On Mon, Jul 6, 2026 at 6:01 PM Emil Tsalapatis [off-list ref] 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);