linux-kernel - Re: [PATCH] tracing: Show the tracer options in boot-time created instance

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Message-Id: <20251119090602.7605a36b3fbc9184abad7a59@kernel.org>
Date: Wed, 19 Nov 2025 09:06:02 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Mark Rutland <mark.rutland@....com>, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>, Andrew Morton
 <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH] tracing: Show the tracer options in boot-time created
 instance

On Tue, 18 Nov 2025 13:34:34 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Tue, 18 Nov 2025 16:49:50 +0900
> "Masami Hiramatsu (Google)" <mhiramat@...nel.org> wrote:
> 
> > From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> > 
> > Since tracer_init_tracefs_work_func() only updates the tracer options
> > for the global_trace, the instances created by the kernel cmdline
> > do not have those options.
> > 
> > Fix to update tracer options for those boot-time created instances
> > to show those options.
> > 
> > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> > Fixes: f20a580627f43 ("ftrace: Allow instances to use function tracing")
> 
> Actually, I think this should be:
> 
> Fixes: 428add559b69 ("tracing: Have tracer option be instance specific")
> 
> As it broke when we made function tracer options no longer global.
> 

OK, let me change it.

> > ---
> >  kernel/trace/trace.c |    4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> > index 8ae95800592d..2e87060e1d5a 100644
> > --- a/kernel/trace/trace.c
> > +++ b/kernel/trace/trace.c
> > @@ -10903,6 +10903,7 @@ static struct notifier_block trace_module_nb = {
> >  
> >  static __init void tracer_init_tracefs_work_func(struct work_struct *work)
> >  {
> > +	struct trace_array *tr;
> >  
> >  	event_trace_init();
> >  
> > @@ -10937,7 +10938,8 @@ static __init void tracer_init_tracefs_work_func(struct work_struct *work)
> >  
> >  	create_trace_instances(NULL);
> >  
> > -	update_tracer_options(&global_trace);
> > +	list_for_each_entry(tr, &ftrace_trace_arrays, list)
> > +		update_tracer_options(tr);
> >  }
> >  
> >  static __init int tracer_init_tracefs(void)
> 
> Since update_trace_options() is only called by this function, instead of
> doing the loop here, change the function to be:
> 
> static __init void update_tracer_options(void)
> {
> 	struct trace_array *tr;
> 
> 	guard(mutex)(&trace_types_lock);
> 	tracer_options_updated = true;
> 	list_for_each_entry(tr, &ftrace_trace_arrays, list)
> 		__update_tracer_options(tr);
> }

OK. Let me send v2.

Thanks,

> 
> Thanks,
> 
> -- Steve
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>