linux-kernel - Re: [Intel-wired-lan] [PATCH] e1000e: Fix TX dispatch condition

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Date:   Wed, 9 Nov 2022 13:19:42 +0200
From:   "naamax.meir" <naamax.meir@...ux.intel.com>
To:     Akihiko Odaki <akihiko.odaki@...nix.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Yuri Benditovich <yuri.benditovich@...nix.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Yan Vugenfirer <yan@...nix.com>,
        intel-wired-lan@...ts.osuosl.org, Paolo Abeni <pabeni@...hat.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [Intel-wired-lan] [PATCH] e1000e: Fix TX dispatch condition

On 10/13/2022 08:00, Akihiko Odaki wrote:
> e1000_xmit_frame is expected to stop the queue and dispatch frames to
> hardware if there is not sufficient space for the next frame in the
> buffer, but sometimes it failed to do so because the estimated maxmium
> size of frame was wrong. As the consequence, the later invocation of
> e1000_xmit_frame failed with NETDEV_TX_BUSY, and the frame in the buffer
> remained forever, resulting in a watchdog failure.
> 
> This change fixes the estimated size by making it match with the
> condition for NETDEV_TX_BUSY. Apparently, the old estimation failed to
> account for the following lines which determines the space requirement
> for not causing NETDEV_TX_BUSY:
>> 	/* reserve a descriptor for the offload context */
>> 	if ((mss) || (skb->ip_summed == CHECKSUM_PARTIAL))
>> 		count++;
>> 	count++;
>>
>> 	count += DIV_ROUND_UP(len, adapter->tx_fifo_limit);
> 
> This issue was found with http-stress02 test included in Linux Test
> Project 20220930.
> 
> Signed-off-by: Akihiko Odaki <akihiko.odaki@...nix.com>
> ---
>   drivers/net/ethernet/intel/e1000e/netdev.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
Tested-by: Naama Meir <naamax.meir@...ux.intel.com>