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Commit b0e28f1e authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

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: default avatarEric Paris <eparis@redhat.com>
Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent fea06915

net/core/dev.c

+15 −10
Original line number Diff line number Diff line
@@ -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 @@ got_hash: 
	}



done:

	rcu_read_unlock();

	return cpu;

}
@@ -2392,7 +2390,7 @@ enqueue: 


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

	{

		int 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

	cpu = smp_processor_id();

	ret = enqueue_to_backlog(skb, get_cpu());

	put_cpu();

#endif



	return enqueue_to_backlog(skb, cpu);

	return ret;

}

EXPORT_SYMBOL(netif_rx);