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

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Date:   Wed, 29 Jan 2020 12:52:55 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Tom Zanussi <zanussi@...nel.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 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.

-- Steve

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