netdev - Re: [PATCH v2 net-next] net: core: use listified Rx for GRO_NORMAL in napi_gro

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Date:   Tue, 26 Nov 2019 15:57:46 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     alobakin@...nk.ru
Cc:     pabeni@...hat.com, johannes@...solutions.net, ecree@...arflare.com,
        nicholas.johnson-opensource@...look.com.au, jiri@...lanox.com,
        edumazet@...gle.com, idosch@...lanox.com, petrm@...lanox.com,
        sd@...asysnail.net, f.fainelli@...il.com,
        jaswinder.singh@...aro.org, ilias.apalodimas@...aro.org,
        linux-kernel@...r.kernel.org, emmanuel.grumbach@...el.com,
        luciano.coelho@...el.com, linuxwifi@...el.com,
        kvalo@...eaurora.org, netdev@...r.kernel.org,
        linux-wireless@...r.kernel.org
Subject: Re: [PATCH v2 net-next] net: core: use listified Rx for GRO_NORMAL
 in napi_gro_receive()

From: Alexander Lobakin <alobakin@...nk.ru>
Date: Mon, 25 Nov 2019 15:02:24 +0300

> Paolo Abeni wrote 25.11.2019 14:42:
>> For -net, I *think* something as dumb and hacky as the following could
>> possibly work:
>> ----
>> diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
>> b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
>> index 4bba6b8a863c..df82fad96cbb 100644
>> --- a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
>> +++ b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
>> @@ -1527,7 +1527,7 @@ static void iwl_pcie_rx_handle(struct iwl_trans
>> *trans, int queue)
>>                 iwl_pcie_rxq_alloc_rbs(trans, GFP_ATOMIC, rxq);
>>         if (rxq->napi.poll)
>> -               napi_gro_flush(&rxq->napi, false);
>> +               napi_complete_done(&rxq->napi, 0);
>>         iwl_pcie_rxq_restock(trans, rxq);
>>  }
>> ---
> 
> napi_complete_done(napi, 0) has an equivalent static inline
> napi_complete(napi). I'm not sure it will work without any issues
> as iwlwifi doesn't _really_ turn NAPI into scheduling state.
> 
> I'm not very familiar with iwlwifi, but as a work around manual
> napi_gro_flush() you can also manually flush napi->rx_list to
> prevent packets from stalling:
> 
> diff -Naur a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
> b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c
> --- a/drivers/net/wireless/intel/iwlwifi/pcie/rx.c 2019-11-25
> --- 14:55:03.610355230 +0300
> +++ b/drivers/net/wireless/intel/iwlwifi/pcie/rx.c 2019-11-25
> 14:57:29.399556868 +0300
 ...

Thanks to everyone for looking into this.

Can I get some kind of fix in the next 24 hours?  I want to send a quick
follow-on pull request to Linus to deal with all of the fallout, and in
particular fix this regression.

Thanks!