netdev - Re: [PATCH RFC net-next] trace: tcp: Add tracepoint for tcp_cwnd

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Message-ID: <20250120100340.4129eff7@batman.local.home>
Date: Mon, 20 Jan 2025 10:03:40 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Breno Leitao <leitao@...ian.org>
Cc: Jason Xing <kerneljasonxing@...il.com>, Eric Dumazet
 <edumazet@...gle.com>, Masami Hiramatsu <mhiramat@...nel.org>, Mathieu
 Desnoyers <mathieu.desnoyers@...icios.com>, "David S. Miller"
 <davem@...emloft.net>, David Ahern <dsahern@...nel.org>, Jakub Kicinski
 <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Simon Horman
 <horms@...nel.org>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, kernel-team@...a.com, Yonghong Song
 <yonghong.song@...ux.dev>, Song Liu <song@...nel.org>, Martin KaFai Lau
 <martin.lau@...nel.org>
Subject: Re: [PATCH RFC net-next] trace: tcp: Add tracepoint for
 tcp_cwnd_reduction()

On Mon, 20 Jan 2025 05:20:05 -0800
Breno Leitao <leitao@...ian.org> wrote:

> This patch enhances the API's stability by introducing a guaranteed hook
> point, allowing the compiler to make changes without disrupting the
> BPF program's functionality.

Instead of using a TRACE_EVENT() macro, you can use DECLARE_TRACE()
which will create the tracepoint in the kernel, but will not create a
trace event that is exported to the tracefs file system. Then BPF could
hook to it and it will still not be exposed as an user space API.

You can see its use in include/trace/events/sched.h

-- Steve