netdev - Re: [PATCH net-next v2 2/2] tcp: add more warn of socket in tcp_send_loss

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Message-ID: <CANn89iLmyNnRn27mSy_fYacvacUoNh=fy2qzCP-1tcL5g_r3vg@mail.gmail.com>
Date: Tue, 22 Oct 2024 10:00:25 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: Jason Xing <kerneljasonxing@...il.com>
Cc: davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com, 
	dsahern@...nel.org, ncardwell@...gle.com, netdev@...r.kernel.org, 
	Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next v2 2/2] tcp: add more warn of socket in tcp_send_loss_probe()

On Mon, Oct 21, 2024 at 5:53 PM Jason Xing <kerneljasonxing@...il.com> wrote:
>
> From: Jason Xing <kernelxing@...cent.com>
>
> Add two fields to print in the helper which here covers tcp_send_loss_probe().
>
> Link: https://lore.kernel.org/all/5632e043-bdba-4d75-bc7e-bf58014492fd@redhat.com/
> Suggested-by: Paolo Abeni <pabeni@...hat.com>
> Signed-off-by: Jason Xing <kernelxing@...cent.com>
> Cc: Neal Cardwell <ncardwell@...gle.com>
> --
> v2
> Link:https://lore.kernel.org/all/CAL+tcoAr7RHhaZGV12wYDcPPPaubAqdxMCmy7Jujtr8b3+bY=w@mail.gmail.com/
> 1. use "" instead of NULL in tcp_send_loss_probe()
> ---
>  include/net/tcp.h     | 4 +++-
>  net/ipv4/tcp_output.c | 4 +---
>  2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index 8b8d94bb1746..78158169e944 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -2433,12 +2433,14 @@ void tcp_plb_update_state_upon_rto(struct sock *sk, struct tcp_plb_state *plb);
>  static inline void tcp_warn_once(const struct sock *sk, bool cond, const char *str)
>  {
>         WARN_ONCE(cond,
> -                 "%sout:%u sacked:%u lost:%u retrans:%u tlp_high_seq:%u sk_state:%u ca_state:%u advmss:%u mss_cache:%u pmtu:%u\n",
> +                 "%scwn:%u out:%u sacked:%u lost:%u retrans:%u tlp_high_seq:%u sk_state:%u ca_state:%u mss:%u advmss:%u mss_cache:%u pmtu:%u\n",
>                   str,
> +                 tcp_snd_cwnd(tcp_sk(sk)),
>                   tcp_sk(sk)->packets_out, tcp_sk(sk)->sacked_out,
>                   tcp_sk(sk)->lost_out, tcp_sk(sk)->retrans_out,
>                   tcp_sk(sk)->tlp_high_seq, sk->sk_state,
>                   inet_csk(sk)->icsk_ca_state,
> +                 tcp_current_mss((struct sock *)sk),

You can not promote to non const, because tcp_current_mss() might
change socket state.

If a debug helper changes the socket state, then it is no longer a debug helper.

>                   tcp_sk(sk)->advmss, tcp_sk(sk)->mss_cache,

This was already reported btw.

>                   inet_csk(sk)->icsk_pmtu_cookie);
>  }
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index 054244ce5117..36562b5fe290 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -2954,9 +2954,7 @@ void tcp_send_loss_probe(struct sock *sk)
>         }
>         skb = skb_rb_last(&sk->tcp_rtx_queue);
>         if (unlikely(!skb)) {
> -               WARN_ONCE(tp->packets_out,
> -                         "invalid inflight: %u state %u cwnd %u mss %d\n",
> -                         tp->packets_out, sk->sk_state, tcp_snd_cwnd(tp), mss);
> +               tcp_warn_once(sk, tp->packets_out, "");
>                 smp_store_release(&inet_csk(sk)->icsk_pending, 0);
>                 return;
>         }
> --
> 2.37.3
>