DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6F2C920818
From:   Felix Fietkau <nbd@nbd.name>
To:     linux-wireless@vger.kernel.org
Subject: [PATCH 1/4] mt76: avoid queue/status spinlocks while passing tx status to mac80211
Date:   Tue, 13 Nov 2018 20:41:20 +0100
Message-Id: <20181113194123.93313-1-nbd@nbd.name>
Sender: linux-wireless-owner@vger.kernel.org
Precedence: bulk

There is some code in the mac80211 tx status processing code that could
potentially call back into the tx codepath.
To avoid deadlocks, make sure that no tx related spinlocks are taken
during the ieee80211_tx_status call.

Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 drivers/net/wireless/mediatek/mt76/dma.c      | 11 ++--
 drivers/net/wireless/mediatek/mt76/mac80211.c |  2 +-
 drivers/net/wireless/mediatek/mt76/mt76.h     | 30 ++++------
 .../net/wireless/mediatek/mt76/mt76x02_mac.c  | 11 ++--
 .../net/wireless/mediatek/mt76/mt76x02_util.c |  2 +-
 drivers/net/wireless/mediatek/mt76/tx.c       | 58 ++++++++++++++++---
 6 files changed, 76 insertions(+), 38 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/dma.c b/drivers/net/wireless/mediatek/mt76/dma.c
index 2d7bd26875c6..d62f8d9f2ea1 100644
--- a/drivers/net/wireless/mediatek/mt76/dma.c
+++ b/drivers/net/wireless/mediatek/mt76/dma.c
@@ -157,17 +157,20 @@ mt76_dma_tx_cleanup(struct mt76_dev *dev, enum mt76_txq_id qid, bool flush)
 		if (entry.schedule)
 			q->swq_queued--;
 
-		if (entry.skb)
+		q->tail = (q->tail + 1) % q->ndesc;
+		q->queued--;
+
+		if (entry.skb) {
+			spin_unlock_bh(&q->lock);
 			dev->drv->tx_complete_skb(dev, q, &entry, flush);
+			spin_lock_bh(&q->lock);
+		}
 
 		if (entry.txwi) {
 			mt76_put_txwi(dev, entry.txwi);
 			wake = true;
 		}
 
-		q->tail = (q->tail + 1) % q->ndesc;
-		q->queued--;
-
 		if (!flush && q->tail == last)
 			last = ioread32(&q->regs->dma_idx);
 	}
diff --git a/drivers/net/wireless/mediatek/mt76/mac80211.c b/drivers/net/wireless/mediatek/mt76/mac80211.c
index 85e05a825b5d..3be73b021d27 100644
--- a/drivers/net/wireless/mediatek/mt76/mac80211.c
+++ b/drivers/net/wireless/mediatek/mt76/mac80211.c
@@ -359,7 +359,7 @@ void mt76_unregister_device(struct mt76_dev *dev)
 {
 	struct ieee80211_hw *hw = dev->hw;
 
-	mt76_tx_status_flush(dev, NULL);
+	mt76_tx_status_check(dev, NULL, true);
 	ieee80211_unregister_hw(hw);
 	mt76_tx_free(dev);
 }
diff --git a/drivers/net/wireless/mediatek/mt76/mt76.h b/drivers/net/wireless/mediatek/mt76/mt76.h
index e1d89163ee6b..ea74ba00aebc 100644
--- a/drivers/net/wireless/mediatek/mt76/mt76.h
+++ b/drivers/net/wireless/mediatek/mt76/mt76.h
@@ -648,28 +648,22 @@ void mt76_rx_aggr_stop(struct mt76_dev *dev, struct mt76_wcid *wcid, u8 tid);
 
 void mt76_wcid_key_setup(struct mt76_dev *dev, struct mt76_wcid *wcid,
 			 struct ieee80211_key_conf *key);
+
+void mt76_tx_status_lock(struct mt76_dev *dev, struct sk_buff_head *list)
+			 __acquires(&dev->status_list.lock);
+void mt76_tx_status_unlock(struct mt76_dev *dev, struct sk_buff_head *list)
+			   __releases(&dev->status_list.lock);
+
 int mt76_tx_status_skb_add(struct mt76_dev *dev, struct mt76_wcid *wcid,
 			   struct sk_buff *skb);
 struct sk_buff *mt76_tx_status_skb_get(struct mt76_dev *dev,
-				       struct mt76_wcid *wcid, int pktid);
-void mt76_tx_status_skb_done(struct mt76_dev *dev, struct sk_buff *skb);
+				       struct mt76_wcid *wcid, int pktid,
+				       struct sk_buff_head *list);
+void mt76_tx_status_skb_done(struct mt76_dev *dev, struct sk_buff *skb,
+			     struct sk_buff_head *list);
 void mt76_tx_complete_skb(struct mt76_dev *dev, struct sk_buff *skb);
-
-static inline void
-mt76_tx_status_check(struct mt76_dev *dev)
-{
-	spin_lock_bh(&dev->status_list.lock);
-	mt76_tx_status_skb_get(dev, NULL, 0);
-	spin_unlock_bh(&dev->status_list.lock);
-}
-
-static inline void
-mt76_tx_status_flush(struct mt76_dev *dev, struct mt76_wcid *wcid)
-{
-	spin_lock_bh(&dev->status_list.lock);
-	mt76_tx_status_skb_get(dev, wcid, -1);
-	spin_unlock_bh(&dev->status_list.lock);
-}
+void mt76_tx_status_check(struct mt76_dev *dev, struct mt76_wcid *wcid,
+			  bool flush);
 
