iwlwifi: mvm: fix aggregation drain flow

Move the counter for non-AMPDU frames to mvm. It is needed
for the drain flow which happens once the ieee80211_sta has
been freed, so keeping it in iwl_mvm_sta which is embed into
ieee80211_sta is not a good idea.

Also, since its purpose it to remove the STA in the fw only
after all the frames for this station have exited the shared
Tx queues, we need to decrement it in the reclaim flow. This
flow can happen after ieee80211_sta has been removed, which
means that we have no iwl_mvm_sta there. So we can't know
what is the vif type. Hence, we know audit these frames for
all the vif types.
In order to avoid spawning sta_drained_wk all the time, we
now check that we are in a flow in which draining might
happen - only when mvmsta is NULL. This is better than
previous code that would spawn sta_drained_wk all the time
in AP mode.

Cc: stable@vger.kernel.org [3.9]
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Reviewed-by: Ilan Peer <ilan.peer@intel.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/iwlwifi/mvm/mac80211.c

@@ -946,7 +946,7 @@ static void iwl_mvm_mac_sta_notify(struct ieee80211_hw *hw,
 
 	switch (cmd) {
 	case STA_NOTIFY_SLEEP:
-		if (atomic_read(&mvmsta->pending_frames) > 0)
+		if (atomic_read(&mvm->pending_frames[mvmsta->sta_id]) > 0)
 			ieee80211_sta_block_awake(hw, sta, true);
 		/*
 		 * The fw updates the STA to be asleep. Tx packets on the Tx

drivers/net/wireless/iwlwifi/mvm/mvm.h

@@ -292,6 +292,7 @@ struct iwl_mvm {
 	struct ieee80211_sta __rcu *fw_id_to_mac_id[IWL_MVM_STATION_COUNT];
 	struct work_struct sta_drained_wk;
 	unsigned long sta_drained[BITS_TO_LONGS(IWL_MVM_STATION_COUNT)];
+	atomic_t pending_frames[IWL_MVM_STATION_COUNT];
 
 	/* configured by mac80211 */
 	u32 rts_threshold;

drivers/net/wireless/iwlwifi/mvm/sta.c

@@ -219,7 +219,7 @@ int iwl_mvm_add_sta(struct iwl_mvm *mvm,
 	mvm_sta->max_agg_bufsize = LINK_QUAL_AGG_FRAME_LIMIT_DEF;
 
 	/* HW restart, don't assume the memory has been zeroed */
-	atomic_set(&mvm_sta->pending_frames, 0);
+	atomic_set(&mvm->pending_frames[sta_id], 0);
 	mvm_sta->tid_disable_agg = 0;
 	mvm_sta->tfd_queue_msk = 0;
 	for (i = 0; i < IEEE80211_NUM_ACS; i++)
@@ -406,15 +406,22 @@ int iwl_mvm_rm_sta(struct iwl_mvm *mvm,
 		mvmvif->ap_sta_id = IWL_MVM_STATION_COUNT;
 	}
 
+	/*
+	 * Make sure that the tx response code sees the station as -EBUSY and
+	 * calls the drain worker.
+	 */
+	spin_lock_bh(&mvm_sta->lock);
 	/*
 	 * There are frames pending on the AC queues for this station.
 	 * We need to wait until all the frames are drained...
 	 */
-	if (atomic_read(&mvm_sta->pending_frames)) {
-		ret = iwl_mvm_drain_sta(mvm, mvm_sta, true);
+	if (atomic_read(&mvm->pending_frames[mvm_sta->sta_id])) {
 		rcu_assign_pointer(mvm->fw_id_to_mac_id[mvm_sta->sta_id],
 				   ERR_PTR(-EBUSY));
+		spin_unlock_bh(&mvm_sta->lock);
+		ret = iwl_mvm_drain_sta(mvm, mvm_sta, true);
 	} else {
+		spin_unlock_bh(&mvm_sta->lock);
 		ret = iwl_mvm_rm_sta_common(mvm, mvm_sta->sta_id);
 		rcu_assign_pointer(mvm->fw_id_to_mac_id[mvm_sta->sta_id], NULL);
 	}

