netdev - Re: [PATCH net 00/15] netpoll: avoid capture effects for NAPI drivers

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Date:   Mon, 24 Sep 2018 12:41:20 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     songliubraving@...com
Cc:     David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>, michael.chan@...adcom.com,
        Ariel Elior <ariel.elior@...ium.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        jakub.kicinski@...ronome.com, Jay Vosburgh <j.vosburgh@...il.com>,
        Veaceslav Falico <vfalico@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>
Subject: Re: [PATCH net 00/15] netpoll: avoid capture effects for NAPI drivers

On Mon, Sep 24, 2018 at 12:31 PM Song Liu <songliubraving@...com> wrote:

> This triggers dev_watchdog() on a simple netperf TCP_RR on bnxt (I haven't
> tested other drivers yet).
>
> I guess this is because NAPI_STATE_SCHED is set when poll_one_napi() calls
> napi->poll(). And then cleared by napi->poll().

Which part of napi->poll() could possibly clear NAPI_STATE_SCHED when
called by netpoll ?

AFAIK, napi_complete_done() should exit early (before having a chance
to clear NAPI_STATE_SCHED)
because of :

if (unlikely(n->state & (NAPIF_STATE_NPSVC | NAPIF_STATE_IN_BUSY_POLL)))
     return false;

Thanks !