netdev - Re: [PATCH net RFT] bnxt_en: Fix TX timeout during netpoll.

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Date:   Tue, 25 Sep 2018 23:35:50 +0000
From:   Song Liu <songliubraving@...com>
To:     Michael Chan <michael.chan@...adcom.com>
CC:     "edumazet@...gle.com" <edumazet@...gle.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net RFT] bnxt_en: Fix TX timeout during netpoll.

Thanks Michael!

This works well in my tests. 


Reviewed-and-tested-by: Song Liu <songliubraving@...com>


> On Sep 25, 2018, at 2:31 PM, Michael Chan <michael.chan@...adcom.com> wrote:
> 
> The current netpoll implementation in the bnxt_en driver has problems
> that may miss TX completion events.  bnxt_poll_work() in effect is
> only handling at most 1 TX packet before exiting.  In addition,
> there may be in flight TX completions that ->poll() may miss even
> after we fix bnxt_poll_work() to handle all visible TX completions.
> netpoll may not call ->poll() again and HW may not generate IRQ
> because the driver does not ARM the IRQ when the budget (0 for netpoll)
> is reached.
> 
> We fix it by handling all TX completions and to always ARM the IRQ
> when we exit ->poll() with 0 budget.
> 
> Reported-by: Song Liu <songliubraving@...com>
> Signed-off-by: Michael Chan <michael.chan@...adcom.com>
> ---
> drivers/net/ethernet/broadcom/bnxt/bnxt.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> index 61957b0..c981b53 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> @@ -1913,7 +1913,7 @@ static int bnxt_poll_work(struct bnxt *bp, struct bnxt_napi *bnapi, int budget)
> 		}
> 		raw_cons = NEXT_RAW_CMP(raw_cons);
> 
> -		if (rx_pkts == budget)
> +		if (rx_pkts && rx_pkts == budget)
> 			break;
> 	}
> 
> @@ -2027,8 +2027,12 @@ static int bnxt_poll(struct napi_struct *napi, int budget)
> 	while (1) {
> 		work_done += bnxt_poll_work(bp, bnapi, budget - work_done);
> 
> -		if (work_done >= budget)
> +		if (work_done >= budget) {
> +			if (!budget)
> +				BNXT_CP_DB_REARM(cpr->cp_doorbell,
> +						 cpr->cp_raw_cons);
> 			break;
> +		}
> 
> 		if (!bnxt_has_work(bp, cpr)) {
> 			if (napi_complete_done(napi, work_done))
> -- 
> 2.5.1
>