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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 15 Dec 2021 12:47:30 +0100
Subject: [PATCH 3/4] net: dev: Makes sure netif_rx() can be invoked in any
context.
Dave suggested a while ago (11y 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 halfs to ensure that to
ensure that pending softirqs, which were raised within the function, are
handled.
netif_rx_ni() can be invoked only from preemptible context because the
function handles pending softirqs without checking if bottom halfes 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 halfs while invoking
netif_rx_internal(). The local_bh_enable() invokcation will then invoke
pending softirqs only if the BH-disable counter drops to zero.
Add a local_bh_disable() section in netif_rx() to ensure softirqs are
handled if needed. 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@davemloft.net
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
include/linux/netdevice.h | 13 +++++++++++--
include/trace/events/net.h | 14 --------------
net/core/dev.c | 34 ++--------------------------------
3 files changed, 13 insertions(+), 48 deletions(-)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3668,8 +3668,17 @@ u32 bpf_prog_run_generic_xdp(struct sk_b
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);
+
+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);
--- a/include/trace/events/net.h
+++ b/include/trace/events/net.h
@@ -260,13 +260,6 @@ DEFINE_EVENT(net_dev_rx_verbose_template
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),
@@ -309,13 +302,6 @@ DEFINE_EVENT(net_dev_rx_exit_template, n
TP_PROTO(int ret),
- TP_ARGS(ret)
-);
-
-DEFINE_EVENT(net_dev_rx_exit_template, netif_rx_ni_exit,
-
- TP_PROTO(int ret),
-
TP_ARGS(ret)
);
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4834,47 +4834,17 @@ int netif_rx(struct sk_buff *skb)
{
int ret;
+ local_bh_disable();
trace_netif_rx_entry(skb);
ret = netif_rx_internal(skb);
trace_netif_rx_exit(ret);
+ 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);
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