Re: [PATCH net-next] virtio_net: ethtool tx napi configuration

[Jason Wang <jasowang@redhat.com>]

On 2018年09月14日 12:46, Willem de Bruijn wrote:
>> I'm not sure I get this. If we don't enable tx napi, we tend to delay TX
>> interrupt if we found the ring is about to full to avoid interrupt
>> storm, so we're probably ok in this case.
> I'm only concerned about the transition state when converting from
> napi to no-napi when the queue is stopped and tx interrupt disabled.
>
> With napi mode the interrupt is only disabled if napi is scheduled,
> in which case it will eventually reenable the interrupt. But when
> switching to no-napi mode in this state no progress will be made.
>
> But it seems this cannot happen. When converting to no-napi
> mode, set_coalesce waits for napi to complete in napi_disable.
> So the interrupt should always start enabled when transitioning
> into no-napi mode.

An update, I meet a hang in napi_disalbe(). But it's hard to be 
reproduced. I tend to choose a easy way like V1 that only allow the 
switching when device is down.

I will post the patch after a vacation. (or you can post if it was 
urgent for you).

Thanks