netdev - [PATCH net v2] net: macb: Fix tx_ptr

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Message-Id: <20250829143521.1686062-1-sean.anderson@linux.dev>
Date: Fri, 29 Aug 2025 10:35:21 -0400
From: Sean Anderson <sean.anderson@...ux.dev>
To: Andrew Lunn <andrew+netdev@...n.ch>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org
Cc: Claudiu Beznea <claudiu.beznea@...on.dev>,
	linux-kernel@...r.kernel.org,
	Nicolas Ferre <nicolas.ferre@...rochip.com>,
	Mike Galbraith <efault@....de>,
	Robert Hancock <robert.hancock@...ian.com>,
	Sean Anderson <sean.anderson@...ux.dev>
Subject: [PATCH net v2] net: macb: Fix tx_ptr_lock locking

macb_start_xmit and macb_tx_poll can be called with bottom-halves
disabled (e.g. from softirq) as well as with interrupts disabled (with
netpoll). Because of this, all other functions taking tx_ptr_lock must
use spin_lock_irqsave.

Fixes: 138badbc21a0 ("net: macb: use NAPI for TX completion path")
Reported-by: Mike Galbraith <efault@....de>
Signed-off-by: Sean Anderson <sean.anderson@...ux.dev>
---

Changes in v2:
- Use irqsave/restore for all accesses, since they can also also be
  called from netpoll.

 drivers/net/ethernet/cadence/macb_main.c | 28 ++++++++++++++----------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 16d28a8b3b56..c769b7dbd3ba 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -1223,12 +1223,13 @@ static int macb_tx_complete(struct macb_queue *queue, int budget)
 {
 	struct macb *bp = queue->bp;
 	u16 queue_index = queue - bp->queues;
+	unsigned long flags;
 	unsigned int tail;
 	unsigned int head;
 	int packets = 0;
 	u32 bytes = 0;
 
-	spin_lock(&queue->tx_ptr_lock);
+	spin_lock_irqsave(&queue->tx_ptr_lock, flags);
 	head = queue->tx_head;
 	for (tail = queue->tx_tail; tail != head && packets < budget; tail++) {
 		struct macb_tx_skb	*tx_skb;
@@ -1291,7 +1292,7 @@ static int macb_tx_complete(struct macb_queue *queue, int budget)
 	    CIRC_CNT(queue->tx_head, queue->tx_tail,
 		     bp->tx_ring_size) <= MACB_TX_WAKEUP_THRESH(bp))
 		netif_wake_subqueue(bp->dev, queue_index);
-	spin_unlock(&queue->tx_ptr_lock);
+	spin_unlock_irqrestore(&queue->tx_ptr_lock, flags);
 
 	return packets;
 }
@@ -1707,8 +1708,9 @@ static void macb_tx_restart(struct macb_queue *queue)
 {
 	struct macb *bp = queue->bp;
 	unsigned int head_idx, tbqp;
+	unsigned long flags;
 
-	spin_lock(&queue->tx_ptr_lock);
+	spin_lock_irqsave(&queue->tx_ptr_lock, flags);
 
 	if (queue->tx_head == queue->tx_tail)
 		goto out_tx_ptr_unlock;
@@ -1720,19 +1722,20 @@ static void macb_tx_restart(struct macb_queue *queue)
 	if (tbqp == head_idx)
 		goto out_tx_ptr_unlock;
 
-	spin_lock_irq(&bp->lock);
+	spin_lock(&bp->lock);
 	macb_writel(bp, NCR, macb_readl(bp, NCR) | MACB_BIT(TSTART));
-	spin_unlock_irq(&bp->lock);
+	spin_unlock(&bp->lock);
 
 out_tx_ptr_unlock:
-	spin_unlock(&queue->tx_ptr_lock);
+	spin_unlock_irqrestore(&queue->tx_ptr_lock, flags);
 }
 
 static bool macb_tx_complete_pending(struct macb_queue *queue)
 {
 	bool retval = false;
+	unsigned long flags;
 
-	spin_lock(&queue->tx_ptr_lock);
+	spin_lock_irqsave(&queue->tx_ptr_lock, flags);
 	if (queue->tx_head != queue->tx_tail) {
 		/* Make hw descriptor updates visible to CPU */
 		rmb();
@@ -1740,7 +1743,7 @@ static bool macb_tx_complete_pending(struct macb_queue *queue)
 		if (macb_tx_desc(queue, queue->tx_tail)->ctrl & MACB_BIT(TX_USED))
 			retval = true;
 	}
-	spin_unlock(&queue->tx_ptr_lock);
+	spin_unlock_irqrestore(&queue->tx_ptr_lock, flags);
 	return retval;
 }
 
@@ -2308,6 +2311,7 @@ static netdev_tx_t macb_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	struct macb_queue *queue = &bp->queues[queue_index];
 	unsigned int desc_cnt, nr_frags, frag_size, f;
 	unsigned int hdrlen;
+	unsigned long flags;
 	bool is_lso;
 	netdev_tx_t ret = NETDEV_TX_OK;
 
@@ -2368,7 +2372,7 @@ static netdev_tx_t macb_start_xmit(struct sk_buff *skb, struct net_device *dev)
 		desc_cnt += DIV_ROUND_UP(frag_size, bp->max_tx_length);
 	}
 
-	spin_lock_bh(&queue->tx_ptr_lock);
+	spin_lock_irqsave(&queue->tx_ptr_lock, flags);
 
 	/* This is a hard error, log it. */
 	if (CIRC_SPACE(queue->tx_head, queue->tx_tail,
@@ -2392,15 +2396,15 @@ static netdev_tx_t macb_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	netdev_tx_sent_queue(netdev_get_tx_queue(bp->dev, queue_index),
 			     skb->len);
 
-	spin_lock_irq(&bp->lock);
+	spin_lock(&bp->lock);
 	macb_writel(bp, NCR, macb_readl(bp, NCR) | MACB_BIT(TSTART));
-	spin_unlock_irq(&bp->lock);
+	spin_unlock(&bp->lock);
 
 	if (CIRC_SPACE(queue->tx_head, queue->tx_tail, bp->tx_ring_size) < 1)
 		netif_stop_subqueue(dev, queue_index);
 
 unlock:
-	spin_unlock_bh(&queue->tx_ptr_lock);
+	spin_unlock_irqrestore(&queue->tx_ptr_lock, flags);
 
 	return ret;
 }
-- 
2.35.1.1320.gc452695387.dirty