Messages in this thread |  | | Date | Wed, 09 Jan 2013 09:54:59 +0800 | From | Wanlong Gao <> | Subject | Re: [PATCH V3 1/2] virtio-net: fix the set affinity bug when CPU IDs are not consecutive |
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On 01/09/2013 07:31 AM, Rusty Russell wrote: > Wanlong Gao <gaowanlong@cn.fujitsu.com> writes: >> */ >> static u16 virtnet_select_queue(struct net_device *dev, struct sk_buff *skb) >> { >> - int txq = skb_rx_queue_recorded(skb) ? skb_get_rx_queue(skb) : >> - smp_processor_id(); >> + int txq = 0; >> + >> + if (skb_rx_queue_recorded(skb)) >> + txq = skb_get_rx_queue(skb); >> + else if ((txq = per_cpu(vq_index, smp_processor_id())) == -1) >> + txq = 0; > > You should use __get_cpu_var() instead of smp_processor_id() here, ie: > > else if ((txq = __get_cpu_var(vq_index)) == -1) > > And AFAICT, no reason to initialize txq to 0 to start with. > > So: > > int txq; > > if (skb_rx_queue_recorded(skb)) > txq = skb_get_rx_queue(skb); > else { > txq = __get_cpu_var(vq_index); > if (txq == -1) > txq = 0; > }
Got it, thank you.
> > Now, just to confirm, I assume this can happen even if we use vq_index, > right, because of races with virtnet_set_channels?
I still can't understand this race, could you explain more? thank you.
Regards, Wanlong Gao
> > while (unlikely(txq >= dev->real_num_tx_queues)) > txq -= dev->real_num_tx_queues; > > > Thanks, > Rusty. >
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