[PATCH] net/rps: consolidate RPS dispatch into netif_rps() helpers
From: Jemmy Wong <hidden>
Date: 2026-07-02 15:28:47
Also in:
lkml
Subsystem:
networking drivers, networking [general], the rest · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
From: "Jemmy Wong" <redacted> The RPS steering logic in netif_rx_internal(), netif_receive_skb_internal() and netif_receive_skb_list_internal() was open-coded three times, each with its own #ifdef CONFIG_RPS block and manual rcu_read_lock()/unlock() pairs. Factor it into two helpers, netif_rps() for the single-skb path and netif_rps_list() for the list path, and switch the callers to guard(rcu)/scoped_guard(rcu). A new internal NET_RX_UNHANDLED sentinel lets a helper report "RPS did not take this skb" so the caller falls back to the local enqueue / __netif_receive_skb() path; it never escapes to callers. netif_rps_list() keeps the early static_branch_unlikely(&rps_needed) bail out so the list is not needlessly walked and re-spliced when RPS is compiled in but disabled. No functional change intended. Signed-off-by: Jemmy Wong <redacted> --- include/linux/netdevice.h | 5 ++- net/core/dev.c | 94 +++++++++++++++++++-------------------- 2 files changed, 48 insertions(+), 51 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 9981d637f8b5..c265b78082e3 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h@@ -93,8 +93,9 @@ void netdev_set_default_ethtool_ops(struct net_device *dev, void netdev_sw_irq_coalesce_default_on(struct net_device *dev); /* Backlog congestion levels */ -#define NET_RX_SUCCESS 0 /* keep 'em coming, baby */ -#define NET_RX_DROP 1 /* packet dropped */ +#define NET_RX_UNHANDLED -1 +#define NET_RX_SUCCESS 0 +#define NET_RX_DROP 1 #define MAX_NEST_DEV 8
diff --git a/net/core/dev.c b/net/core/dev.c
index 4b3d5cfdf6e0..259f8c8e5657 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c@@ -5426,6 +5426,38 @@ static int enqueue_to_backlog(struct sk_buff *skb, int cpu, return NET_RX_DROP; } +static inline int netif_rps(struct sk_buff *skb) +{ +#ifdef CONFIG_RPS + if (static_branch_unlikely(&rps_needed)) { + struct rps_dev_flow voidflow, *rflow = &voidflow; + int cpu = get_rps_cpu(skb->dev, skb, &rflow); + + if (cpu >= 0) + return enqueue_to_backlog(skb, cpu, &rflow->last_qtail); + } +#endif + return NET_RX_UNHANDLED; +} + +static inline void netif_rps_list(struct list_head *head) +{ +#ifdef CONFIG_RPS + struct sk_buff *skb, *next; + LIST_HEAD(undo_list); + + if (!static_branch_unlikely(&rps_needed)) + return; + + list_for_each_entry_safe(skb, next, head, list) { + skb_list_del_init(skb); + if (netif_rps(skb) == NET_RX_UNHANDLED) + list_add_tail(&skb->list, &undo_list); + } + list_splice_init(&undo_list, head); +#endif +} + static struct netdev_rx_queue *netif_get_rxqueue(struct sk_buff *skb) { struct net_device *dev = skb->dev;
@@ -5695,33 +5727,20 @@ EXPORT_SYMBOL_GPL(do_xdp_generic); static int netif_rx_internal(struct sk_buff *skb) { - int ret; + int ret = NET_RX_UNHANDLED; + unsigned int qtail; net_timestamp_check(READ_ONCE(net_hotdata.tstamp_prequeue), skb); trace_netif_rx(skb); -#ifdef CONFIG_RPS - if (static_branch_unlikely(&rps_needed)) { - struct rps_dev_flow voidflow, *rflow = &voidflow; - int cpu; - - rcu_read_lock(); - - cpu = get_rps_cpu(skb->dev, skb, &rflow); - if (cpu < 0) - cpu = smp_processor_id(); + scoped_guard(rcu) + ret = netif_rps(skb); + if (ret != NET_RX_UNHANDLED) + return ret; - ret = enqueue_to_backlog(skb, cpu, &rflow->last_qtail); + ret = enqueue_to_backlog(skb, smp_processor_id(), &qtail); - rcu_read_unlock(); - } else -#endif - { - unsigned int qtail; - - ret = enqueue_to_backlog(skb, smp_processor_id(), &qtail); - } return ret; }
@@ -6389,21 +6408,12 @@ static int netif_receive_skb_internal(struct sk_buff *skb) if (skb_defer_rx_timestamp(skb)) return NET_RX_SUCCESS; - rcu_read_lock(); -#ifdef CONFIG_RPS - if (static_branch_unlikely(&rps_needed)) { - struct rps_dev_flow voidflow, *rflow = &voidflow; - int cpu = get_rps_cpu(skb->dev, skb, &rflow); + guard(rcu)(); + ret = netif_rps(skb); + if (ret != NET_RX_UNHANDLED) + return ret; - if (cpu >= 0) { - ret = enqueue_to_backlog(skb, cpu, &rflow->last_qtail); - rcu_read_unlock(); - return ret; - } - } -#endif ret = __netif_receive_skb(skb); - rcu_read_unlock(); return ret; }
@@ -6421,23 +6431,9 @@ void netif_receive_skb_list_internal(struct list_head *head) } list_splice_init(&sublist, head); - rcu_read_lock(); -#ifdef CONFIG_RPS - if (static_branch_unlikely(&rps_needed)) { - list_for_each_entry_safe(skb, next, head, list) { - struct rps_dev_flow voidflow, *rflow = &voidflow; - int cpu = get_rps_cpu(skb->dev, skb, &rflow); - - if (cpu >= 0) { - /* Will be handled, remove from list */ - skb_list_del_init(skb); - enqueue_to_backlog(skb, cpu, &rflow->last_qtail); - } - } - } -#endif + guard(rcu)(); + netif_rps_list(head); __netif_receive_skb_list(head); - rcu_read_unlock(); } /** --
2.25.1