Commit f234ae29 authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by David S. Miller
Browse files

net: dev: Remove preempt_disable() and get_cpu() in netif_rx_internal(). 

The preempt_disable() () section was introduced in commit
    cece1945 ("net: disable preemption before call smp_processor_id()")

and adds it in case this function is invoked from preemtible context and
because get_cpu() later on as been added.

The get_cpu() usage was added in commit
    b0e28f1e ("net: netif_rx() must disable preemption")

because ip_dev_loopback_xmit() invoked netif_rx() with enabled preemption
causing a warning in smp_processor_id(). The function netif_rx() should
only be invoked from an interrupt context which implies disabled
preemption. The commit
   e30b38c2 ("ip: Fix ip_dev_loopback_xmit()")

was addressing this and replaced netif_rx() with in netif_rx_ni() in
ip_dev_loopback_xmit().

Based on the discussion on the list, the former patch (b0e28f1e)
should not have been applied only the latter (e30b38c2).

Remove get_cpu() and preempt_disable() since the function is supposed to
be invoked from context with stable per-CPU pointers. Bottom halves have
to be disabled at this point because the function may raise softirqs
which need to be processed.

Link: https://lkml.kernel.org/r/20100415.013347.98375530.davem@davemloft.net


Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarToke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 88f62aea

net/core/dev.c

+1 −4
Original line number Diff line number Diff line
@@ -4796,7 +4796,6 @@ static int netif_rx_internal(struct sk_buff *skb) 
		struct rps_dev_flow voidflow, *rflow = &voidflow;

		int cpu;



		preempt_disable();

		rcu_read_lock();



		cpu = get_rps_cpu(skb->dev, skb, &rflow);
@@ -4806,14 +4805,12 @@ static int netif_rx_internal(struct sk_buff *skb) 
		ret = enqueue_to_backlog(skb, cpu, &rflow->last_qtail);



		rcu_read_unlock();

		preempt_enable();

	} else

#endif

	{

		unsigned int qtail;



		ret = enqueue_to_backlog(skb, get_cpu(), &qtail);

		put_cpu();

		ret = enqueue_to_backlog(skb, smp_processor_id(), &qtail);

	}

	return ret;

}