Dave suggested a while ago (eleven years by now) "Let's make netif_rx() work in all contexts and get rid of netif_rx_ni()". Eric agreed and pointed out that modern devices should use netif_receive_skb() to avoid the overhead. In the meantime someone added another variant, netif_rx_any_context(), which behaves as suggested. netif_rx() must be invoked with disabled bottom halves to ensure that pending softirqs, which were raised within the function, are handled. netif_rx_ni() can be invoked only from process context (bottom halves must be enabled) because the function handles pending softirqs without checking if bottom halves were disabled or not. netif_rx_any_context() invokes on the former functions by checking in_interrupts(). netif_rx() could be taught to handle both cases (disabled and enabled bottom halves) by simply disabling bottom halves while invoking netif_rx_internal(). The local_bh_enable() invocation will then invoke pending softirqs only if the BH-disable counter drops to zero. Eric is concerned about the overhead of BH-disable+enable especially in regard to the loopback driver. As critical as this driver is, it will receive a shortcut to avoid the additional overhead which is not needed. Add a local_bh_disable() section in netif_rx() to ensure softirqs are handled if needed. Provide the internal bits as __netif_rx() which can be used by the loopback driver. This function is not exported so it can't be used by modules. Make netif_rx_ni() and netif_rx_any_context() invoke netif_rx() so they can be removed once they are no more users left. Link: https://lkml.kernel.org/r/20100415.020246.218622820.davem@xxxxxxxxxxxxx Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx> --- drivers/net/loopback.c | 2 +- include/linux/netdevice.h | 14 ++++++++-- include/trace/events/net.h | 14 ---------- net/core/dev.c | 53 +++++++++++--------------------------- 4 files changed, 28 insertions(+), 55 deletions(-) diff --git a/drivers/net/loopback.c b/drivers/net/loopback.c index ed0edf5884ef8..77f5b564382b6 100644 --- a/drivers/net/loopback.c +++ b/drivers/net/loopback.c @@ -86,7 +86,7 @@ static netdev_tx_t loopback_xmit(struct sk_buff *skb, skb->protocol = eth_type_trans(skb, dev); len = skb->len; - if (likely(netif_rx(skb) == NET_RX_SUCCESS)) + if (likely(__netif_rx(skb) == NET_RX_SUCCESS)) dev_lstats_add(dev, len); return NETDEV_TX_OK; diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index e490b84732d16..c9e883104adb1 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -3669,8 +3669,18 @@ u32 bpf_prog_run_generic_xdp(struct sk_buff *skb, struct xdp_buff *xdp, void generic_xdp_tx(struct sk_buff *skb, struct bpf_prog *xdp_prog); int do_xdp_generic(struct bpf_prog *xdp_prog, struct sk_buff *skb); int netif_rx(struct sk_buff *skb); -int netif_rx_ni(struct sk_buff *skb); -int netif_rx_any_context(struct sk_buff *skb); +int __netif_rx(struct sk_buff *skb); + +static inline int netif_rx_ni(struct sk_buff *skb) +{ + return netif_rx(skb); +} + +static inline int netif_rx_any_context(struct sk_buff *skb) +{ + return netif_rx(skb); +} + int netif_receive_skb(struct sk_buff *skb); int netif_receive_skb_core(struct sk_buff *skb); void netif_receive_skb_list_internal(struct list_head *head); diff --git a/include/trace/events/net.h b/include/trace/events/net.h index 78c448c6ab4c5..032b431b987b6 100644 --- a/include/trace/events/net.h +++ b/include/trace/events/net.h @@ -260,13 +260,6 @@ DEFINE_EVENT(net_dev_rx_verbose_template, netif_rx_entry, TP_ARGS(skb) ); -DEFINE_EVENT(net_dev_rx_verbose_template, netif_rx_ni_entry, - - TP_PROTO(const struct sk_buff *skb), - - TP_ARGS(skb) -); - DECLARE_EVENT_CLASS(net_dev_rx_exit_template, TP_PROTO(int ret), @@ -312,13 +305,6 @@ DEFINE_EVENT(net_dev_rx_exit_template, netif_rx_exit, TP_ARGS(ret) ); -DEFINE_EVENT(net_dev_rx_exit_template, netif_rx_ni_exit, - - TP_PROTO(int ret), - - TP_ARGS(ret) -); - DEFINE_EVENT(net_dev_rx_exit_template, netif_receive_skb_list_exit, TP_PROTO(int ret), diff --git a/net/core/dev.c b/net/core/dev.c index 0d13340ed4054..f34a8f3a448a7 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -4815,6 +4815,16 @@ static int netif_rx_internal(struct sk_buff *skb) return ret; } +int __netif_rx(struct sk_buff *skb) +{ + int ret; + + trace_netif_rx_entry(skb); + ret = netif_rx_internal(skb); + trace_netif_rx_exit(ret); + return ret; +} + /** * netif_rx - post buffer to the network code * @skb: buffer to post @@ -4823,58 +4833,25 @@ static int netif_rx_internal(struct sk_buff *skb) * the upper (protocol) levels to process. It always succeeds. The buffer * may be dropped during processing for congestion control or by the * protocol layers. + * This interface is considered legacy. Modern NIC driver should use NAPI + * and GRO. * * return values: * NET_RX_SUCCESS (no congestion) * NET_RX_DROP (packet was dropped) * */ - int netif_rx(struct sk_buff *skb) { int ret; - trace_netif_rx_entry(skb); - - ret = netif_rx_internal(skb); - trace_netif_rx_exit(ret); - + local_bh_disable(); + ret = __netif_rx(skb); + local_bh_enable(); return ret; } EXPORT_SYMBOL(netif_rx); -int netif_rx_ni(struct sk_buff *skb) -{ - int err; - - trace_netif_rx_ni_entry(skb); - - preempt_disable(); - err = netif_rx_internal(skb); - if (local_softirq_pending()) - do_softirq(); - preempt_enable(); - trace_netif_rx_ni_exit(err); - - return err; -} -EXPORT_SYMBOL(netif_rx_ni); - -int netif_rx_any_context(struct sk_buff *skb) -{ - /* - * If invoked from contexts which do not invoke bottom half - * processing either at return from interrupt or when softrqs are - * reenabled, use netif_rx_ni() which invokes bottomhalf processing - * directly. - */ - if (in_interrupt()) - return netif_rx(skb); - else - return netif_rx_ni(skb); -} -EXPORT_SYMBOL(netif_rx_any_context); - static __latent_entropy void net_tx_action(struct softirq_action *h) { struct softnet_data *sd = this_cpu_ptr(&softnet_data); -- 2.34.1
