Re: [RFC PATCH bpf-next v3 1/2] ftrace: deprecate disabling via ftrace_enabled sysctl

On Thu, Aug 6, 2026 at 8:30 AM Andrey Grodzovsky
<[email protected]> wrote:
>
> Writing 0 to kernel.ftrace_enabled has not reliably disabled ftrace
> for years (FTRACE_OPS_FL_PERMANENT users already block it, and more
> callers rely on ftrace always being on). Refuse the write instead of
> leaving it in an inconsistent "disables some, not all" state: return
> -EOPNOTSUPP and log a message. Reads and enabling (writing 1) are
> unaffected.
>
> Update the docs to note the deprecation up front.
>
> Suggested-by: Steven Rostedt <[email protected]>
> Signed-off-by: Andrey Grodzovsky <[email protected]>

Sashiko's comments make sense. Other than those:

Acked-by: Song Liu <[email protected]>

> ---
>  Documentation/trace/ftrace.rst |  5 ++++
>  kernel/trace/ftrace.c          | 43 +++++-----------------------------
>  2 files changed, 11 insertions(+), 37 deletions(-)
>