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([2a0d:3344:5521:6b10:58fd:68f:7756:389d]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47f67466e09sm43781736f8f.21.2026.07.21.09.03.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 21 Jul 2026 09:03:10 -0700 (PDT) Message-ID: <79cdf453-1569-4ae5-b317-2aace4258ecc@redhat.com> Date: Tue, 21 Jul 2026 18:03:09 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next] net/tcp: Prevent inlining tcp_syn_ack_timeout() To: Jakub Kicinski , edumazet@google.com Cc: Emil Tsalapatis , netdev@vger.kernel.org, ncardwell@google.com, kuniyu@google.com, davem@davemloft.net References: <20260708180837.9507-1-emil@etsalapatis.com> <6c01c713-14a8-43c2-aaaf-2fcf622f7e4f@redhat.com> <20260721081240.1b88db50@kernel.org> Content-Language: en-US From: Paolo Abeni In-Reply-To: <20260721081240.1b88db50@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/21/26 5:12 PM, Jakub Kicinski wrote: > On Tue, 21 Jul 2026 15:24:52 +0200 Paolo Abeni wrote: >> On 7/8/26 8:08 PM, Emil Tsalapatis wrote: >>> The tcp_syn_ack_timeout() function gets inlined by Clang, >>> preventing tracing. Since the call is not in the fast >>> path, prevent it from being inlined. >>> >>> Signed-off-by: Emil Tsalapatis >>> --- >>> net/ipv4/tcp_timer.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c >>> index bf171b5e1eb3..f7215d53bbda 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); >>> >> >> What's the point of tracing such function? It just increment a mib. If >> you want to discriminate between TFO and non TFO syn ack timeout, >> possibly adding another MIB counter and incrementing it in >> tcp_fastopen_synack_timer() would be better??? > > FWIW we seem to capture the 5 tuple when it happens, not just mib > counter. Internal commit (form 2019) just says we want to know when > syn-ack is blackholed, unclear under what conditions this happens. Thanks for the context infos. I'm fine with the patch as-is. /P