From b0e28f1effd1d840b36e961edc1def81e01b1ca1 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Thu, 15 Apr 2010 00:14:07 -0700
Subject: [PATCH] net: netif_rx() must disable preemption
Eric Paris reported netif_rx() is calling smp_processor_id() from
preemptible context, in particular when caller is
ip_dev_loopback_xmit().
RPS commit added this smp_processor_id() call, this patch makes sure
preemption is disabled. rps_get_cpus() wants rcu_read_lock() anyway, we
can dot it a bit earlier.
Reported-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
net/core/dev.c | 27 ++++++++++++++++-----------
1 file changed, 16 insertions(+), 11 deletions(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index 876b1112d5ba..e8041eb76ac1 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2206,6 +2206,7 @@ DEFINE_PER_CPU(struct netif_rx_stats, netdev_rx_stat) = { 0, };
/*
* get_rps_cpu is called from netif_receive_skb and returns the target
* CPU from the RPS map of the receiving queue for a given skb.
+ * rcu_read_lock must be held on entry.
*/
static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb)
{
@@ -2217,8 +2218,6 @@ static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb)
u8 ip_proto;
u32 addr1, addr2, ports, ihl;
- rcu_read_lock();
-
if (skb_rx_queue_recorded(skb)) {
u16 index = skb_get_rx_queue(skb);
if (unlikely(index >= dev->num_rx_queues)) {
@@ -2296,7 +2295,6 @@ static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb)
}
done:
- rcu_read_unlock();
return cpu;
}
@@ -2392,7 +2390,7 @@ static int enqueue_to_backlog(struct sk_buff *skb, int cpu)
int netif_rx(struct sk_buff *skb)
{
- int cpu;
+ int ret;
/* if netpoll wants it, pretend we never saw it */
if (netpoll_rx(skb))
@@ -2402,14 +2400,21 @@ int netif_rx(struct sk_buff *skb)
net_timestamp(skb);
#ifdef CONFIG_RPS
- cpu = get_rps_cpu(skb->dev, skb);
- if (cpu < 0)
- cpu = smp_processor_id();
-#else
- cpu = smp_processor_id();
-#endif
+ {
+ int cpu;
- return enqueue_to_backlog(skb, cpu);
+ rcu_read_lock();
+ cpu = get_rps_cpu(skb->dev, skb);
+ if (cpu < 0)
+ cpu = smp_processor_id();
+ ret = enqueue_to_backlog(skb, cpu);
+ rcu_read_unlock();
+ }
+#else
+ ret = enqueue_to_backlog(skb, get_cpu());
+ put_cpu();
+#endif
+ return ret;
}
EXPORT_SYMBOL(netif_rx);