net: protect NAPI enablement with netdev_lock()

Wrap napi_enable() / napi_disable() with netdev_lock().
Provide the "already locked" flavor of the API.

iavf needs the usual adjustment. A number of drivers call
napi_enable() under a spin lock, so they have to be modified
to take netdev_lock() first, then spin lock then call
napi_enable_locked().

Protecting napi_enable() implies that napi->napi_id is protected
by netdev_lock().

Acked-by: Francois Romieu <romieu@fr.zoreil.com> # via-velocity
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250115035319.559603-7-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/amd/pcnet32.c

@@ -462,7 +462,7 @@ static void pcnet32_netif_start(struct net_device *dev)
 	val = lp->a->read_csr(ioaddr, CSR3);
 	val &= 0x00ff;
 	lp->a->write_csr(ioaddr, CSR3, val);
-	napi_enable(&lp->napi);
+	napi_enable_locked(&lp->napi);
 }
 
 /*
@@ -889,6 +889,7 @@ static int pcnet32_set_ringparam(struct net_device *dev,
 	if (netif_running(dev))
 		pcnet32_netif_stop(dev);
 
+	netdev_lock(dev);
 	spin_lock_irqsave(&lp->lock, flags);
 	lp->a->write_csr(ioaddr, CSR0, CSR0_STOP);	/* stop the chip */
 
@@ -920,6 +921,7 @@ static int pcnet32_set_ringparam(struct net_device *dev,
 	}
 
 	spin_unlock_irqrestore(&lp->lock, flags);
+	netdev_unlock(dev);
 
 	netif_info(lp, drv, dev, "Ring Param Settings: RX: %d, TX: %d\n",
 		   lp->rx_ring_size, lp->tx_ring_size);
@@ -985,6 +987,7 @@ static int pcnet32_loopback_test(struct net_device *dev, uint64_t * data1)
 	if (netif_running(dev))
 		pcnet32_netif_stop(dev);
 
+	netdev_lock(dev);
 	spin_lock_irqsave(&lp->lock, flags);
 	lp->a->write_csr(ioaddr, CSR0, CSR0_STOP);	/* stop the chip */
 
@@ -1122,6 +1125,7 @@ static int pcnet32_loopback_test(struct net_device *dev, uint64_t * data1)
 		lp->a->write_bcr(ioaddr, 20, 4);	/* return to 16bit mode */
 	}
 	spin_unlock_irqrestore(&lp->lock, flags);
+	netdev_unlock(dev);
 
 	return rc;
 }				/* end pcnet32_loopback_test  */
@@ -2101,6 +2105,7 @@ static int pcnet32_open(struct net_device *dev)
 		return -EAGAIN;
 	}
 
+	netdev_lock(dev);
 	spin_lock_irqsave(&lp->lock, flags);
 	/* Check for a valid station address */
 	if (!is_valid_ether_addr(dev->dev_addr)) {
@@ -2266,7 +2271,7 @@ static int pcnet32_open(struct net_device *dev)
 		goto err_free_ring;
 	}
 
-	napi_enable(&lp->napi);
+	napi_enable_locked(&lp->napi);
 
 	/* Re-initialize the PCNET32, and start it when done. */
 	lp->a->write_csr(ioaddr, 1, (lp->init_dma_addr & 0xffff));
@@ -2300,6 +2305,7 @@ static int pcnet32_open(struct net_device *dev)
 		     lp->a->read_csr(ioaddr, CSR0));
 
 	spin_unlock_irqrestore(&lp->lock, flags);
+	netdev_unlock(dev);
 
 	return 0;		/* Always succeed */
 
@@ -2315,6 +2321,7 @@ static int pcnet32_open(struct net_device *dev)
 
 err_free_irq:
 	spin_unlock_irqrestore(&lp->lock, flags);
+	netdev_unlock(dev);
 	free_irq(dev->irq, dev);
 	return rc;
 }

drivers/net/ethernet/intel/iavf/iavf_main.c

@@ -1180,7 +1180,7 @@ static void iavf_napi_enable_all(struct iavf_adapter *adapter)
 
 		q_vector = &adapter->q_vectors[q_idx];
 		napi = &q_vector->napi;
-		napi_enable(napi);
+		napi_enable_locked(napi);
 	}
 }
 
@@ -1196,7 +1196,7 @@ static void iavf_napi_disable_all(struct iavf_adapter *adapter)
 
 	for (q_idx = 0; q_idx < q_vectors; q_idx++) {
 		q_vector = &adapter->q_vectors[q_idx];
-		napi_disable(&q_vector->napi);
+		napi_disable_locked(&q_vector->napi);
 	}
 }
 

drivers/net/ethernet/marvell/mvneta.c

@@ -4392,6 +4392,7 @@ static int mvneta_cpu_online(unsigned int cpu, struct hlist_node *node)
 	if (pp->neta_armada3700)
 		return 0;
 
+	netdev_lock(port->napi.dev);
 	spin_lock(&pp->lock);
 	/*
 	 * Configuring the driver for a new CPU while the driver is
@@ -4418,7 +4419,7 @@ static int mvneta_cpu_online(unsigned int cpu, struct hlist_node *node)
 
