb)) {
 				skb_queue_head(&local->pending[i], skb);
 				break;
 			}