 struct ieee80211_sta *mt76_rx_convert(struct sk_buff *skb);
 
diff --git a/drivers/net/wireless/mediatek/mt76/mt76x02_mac.c b/drivers/net/wireless/mediatek/mt76/mt76x02_mac.c
index 59b336e34cb5..4c35d3f7fb15 100644
--- a/drivers/net/wireless/mediatek/mt76/mt76x02_mac.c
+++ b/drivers/net/wireless/mediatek/mt76/mt76x02_mac.c
@@ -438,12 +438,13 @@ void mt76x02_send_tx_status(struct mt76x02_dev *dev,
 	struct mt76_wcid *wcid = NULL;
 	struct mt76x02_sta *msta = NULL;
 	struct mt76_dev *mdev = &dev->mt76;
+	struct sk_buff_head list;
 
 	if (stat->pktid == MT_PACKET_ID_NO_ACK)
 		return;
 
 	rcu_read_lock();
-	spin_lock_bh(&mdev->status_list.lock);
+	mt76_tx_status_lock(mdev, &list);
 
 	if (stat->wcid < ARRAY_SIZE(dev->mt76.wcid))
 		wcid = rcu_dereference(dev->mt76.wcid[stat->wcid]);
@@ -459,7 +460,7 @@ void mt76x02_send_tx_status(struct mt76x02_dev *dev,
 	if (wcid) {
 		if (stat->pktid)
 			status.skb = mt76_tx_status_skb_get(mdev, wcid,
-							    stat->pktid);
+							    stat->pktid, &list);
 		if (status.skb)
 			status.info = IEEE80211_SKB_CB(status.skb);
 	}
@@ -490,12 +491,12 @@ void mt76x02_send_tx_status(struct mt76x02_dev *dev,
 	}
 
 	if (status.skb)
-		mt76_tx_status_skb_done(mdev, status.skb);
+		mt76_tx_status_skb_done(mdev, status.skb, &list);
 	else
 		ieee80211_tx_status_ext(mt76_hw(dev), &status);
 
 out:
-	spin_unlock_bh(&mdev->status_list.lock);
+	mt76_tx_status_unlock(mdev, &list);
 	rcu_read_unlock();
 }
 
@@ -818,7 +819,7 @@ void mt76x02_mac_work(struct work_struct *work)
 	if (!dev->beacon_mask)
 		mt76x02_check_mac_err(dev);
 
-	mt76_tx_status_check(&dev->mt76);
+	mt76_tx_status_check(&dev->mt76, NULL, false);
 
 	ieee80211_queue_delayed_work(mt76_hw(dev), &dev->mac_work,
 				     MT_CALIBRATE_INTERVAL);
diff --git a/drivers/net/wireless/mediatek/mt76/mt76x02_util.c b/drivers/net/wireless/mediatek/mt76/mt76x02_util.c
index 87ce6a51fb05..850b0f050da5 100644
--- a/drivers/net/wireless/mediatek/mt76/mt76x02_util.c
+++ b/drivers/net/wireless/mediatek/mt76/mt76x02_util.c
@@ -215,7 +215,7 @@ int mt76x02_sta_remove(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 	int i;
 
 	mutex_lock(&dev->mt76.mutex);
-	mt76_tx_status_flush(&dev->mt76, &msta->wcid);
+	mt76_tx_status_check(&dev->mt76, &msta->wcid, true);
 	rcu_assign_pointer(dev->mt76.wcid[idx], NULL);
 	for (i = 0; i < ARRAY_SIZE(sta->txq); i++)
 		mt76_txq_remove(&dev->mt76, sta->txq[i]);
diff --git a/drivers/net/wireless/mediatek/mt76/tx.c b/drivers/net/wireless/mediatek/mt76/tx.c
index e6cd583aafd3..e42a24628e4f 100644
--- a/drivers/net/wireless/mediatek/mt76/tx.c
+++ b/drivers/net/wireless/mediatek/mt76/tx.c
@@ -103,8 +103,33 @@ mt76_check_agg_ssn(struct mt76_txq *mtxq, struct sk_buff *skb)
 	mtxq->agg_ssn = le16_to_cpu(hdr->seq_ctrl) + 0x10;
 }
 
