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

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The preempt_disable() () section was introduced in commit
    cece1945bf ("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
    b0e28f1eff ("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
   e30b38c298 ("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 (b0e28f1eff)
should not have been applied only the latter (e30b38c298).

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: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Sebastian Andrzej Siewior 2022-02-12 00:38:37 +01:00 committed by David S. Miller
parent 88f62aea1c
commit f234ae2947
1 changed files with 1 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
net/core/dev.c
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@ -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;
}