Subject: [PATCH net-next v2 09/11] net: protect napi->irq with netdev_lock()

From: Jakub Kicinski <[email-masked]>
Date: Tue, 14 Jan 2025 19:53:17 -0800

Take netdev_lock() in netif_napi_set_irq(). All NAPI "control fields"
are now protected by that lock (most of the other ones are set during
napi add/del). The napi_hash_node is fully protected by the hash
spin lock, but close enough for the kdoc...

Reviewed-by: Joe Damato <[email-masked]>
Reviewed-by: Eric Dumazet <[email-masked]>
Signed-off-by: Jakub Kicinski <[email-masked]>
---
 include/linux/netdevice.h | 10 +++++++++-
 net/core/dev.c            |  2 +-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index bf3da95c9350..390fb70667bf 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -388,6 +388,7 @@ struct napi_struct {
 	unsigned long		gro_flush_timeout;
 	unsigned long		irq_suspend_timeout;
 	u32			defer_hard_irqs;
+	/* all fields past this point are write-protected by netdev_lock */
 	/* control-path-only fields follow */
 	struct list_head	dev_list;
 	struct hlist_node	napi_hash_node;
@@ -2706,11 +2707,18 @@ static inline void netdev_assert_locked_or_invisible(struct net_device *dev)
 		netdev_assert_locked(dev);
 }
 
-static inline void netif_napi_set_irq(struct napi_struct *napi, int irq)
+static inline void netif_napi_set_irq_locked(struct napi_struct *napi, int irq)
 {
 	napi->irq = irq;
 }
 
+static inline void netif_napi_set_irq(struct napi_struct *napi, int irq)
+{
+	netdev_lock(napi->dev);
+	netif_napi_set_irq_locked(napi, irq);
+	netdev_unlock(napi->dev);
+}
+
 /* Default NAPI poll() weight
  * Device drivers are strongly advised to not use bigger value
  */
diff --git a/net/core/dev.c b/net/core/dev.c
index d90bb100285d..495ceefcdc34 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6956,7 +6956,7 @@ void netif_napi_add_weight_locked(struct net_device *dev,
 	 */
 	if (dev->threaded && napi_kthread_create(napi))
 		dev->threaded = false;
-	netif_napi_set_irq(napi, -1);
+	netif_napi_set_irq_locked(napi, -1);
 }
 EXPORT_SYMBOL(netif_napi_add_weight_locked);
 
-- 
2.48.0