linux-kernel - Re: [PATCH] fgraph: Do not enable function_graph tracer when setting funcgraph-args

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Message-ID: <20250617230024.322758dc@gandalf.local.home>
Date: Tue, 17 Jun 2025 23:00:24 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: duchangbin <changbin.du@...wei.com>
Cc: LKML <linux-kernel@...r.kernel.org>, Linux Trace Kernel
 <linux-trace-kernel@...r.kernel.org>, Masami Hiramatsu
 <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH] fgraph: Do not enable function_graph tracer when
 setting funcgraph-args

On Wed, 18 Jun 2025 02:40:21 +0000
duchangbin <changbin.du@...wei.com> wrote:

> > diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
> > index 9234e2c39abf..b6211c304c7f 100644
> > --- a/kernel/trace/trace_functions_graph.c
> > +++ b/kernel/trace/trace_functions_graph.c
> > @@ -455,10 +455,16 @@ static int graph_trace_init(struct trace_array *tr)
> >  	return 0;
> >  }
> >  
> > +static struct tracer graph_trace;
> > +
> >  static int ftrace_graph_trace_args(struct trace_array *tr, int set)
> >  {
> >  	trace_func_graph_ent_t entry;
> >  
> > +	/* Do nothing if the current tracer is no this tracer */  
> typo: no -> not

Oops, thanks.

> 
> > +	if (tr->current_trace != &graph_trace)
> > +		return 0;
> > +  
> This can fix the issue. But how are tr->current_trace and &graph_trace linked?
> When are they equal?

register_tracer() passes in what tr->current_trace gets set to when the
tracer is active.

-- Steve


> 
> >  	if (set)
> >  		entry = trace_graph_entry_args;
> >  	else
> > -- 
> > 2.47.2