netdev - Re: [PATCH net] bnxt: do not busy-poll when link is down

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Date:   Tue, 22 Nov 2016 10:38:36 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Andy Gospodarek <gospo@...adcom.com>
Cc:     netdev@...r.kernel.org, Michael Chan <michael.chan@...adcom.com>
Subject: Re: [PATCH net] bnxt: do not busy-poll when link is down

On Tue, 2016-11-22 at 13:14 -0500, Andy Gospodarek wrote:
> When busy polling while a link is down (during a link-flap test), TX
> timeouts were observed as well as the following messages in the ring
> buffer:
> 
> bnxt_en 0008:01:00.2 enP8p1s0f2d2: Resp cmpl intr err msg: 0x51
> bnxt_en 0008:01:00.2 enP8p1s0f2d2: hwrm_ring_free tx failed. rc:-1
> bnxt_en 0008:01:00.2 enP8p1s0f2d2: Resp cmpl intr err msg: 0x51
> bnxt_en 0008:01:00.2 enP8p1s0f2d2: hwrm_ring_free rx failed. rc:-1
> 
> These were resolved by checking for link status and returning if link
> was not up.
> 
> Signed-off-by: Andy Gospodarek <gospo@...adcom.com>
> Signed-off-by: Michael Chan <michael.chan@...adcom.com>
> Tested-by: Rob Miller <rob.miller@...adcom.com>
> ---
>  drivers/net/ethernet/broadcom/bnxt/bnxt.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> index e18635b..013e373 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> @@ -1811,6 +1811,9 @@ static int bnxt_busy_poll(struct napi_struct *napi)
>  	if (atomic_read(&bp->intr_sem) != 0)
>  		return LL_FLUSH_FAILED;
>  
> +	if (!bp->link_info.link_up)
> +		return LL_FLUSH_FAILED;
> +
>  	if (!bnxt_lock_poll(bnapi))
>  		return LL_FLUSH_BUSY;
>  


Any plans removing this busy polling stuff, now it is done in core
networking stack ?

This would remove bnxt_lock_napi() extra overhead in normal path ( napi
poll )

I could do this but I do not have the hardware to do the tests.