Re: [PATCH] kernel/trace/ftrace: introduce ftrace module notifier

[Steven Rostedt <rostedt@goodmis.org>]

On Thu, 26 Feb 2026 11:51:53 +0100 (CET)
Miroslav Benes <mbenes@suse.cz> wrote:

> > Let me see if there is any way to use notifier and remain below calling
> > sequence:
> > 
> > ftrace_module_enable
> > klp_module_coming
> > blocking_notifier_call_chain_robust(MODULE_STATE_COMING)
> > 
> > blocking_notifier_call_chain(MODULE_STATE_GOING)
> > klp_module_going
> > ftrace_release_mod  
> 
> Both klp and ftrace used module notifiers in the past. We abandoned that 
> and opted for direct calls due to issues with ordering at the time. I do 
> not have the list of problems at hand but I remember it was very fragile.
> 
> See commits 7dcd182bec27 ("ftrace/module: remove ftrace module 
> notifier"), 7e545d6eca20 ("livepatch/module: remove livepatch module 
> notifier") and their surroundings.
> 
> So unless there is a reason for the change (which should be then carefully 
> reviewed and properly tested), I would prefer to keep it as is. What is 
> the motivation? I am failing to find it in the commit log.

Honestly, I do think just decoupling ftrace and live kernel patching from
modules is rationale enough, as it makes the code a bit cleaner. But to do
so, we really need to make sure there is absolutely no regressions.

Thus, to allow such a change, I would ask those that are proposing it, show
a full work flow of how ftrace, live kernel patching, and modules work with
each other and why those functions are currently injected in the module code.

As Miroslav stated, we tried to do it via notifiers in the past and it
failed. I don't want to find out why they failed by just adding them back
to notifiers again. Instead, the reasons must be fully understood and
updates made to make sure they will not fail in the future.

-- Steve