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From:   Menglong Dong <menglong8.dong@gmail.com>
Date:   Mon, 9 Nov 2020 22:48:37 +0800
Message-ID: <CADxym3bP=BRbVAnDCzmrrAyh3i=QO3gAWnUwpU==TskFY-GHYg@mail.gmail.com>
Subject: Re: [PATCH] net: tcp: ratelimit warnings in tcp_recvmsg
To:     Eric Dumazet <edumazet@google.com>
Cc:     David Miller <davem@davemloft.net>,
        Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        Jakub Kicinski <kuba@kernel.org>,
        netdev <netdev@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Menglong Dong <dong.menglong@zte.com.cn>
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On Mon, Nov 9, 2020 at 9:36 PM Eric Dumazet <edumazet@google.com> wrote:
>
> I do not think this patch is useful. That is simply code churn.
>
> Can you trigger the WARN() in the latest upstream version ?
> If yes this is a serious bug that needs urgent attention.
>
> Make sure you have backported all needed fixes into your kernel, if
> you get this warning on a non pristine kernel.

Theoretically, this WARN() shouldn't be triggered in any branches.
Somehow, it just happened in kernel v3.10. This really confused me. I
wasn't able to keep tracing it, as it is a product environment.

I notice that the codes for tcp skb receiving didn't change much
between v3.10 and the latest upstream version, and guess the latest
version can be triggered too.

If something is fixed and this WARN() won't be triggered, just ignore me.

Cheers,
Menglong Dong