Re: [PATCH net-next] net/tcp: Add explicit tracepoint for tcp_syn_ack_timeout()

["Emil Tsalapatis" <emil@etsalapatis.com>]

On Tue Jul 7, 2026 at 3:52 AM EDT, Eric Dumazet wrote:
> On Mon, Jul 6, 2026 at 6:01 PM Emil Tsalapatis <emil@etsalapatis.com> wrote:
>>
>> Clang can inline the tcp_syn_ack_timeout() function during compilation,
>> making it impossible to use kprobes for tracing without preventing
>> inlining. Add an explicit tracepoint to it instead.
>
> So much copy/pasting for a very small issue :/
>
>>
>> Signed-off-by: Emil Tsalapatis <emil@etsalapatis.com>
>> ---
>>  include/trace/events/tcp.h | 72 ++++++++++++++++++++++++++++++++++++++
>>  net/ipv4/tcp_timer.c       |  3 ++
>>  2 files changed, 75 insertions(+)
>>
>
> tcp_syn_ack_timeout() is hardly a fast path, so you can instead:
>
> diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
> index 322db13333c7..ab2c3de19e46 100644
> --- a/net/ipv4/tcp_timer.c
> +++ b/net/ipv4/tcp_timer.c
> @@ -748,7 +748,7 @@ static void tcp_write_timer(struct timer_list *t)
>         sock_put(sk);
>  }
>
> -void tcp_syn_ack_timeout(const struct request_sock *req)
> +noinline_for_tracing void tcp_syn_ack_timeout(const struct request_sock *req)
>  {
>         struct net *net = read_pnet(&inet_rsk(req)->ireq_net);

Sounds good, I will respin and just mark it noinline.