Re: [RFC PATCH 0/4] ftrace: Add task comm filtering for function tracing

[Steven Rostedt <rostedt@goodmis.org>]

On Sun, 30 Aug 2026 19:07:43 +0800 (CST)
<hu.shengming@zte.com.cn> wrote:

> Hi Steven and Masami,
> 
> This series adds two comm-based task filters for the function and
> function_graph tracers:
> 
>   set_ftrace_comm
>   set_ftrace_notrace_comm

I'd like to avoid adding more files like this. If anything, I would love to
add triggers to the function tracers.

> 
> Function tracing currently supports selecting tasks by PID. This makes
> it difficult to configure tracing before a service starts, because it
> does not have a PID yet. It is also inconvenient to keep tracing the
> same service across restarts, as its PID may change. This use case was
> suggested by Xuxin, a KSM reviewer.

I've always recommended a simple wrapper script for applications:

echo '#! /bin/bash
  echo $$ > /sys/kernel/tracing/set_ftrace_pid
  echo $$ > /sys/kernel/tracing/set_event_pid
  exec "$@"' > trace-me.sh

chmod +x trace-me.sh

  ./trace-me.sh command to be traced

The above will do what you want.

But if we really do want to add more filters to function tracing, then
adding triggers to it would be the way to go.

-- Steve