linux-kernel - Re: [PATCH] net/core: Export dev_core_stats_rx_dropped

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Message-ID: <CANn89iKbn97Rbjc+3uZMpUi0tqCuhj88UdFZhhnqpC6nJRLC=A@mail.gmail.com>
Date:   Tue, 12 Sep 2023 20:05:42 +0200
From:   Eric Dumazet <edumazet@...gle.com>
To:     Alexander Lobakin <aleksander.lobakin@...el.com>
Cc:     Yajun Deng <yajun.deng@...ux.dev>, davem@...emloft.net,
        kuba@...nel.org, pabeni@...hat.com, horms@...nel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net/core: Export dev_core_stats_rx_dropped_inc sets

On Tue, Sep 12, 2023 at 8:03 PM Eric Dumazet <edumazet@...gle.com> wrote:

> Sure, this was what was suggested (perhaps not _very_ precisely, but
> the general idea was pretty clear).
> v2 seems ok, right ?
>
> It seems we are all on the same page.
>
> +static __cold struct net_device_core_stats __percpu
> *dev_core_stats(struct net_device *dev)
> +{
> +       /* This READ_ONCE() pairs with the write in netdev_core_stats_alloc() */
> +       struct net_device_core_stats __percpu *p = READ_ONCE(dev->core_stats);
> +
> +       if (likely(p))
> +               return p;
> +
> +       return netdev_core_stats_alloc(dev);
> +}
> +
> +#define DEV_CORE_STATS_INC(FIELD)                              \
> +void dev_core_stats_##FIELD##_inc(struct net_device *dev)      \
> +{                                                              \
> +       struct net_device_core_stats __percpu *p;               \
> +                                                               \
> +       p = dev_core_stats(dev);                                \
> +       if (p)                                                  \
> +               this_cpu_inc(p->FIELD);                         \
> +}                                                              \
> +EXPORT_SYMBOL(dev_core_stats_##FIELD##_inc)

Oh well, I just read the patch, and it seems wrong indeed.

netdev_core_stats_alloc() is the one that can be cold.