+void
+mt76_tx_status_lock(struct mt76_dev *dev, struct sk_buff_head *list)
+		   __acquires(&dev->status_list.lock)
+{
+	__skb_queue_head_init(list);
+	spin_lock_bh(&dev->status_list.lock);
+	__acquire(&dev->status_list.lock);
+}
+EXPORT_SYMBOL_GPL(mt76_tx_status_lock);
+
+void
+mt76_tx_status_unlock(struct mt76_dev *dev, struct sk_buff_head *list)
+		      __releases(&dev->status_list.unlock)
+{
+	struct sk_buff *skb;
+
+	spin_unlock_bh(&dev->status_list.lock);
+	__release(&dev->status_list.unlock);
+
+	while ((skb = __skb_dequeue(list)) != NULL)
+		ieee80211_tx_status(dev->hw, skb);
+}
+EXPORT_SYMBOL_GPL(mt76_tx_status_unlock);
+
 static void
-__mt76_tx_status_skb_done(struct mt76_dev *dev, struct sk_buff *skb, u8 flags)
+__mt76_tx_status_skb_done(struct mt76_dev *dev, struct sk_buff *skb, u8 flags,
+			  struct sk_buff_head *list)
 {
 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 	struct mt76_tx_cb *cb = mt76_tx_skb_cb(skb);
@@ -125,13 +150,14 @@ __mt76_tx_status_skb_done(struct mt76_dev *dev, struct sk_buff *skb, u8 flags)
 		info->flags |= IEEE80211_TX_STAT_ACK;
 	}
 
-	ieee80211_tx_status(dev->hw, skb);
+	__skb_queue_tail(list, skb);
 }
 
 void
-mt76_tx_status_skb_done(struct mt76_dev *dev, struct sk_buff *skb)
+mt76_tx_status_skb_done(struct mt76_dev *dev, struct sk_buff *skb,
+			struct sk_buff_head *list)
 {
-	__mt76_tx_status_skb_done(dev, skb, MT_TX_CB_TXS_DONE);
+	__mt76_tx_status_skb_done(dev, skb, MT_TX_CB_TXS_DONE, list);
 }
 EXPORT_SYMBOL_GPL(mt76_tx_status_skb_done);
 
@@ -173,7 +199,8 @@ mt76_tx_status_skb_add(struct mt76_dev *dev, struct mt76_wcid *wcid,
 EXPORT_SYMBOL_GPL(mt76_tx_status_skb_add);
 
 struct sk_buff *
-mt76_tx_status_skb_get(struct mt76_dev *dev, struct mt76_wcid *wcid, int pktid)
+mt76_tx_status_skb_get(struct mt76_dev *dev, struct mt76_wcid *wcid, int pktid,
+		       struct sk_buff_head *list)
 {
 	struct sk_buff *skb, *tmp;
 
@@ -194,23 +221,36 @@ mt76_tx_status_skb_get(struct mt76_dev *dev, struct mt76_wcid *wcid, int pktid)
 			continue;
 
 		__mt76_tx_status_skb_done(dev, skb, MT_TX_CB_TXS_FAILED |
-						    MT_TX_CB_TXS_DONE);
+						    MT_TX_CB_TXS_DONE, list);
 	}
 
 	return NULL;
 }
 EXPORT_SYMBOL_GPL(mt76_tx_status_skb_get);
 
+void
+mt76_tx_status_check(struct mt76_dev *dev, struct mt76_wcid *wcid, bool flush)
+{
+	struct sk_buff_head list;
+
+	mt76_tx_status_lock(dev, &list);
+	mt76_tx_status_skb_get(dev, wcid, flush ? -1 : 0, &list);
+	mt76_tx_status_unlock(dev, &list);
+}
+EXPORT_SYMBOL_GPL(mt76_tx_status_check);
+
 void mt76_tx_complete_skb(struct mt76_dev *dev, struct sk_buff *skb)
 {
+	struct sk_buff_head list;
+
 	if (!skb->prev) {
 		ieee80211_free_txskb(dev->hw, skb);
 		return;
 	}
 
-	spin_lock_bh(&dev->status_list.lock);
-	__mt76_tx_status_skb_done(dev, skb, MT_TX_CB_DMA_DONE);
-	spin_unlock_bh(&dev->status_list.lock);
+	mt76_tx_status_lock(dev, &list);
+	__mt76_tx_status_skb_done(dev, skb, MT_TX_CB_DMA_DONE, &list);
+	mt76_tx_status_unlock(dev, &list);
 }
 EXPORT_SYMBOL_GPL(mt76_tx_complete_skb);
 
-- 
2.17.0