netdev - Re: [PATCH] tcp: tcp_make_synack() can be called from process context

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Message-ID: <CANn89iLypT46pr+ShwXu+k0hYLNwoTjbHJ1eyA_fgZyS5U-1fw@mail.gmail.com>
Date:   Thu, 9 Mar 2023 14:37:50 +0100
From:   Eric Dumazet <edumazet@...gle.com>
To:     Breno Leitao <leitao@...ian.org>
Cc:     davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
        netdev@...r.kernel.org, laurent.fasnacht@...ton.ch,
        hkchu@...gle.com, leit@...a.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tcp: tcp_make_synack() can be called from process context

On Wed, Mar 8, 2023 at 8:07 PM Breno Leitao <leitao@...ian.org> wrote:
>
> tcp_rtx_synack() now could be called in process context as explained in
> 0a375c822497 ("tcp: tcp_rtx_synack() can be called from process
> context").
>
> tcp_rtx_synack() might call tcp_make_synack(), which will touch per-CPU
> variables with preemption enabled. This causes the following BUG:
>
>
> Avoid calling __TCP_INC_STATS() with will touch per-cpu variables. Use
> TCP_INC_STATS() which is safe to be called from context switch.
>
> Fixes: 8336886f786f ("tcp: TCP Fast Open Server - support TFO listeners")
> Signed-off-by: Breno Leitao <leitao@...ian.org>
>

This looks good to me, thanks !

Reviewed-by: Eric Dumazet <edumazet@...gle.com>