Subject: [PATCH] net: hns: Ensure that interface teardown cannot race with TX interrupt

From: Marc Zyngier <[email-masked]>
Date: Mon, 4 Nov 2019 19:56:04 +0000

On a lockdep-enabled kernel, bringing down a HNS interface results
in a loud splat. It turns out that  the per-ring spinlock is taken
both in the TX interrupt path, and when bringing down the interface.

Lockdep sums it up with:

[32099.424453]        CPU0
[32099.426885]        ----
[32099.429318]   lock(&(&ring->lock)->rlock);
[32099.433402]   <Interrupt>
[32099.436008]     lock(&(&ring->lock)->rlock);
[32099.440264]
[32099.440264]  *** DEADLOCK ***

To solve this, turn the NETIF_TX_{LOCK,UNLOCK} macros from standard
spin_[un]lock to their irqsave/irqrestore version.

Fixes: f2aaed557ecff ("net: hns: Replace netif_tx_lock to ring spin lock")
Cc: lipeng <[email-masked]>
Cc: Yisen Zhuang <[email-masked]>
Cc: Salil Mehta <[email-masked]>
Cc: David S. Miller <[email-masked]>
Signed-off-by: Marc Zyngier <[email-masked]>
---
 drivers/net/ethernet/hisilicon/hns/hns_enet.c | 22 ++++++++++---------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/drivers/net/ethernet/hisilicon/hns/hns_enet.c b/drivers/net/ethernet/hisilicon/hns/hns_enet.c
index a48396dd4ebb..9fbe4e1e6853 100644
--- a/drivers/net/ethernet/hisilicon/hns/hns_enet.c
+++ b/drivers/net/ethernet/hisilicon/hns/hns_enet.c
@@ -945,11 +945,11 @@ static int is_valid_clean_head(struct hnae_ring *ring, int h)
 
 /* netif_tx_lock will turn down the performance, set only when necessary */
 #ifdef CONFIG_NET_POLL_CONTROLLER
-#define NETIF_TX_LOCK(ring) spin_lock(&(ring)->lock)
-#define NETIF_TX_UNLOCK(ring) spin_unlock(&(ring)->lock)
+#define NETIF_TX_LOCK(ring, flags) spin_lock_irqsave(&(ring)->lock, flags)
+#define NETIF_TX_UNLOCK(ring, flags) spin_unlock_irqrestore(&(ring)->lock, flags)
 #else
-#define NETIF_TX_LOCK(ring)
-#define NETIF_TX_UNLOCK(ring)
+#define NETIF_TX_LOCK(ring, flags)
+#define NETIF_TX_UNLOCK(ring, flags)
 #endif
 
 /* reclaim all desc in one budget
@@ -962,16 +962,17 @@ static int hns_nic_tx_poll_one(struct hns_nic_ring_data *ring_data,
 	struct net_device *ndev = ring_data->napi.dev;
 	struct netdev_queue *dev_queue;
 	struct hns_nic_priv *priv = netdev_priv(ndev);
+	unsigned long flags;
 	int head;
 	int bytes, pkts;
 
-	NETIF_TX_LOCK(ring);
+	NETIF_TX_LOCK(ring, flags);
 
 	head = readl_relaxed(ring->io_base + RCB_REG_HEAD);
 	rmb(); /* make sure head is ready before touch any data */
 
 	if (is_ring_empty(ring) || head == ring->next_to_clean) {
-		NETIF_TX_UNLOCK(ring);
+		NETIF_TX_UNLOCK(ring, flags);
 		return 0; /* no data to poll */
 	}
 
@@ -979,7 +980,7 @@ static int hns_nic_tx_poll_one(struct hns_nic_ring_data *ring_data,
 		netdev_err(ndev, "wrong head (%d, %d-%d)\n", head,
 			   ring->next_to_use, ring->next_to_clean);
 		ring->stats.io_err_cnt++;
-		NETIF_TX_UNLOCK(ring);
+		NETIF_TX_UNLOCK(ring, flags);
 		return -EIO;
 	}
 
@@ -994,7 +995,7 @@ static int hns_nic_tx_poll_one(struct hns_nic_ring_data *ring_data,
 	ring->stats.tx_pkts += pkts;
 	ring->stats.tx_bytes += bytes;
 
-	NETIF_TX_UNLOCK(ring);
+	NETIF_TX_UNLOCK(ring, flags);
 
 	dev_queue = netdev_get_tx_queue(ndev, ring_data->queue_index);
 	netdev_tx_completed_queue(dev_queue, pkts, bytes);
@@ -1052,10 +1053,11 @@ static void hns_nic_tx_clr_all_bufs(struct hns_nic_ring_data *ring_data)
 	struct hnae_ring *ring = ring_data->ring;
 	struct net_device *ndev = ring_data->napi.dev;
 	struct netdev_queue *dev_queue;
+	unsigned long flags;
 	int head;
 	int bytes, pkts;
 
-	NETIF_TX_LOCK(ring);
+	NETIF_TX_LOCK(ring, flags);
 
 	head = ring->next_to_use; /* ntu :soft setted ring position*/
 	bytes = 0;
@@ -1063,7 +1065,7 @@ static void hns_nic_tx_clr_all_bufs(struct hns_nic_ring_data *ring_data)
 	while (head != ring->next_to_clean)
 		hns_nic_reclaim_one_desc(ring, &bytes, &pkts);
 
-	NETIF_TX_UNLOCK(ring);
+	NETIF_TX_UNLOCK(ring, flags);
 
 	dev_queue = netdev_get_tx_queue(ndev, ring_data->queue_index);
 	netdev_tx_reset_queue(dev_queue);
-- 
2.20.1