 	/* Mask all ethernet port interrupts */
 	on_each_cpu(mvneta_percpu_mask_interrupt, pp, true);
-	napi_enable(&port->napi);
+	napi_enable_locked(&port->napi);
 
 	/*
 	 * Enable per-CPU interrupts on the CPU that is
@@ -4439,6 +4440,8 @@ static int mvneta_cpu_online(unsigned int cpu, struct hlist_node *node)
 		    MVNETA_CAUSE_LINK_CHANGE);
 	netif_tx_start_all_queues(pp->dev);
 	spin_unlock(&pp->lock);
+	netdev_unlock(port->napi.dev);
+
 	return 0;
 }
 

drivers/net/ethernet/via/via-velocity.c

@@ -2320,7 +2320,8 @@ static int velocity_change_mtu(struct net_device *dev, int new_mtu)
 		if (ret < 0)
 			goto out_free_tmp_vptr_1;
 
-		napi_disable(&vptr->napi);
+		netdev_lock(dev);
+		napi_disable_locked(&vptr->napi);
 
 		spin_lock_irqsave(&vptr->lock, flags);
 
@@ -2342,12 +2343,13 @@ static int velocity_change_mtu(struct net_device *dev, int new_mtu)
 
 		velocity_give_many_rx_descs(vptr);
 
-		napi_enable(&vptr->napi);
+		napi_enable_locked(&vptr->napi);
 
 		mac_enable_int(vptr->mac_regs);
 		netif_start_queue(dev);
 
 		spin_unlock_irqrestore(&vptr->lock, flags);
+		netdev_unlock(dev);
 
 		velocity_free_rings(tmp_vptr);
 

include/linux/netdevice.h

@@ -382,7 +382,7 @@ struct napi_struct {
 	struct sk_buff		*skb;
 	struct list_head	rx_list; /* Pending GRO_NORMAL skbs */
 	int			rx_count; /* length of rx_list */
-	unsigned int		napi_id;
+	unsigned int		napi_id; /* protected by netdev_lock */
 	struct hrtimer		timer;
 	struct task_struct	*thread;
 	unsigned long		gro_flush_timeout;
@@ -570,16 +570,11 @@ static inline bool napi_complete(struct napi_struct *n)
 
 int dev_set_threaded(struct net_device *dev, bool threaded);
 
-/**
- *	napi_disable - prevent NAPI from scheduling
- *	@n: NAPI context
- *
- * Stop NAPI from being scheduled on this context.
- * Waits till any outstanding processing completes.
- */
 void napi_disable(struct napi_struct *n);
+void napi_disable_locked(struct napi_struct *n);
 
 void napi_enable(struct napi_struct *n);
+void napi_enable_locked(struct napi_struct *n);
 
 /**
  *	napi_synchronize - wait until NAPI is not running

net/core/dev.c

@@ -6958,11 +6958,13 @@ void netif_napi_add_weight_locked(struct net_device *dev,
 }
 EXPORT_SYMBOL(netif_napi_add_weight_locked);
 
-void napi_disable(struct napi_struct *n)
+void napi_disable_locked(struct napi_struct *n)
 {
 	unsigned long val, new;
 
 	might_sleep();
+	netdev_assert_locked(n->dev);
+
 	set_bit(NAPI_STATE_DISABLE, &n->state);
 
 	val = READ_ONCE(n->state);
@@ -6985,16 +6987,25 @@ void napi_disable(struct napi_struct *n)
 
 	clear_bit(NAPI_STATE_DISABLE, &n->state);
 }
-EXPORT_SYMBOL(napi_disable);
+EXPORT_SYMBOL(napi_disable_locked);
 
 /**
- *	napi_enable - enable NAPI scheduling
- *	@n: NAPI context
+ * napi_disable() - prevent NAPI from scheduling
+ * @n: NAPI context
  *
- * Resume NAPI from being scheduled on this context.
- * Must be paired with napi_disable.
+ * Stop NAPI from being scheduled on this context.
+ * Waits till any outstanding processing completes.
+ * Takes netdev_lock() for associated net_device.
  */
-void napi_enable(struct napi_struct *n)
+void napi_disable(struct napi_struct *n)
+{
+	netdev_lock(n->dev);
+	napi_disable_locked(n);
+	netdev_unlock(n->dev);
+}
+EXPORT_SYMBOL(napi_disable);
+
+void napi_enable_locked(struct napi_struct *n)
 {
 	unsigned long new, val = READ_ONCE(n->state);
 
@@ -7011,6 +7022,22 @@ void napi_enable(struct napi_struct *n)
 			new |= NAPIF_STATE_THREADED;
 	} while (!try_cmpxchg(&n->state, &val, new));
 }
+EXPORT_SYMBOL(napi_enable_locked);
+
+/**
+ * napi_enable() - enable NAPI scheduling
+ * @n: NAPI context
+ *
+ * Enable scheduling of a NAPI instance.
+ * Must be paired with napi_disable().
+ * Takes netdev_lock() for associated net_device.
+ */
+void napi_enable(struct napi_struct *n)
+{
+	netdev_lock(n->dev);
+	napi_enable_locked(n);
+	netdev_unlock(n->dev);
+}
 EXPORT_SYMBOL(napi_enable);
 
 static void flush_gro_hash(struct napi_struct *napi)