drivers/net/wireless/iwlwifi/mvm/sta.h

@@ -274,7 +274,6 @@ struct iwl_mvm_tid_data {
  * @bt_reduced_txpower: is reduced tx power enabled for this station
  * @lock: lock to protect the whole struct. Since %tid_data is access from Tx
  * and from Tx response flow, it needs a spinlock.
- * @pending_frames: number of frames for this STA on the shared Tx queues.
  * @tid_data: per tid data. Look at %iwl_mvm_tid_data.
  *
  * When mac80211 creates a station it reserves some space (hw->sta_data_size)
@@ -290,7 +289,6 @@ struct iwl_mvm_sta {
 	u8 max_agg_bufsize;
 	bool bt_reduced_txpower;
 	spinlock_t lock;
-	atomic_t pending_frames;
 	struct iwl_mvm_tid_data tid_data[IWL_MAX_TID_COUNT];
 	struct iwl_lq_sta lq_sta;
 	struct ieee80211_vif *vif;

drivers/net/wireless/iwlwifi/mvm/tx.c

@@ -416,9 +416,8 @@ int iwl_mvm_tx_skb(struct iwl_mvm *mvm, struct sk_buff *skb,
 
 	spin_unlock(&mvmsta->lock);
 
-	if (mvmsta->vif->type == NL80211_IFTYPE_AP &&
-	    txq_id < IWL_MVM_FIRST_AGG_QUEUE)
-		atomic_inc(&mvmsta->pending_frames);
+	if (txq_id < IWL_MVM_FIRST_AGG_QUEUE)
+		atomic_inc(&mvm->pending_frames[mvmsta->sta_id]);
 
 	return 0;
 
@@ -680,16 +679,41 @@ static void iwl_mvm_rx_tx_cmd_single(struct iwl_mvm *mvm,
 	/*
 	 * If the txq is not an AMPDU queue, there is no chance we freed
 	 * several skbs. Check that out...
-	 * If there are no pending frames for this STA, notify mac80211 that
-	 * this station can go to sleep in its STA table.
 	 */
-	if (txq_id < IWL_MVM_FIRST_AGG_QUEUE && mvmsta &&
-	    !WARN_ON(skb_freed > 1) &&
-	    mvmsta->vif->type == NL80211_IFTYPE_AP &&
-	    atomic_sub_and_test(skb_freed, &mvmsta->pending_frames)) {
-		ieee80211_sta_block_awake(mvm->hw, sta, false);
-		set_bit(sta_id, mvm->sta_drained);
-		schedule_work(&mvm->sta_drained_wk);
+	if (txq_id < IWL_MVM_FIRST_AGG_QUEUE && !WARN_ON(skb_freed > 1) &&
+	    atomic_sub_and_test(skb_freed, &mvm->pending_frames[sta_id])) {
+		if (mvmsta) {
+			/*
+			 * If there are no pending frames for this STA, notify
+			 * mac80211 that this station can go to sleep in its
+			 * STA table.
+			 */
+			if (mvmsta->vif->type == NL80211_IFTYPE_AP)
+				ieee80211_sta_block_awake(mvm->hw, sta, false);
+			/*
+			 * We might very well have taken mvmsta pointer while
+			 * the station was being removed. The remove flow might
+			 * have seen a pending_frame (because we didn't take
+			 * the lock) even if now the queues are drained. So make
+			 * really sure now that this the station is not being
+			 * removed. If it is, run the drain worker to remove it.
+			 */
+			spin_lock_bh(&mvmsta->lock);
+			sta = rcu_dereference(mvm->fw_id_to_mac_id[sta_id]);
+			if (IS_ERR_OR_NULL(sta)) {
+				/*
+				 * Station disappeared in the meantime:
+				 * so we are draining.
+				 */
+				set_bit(sta_id, mvm->sta_drained);
+				schedule_work(&mvm->sta_drained_wk);
+			}
+			spin_unlock_bh(&mvmsta->lock);
+		} else if (!mvmsta) {
+			/* Tx response without STA, so we are draining */
+			set_bit(sta_id, mvm->sta_drained);
+			schedule_work(&mvm->sta_drained_wk);
+		}
 	}
 
 	rcu_read_unlock();