netdev - Re: [PATCH net 1/2] i40e: need_wakeup flag might not be set for Tx

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Message-ID: <adee745d-6522-309d-a944-7a54869ac945@mellanox.com>
Date:   Mon, 25 Nov 2019 15:24:33 +0000
From:   Maxim Mikityanskiy <maximmi@...lanox.com>
To:     Magnus Karlsson <magnus.karlsson@...el.com>,
        "bjorn.topel@...el.com" <bjorn.topel@...el.com>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>
CC:     "maciej.fijalkowski@...el.com" <maciej.fijalkowski@...el.com>,
        "maciejromanfijalkowski@...il.com" <maciejromanfijalkowski@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Tariq Toukan <tariqt@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>
Subject: Re: [PATCH net 1/2] i40e: need_wakeup flag might not be set for Tx

Hi Magnus,

On 2019-11-08 21:58, Magnus Karlsson wrote:
> This happens if there is at least one
> outstanding packet that has not been completed by the hardware and we
> get that corresponding completion (which will not generate an
> interrupt since interrupts are disabled in the napi poll loop) between
> the time we stopped processing the Tx completions and interrupts are
> enabled again.

> But if this completion interrupt occurs before interrupts
> are enable, we lose it
Why can't it happen for regular traffic? From your description it looks 
to me as if you can miss a completion for non-AF_XDP traffic, too. Is 
there any detail that makes this issue AF_XDP-specific?

Thanks,
Max