linux-kernel - Re: [PATCH v3 02/12] tracing: Add trace_get/put_event

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Date:   Wed, 29 Jan 2020 13:05:04 -0600
From:   Tom Zanussi <zanussi@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     artem.bityutskiy@...ux.intel.com, mhiramat@...nel.org,
        linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org,
        ndesaulniers@...gle.com
Subject: Re: [PATCH v3 02/12] tracing: Add trace_get/put_event_file()

On Wed, 2020-01-29 at 12:52 -0500, Steven Rostedt wrote:
> On Fri, 24 Jan 2020 16:56:13 -0600
> Tom Zanussi <zanussi@...nel.org> wrote:
> 
> > +/**
> > + * trace_put_event_file - Release a file from
> > trace_get_event_file()
> > + * @file: The trace event file
> > + *
> > + * If a file was retrieved using trace_get_event_file(), this
> > should
> > + * be called when it's no longer needed.  It will cancel the
> > previous
> > + * trace_array_get() called by that function, and decrement the
> > + * event's module refcount.
> > + */
> > +void trace_put_event_file(struct trace_event_file *file)
> > +{
> > +	trace_array_put(file->tr);
> > +
> > +	mutex_lock(&event_mutex);
> > +	module_put(file->event_call->mod);
> > +	mutex_unlock(&event_mutex);
> 
> I believe the trace_array_put() needs to be at the end. Otherwise, I
> believe the file could be freed before the event_mutex is taken.
> 
> I'll swap it, as I'm trying to get this into the merge window.

OK, thanks,

Tom

> 
> -- Steve
> 
> > +}
> > +EXPORT_SYMBOL_GPL(trace_put_event_file);
> > +
> >  #ifdef CONFIG_DYNAMIC_FTRACE
> >  
> >  /* Avoid typos */
> 
>