netdev - Re: [PATCH net v1] mlxbf_gige: fix receive packet race condition

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Message-ID: <20220919141736.53155bb2@kernel.org>
Date:   Mon, 19 Sep 2022 14:17:36 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     David Thompson <davthompson@...dia.com>
Cc:     <davem@...emloft.net>, <edumazet@...gle.com>, <pabeni@...hat.com>,
        <netdev@...r.kernel.org>, <cai.huoqing@...ux.dev>, <brgl@...ev.pl>,
        <limings@...dia.com>, Asmaa Mnebhi <asmaa@...dia.com>
Subject: Re: [PATCH net v1] mlxbf_gige: fix receive packet race condition

On Thu, 8 Sep 2022 16:28:53 -0400 David Thompson wrote:
> Under heavy traffic, the BF2 Gigabit interface can
> become unresponsive for periods of time (several minutes)
> before eventually recovering.  This is due to a possible
> race condition in the mlxbf_gige_rx_packet function, where
> the function exits with producer and consumer indices equal
> but there are remaining packet(s) to be processed. In order
> to prevent this situation, disable receive DMA during the
> processing of received packets.

Pausing Rx DMA seems a little drastic, is the capacity of the NIC
buffer large enough to sink the traffic while the stack drains 
the ring?

Could you provide a little more detail on what the HW issue is? 
There is no less intrusive way we can fix it?