From 310ae9eb2617c62deedef8f121d7ca1ae774fa76 Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Mon, 24 Mar 2025 15:45:32 -0700 Subject: [PATCH] net: designate queue -> napi linking as "ops protected" netdev netlink is the only reader of netdev_{,rx_}queue->napi, and it already holds netdev->lock. Switch protection of the writes to netdev->lock to "ops protected". The expectation will be now that accessing queue->napi will require netdev->lock for "ops locked" drivers, and rtnl_lock for all other drivers. Current "ops locked" drivers don't require any changes. gve and netdevsim use _locked() helpers right next to netif_queue_set_napi() so they must be holding the instance lock. iavf doesn't call it. bnxt is a bit messy but all paths seem locked. Acked-by: Stanislav Fomichev Link: https://patch.msgid.link/20250324224537.248800-7-kuba@kernel.org Signed-off-by: Jakub Kicinski --- include/linux/netdevice.h | 5 +++-- include/net/netdev_lock.h | 8 ++++++++ include/net/netdev_rx_queue.h | 2 +- net/core/dev.c | 3 +-- 4 files changed, 13 insertions(+), 5 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 60ef367d85756..fa79145518d1e 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -710,7 +710,7 @@ struct netdev_queue { * slow- / control-path part */ /* NAPI instance for the queue - * Readers and writers must hold RTNL + * "ops protected", see comment about net_device::lock */ struct napi_struct *napi; @@ -2526,7 +2526,8 @@ struct net_device { * Double ops protects: * @real_num_rx_queues, @real_num_tx_queues * - * Also protects some fields in struct napi_struct. + * Also protects some fields in: + * struct napi_struct, struct netdev_queue, struct netdev_rx_queue * * Ordering: take after rtnl_lock. */ diff --git a/include/net/netdev_lock.h b/include/net/netdev_lock.h index efd302375ef2a..1c0c9a94cc224 100644 --- a/include/net/netdev_lock.h +++ b/include/net/netdev_lock.h @@ -56,6 +56,14 @@ static inline void netdev_ops_assert_locked(const struct net_device *dev) ASSERT_RTNL(); } +static inline void +netdev_ops_assert_locked_or_invisible(const struct net_device *dev) +{ + if (dev->reg_state == NETREG_REGISTERED || + dev->reg_state == NETREG_UNREGISTERING) + netdev_ops_assert_locked(dev); +} + static inline int netdev_lock_cmp_fn(const struct lockdep_map *a, const struct lockdep_map *b) { diff --git a/include/net/netdev_rx_queue.h b/include/net/netdev_rx_queue.h index af40842f229d9..b2238b551dced 100644 --- a/include/net/netdev_rx_queue.h +++ b/include/net/netdev_rx_queue.h @@ -24,7 +24,7 @@ struct netdev_rx_queue { struct xsk_buff_pool *pool; #endif /* NAPI instance for the queue - * Readers and writers must hold RTNL + * "ops protected", see comment about net_device::lock */ struct napi_struct *napi; struct pp_memory_provider_params mp_params; diff --git a/net/core/dev.c b/net/core/dev.c index 2d9be3ecd5e6a..ab74e1f005d2e 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -6901,8 +6901,7 @@ void netif_queue_set_napi(struct net_device *dev, unsigned int queue_index, if (WARN_ON_ONCE(napi && !napi->dev)) return; - if (dev->reg_state >= NETREG_REGISTERED) - ASSERT_RTNL(); + netdev_ops_assert_locked_or_invisible(dev); switch (type) { case NETDEV_QUEUE_TYPE_RX: -- 2.39.5