netdev - Re: [PATCH net-next 1/3] net: rps: protect last_qtail with rps_input_queue_tail

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Message-ID: <CAL+tcoD19X_ijKsLQu3cWaLsk8saeEAqQ8MWiJstDMJuWvbNfQ@mail.gmail.com>
Date: Wed, 17 Apr 2024 08:26:18 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, 
	davem@...emloft.net, horms@...nel.org
Cc: netdev@...r.kernel.org, Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next 1/3] net: rps: protect last_qtail with
 rps_input_queue_tail_save() helper

On Tue, Apr 16, 2024 at 3:42 PM Jason Xing <kerneljasonxing@...il.com> wrote:
>
> From: Jason Xing <kernelxing@...cent.com>
>
> Only one left place should be proctected locklessly. This patch made it.
>
> Signed-off-by: Jason Xing <kernelxing@...cent.com>
> ---
>  net/core/dev.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 854a3a28a8d8..cd97eeae8218 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -4501,7 +4501,7 @@ set_rps_cpu(struct net_device *dev, struct sk_buff *skb,
>                 struct netdev_rx_queue *rxqueue;
>                 struct rps_dev_flow_table *flow_table;
>                 struct rps_dev_flow *old_rflow;
> -               u32 flow_id;
> +               u32 flow_id, head;
>                 u16 rxq_index;
>                 int rc;
>
> @@ -4529,8 +4529,8 @@ set_rps_cpu(struct net_device *dev, struct sk_buff *skb,
>                         old_rflow->filter = RPS_NO_FILTER;
>         out:
>  #endif
> -               rflow->last_qtail =
> -                       READ_ONCE(per_cpu(softnet_data, next_cpu).input_queue_head);
> +               head = READ_ONCE(per_cpu(softnet_data, next_cpu).input_queue_head);
> +               rps_input_queue_tail_save(rflow->last_qtail, head);

I made a mistake. I should pass &rflow->last_qtail actually. Will update it.

>         }
>
>         rflow->cpu = next_cpu;
> --
> 2.37.3
>