linux-kernel - Re: [PATCH 01/11] [BUGFIX] tracing: Return 0 if event_enable

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Date:	Thu, 09 May 2013 10:31:45 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	linux-kernel@...r.kernel.org,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	yrl.pp-manager.tt@...achi.com, Oleg Nesterov <oleg@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	Tom Zanussi <tom.zanussi@...el.com>
Subject: Re: [PATCH 01/11] [BUGFIX] tracing: Return 0 if event_enable_func
 succeeded

On Thu, 2013-05-09 at 14:44 +0900, Masami Hiramatsu wrote:
> Return 0 instead of the number of activated ftrace if
> event_enable_func succeeded and return an error code if failed,
> beacuse 0 is success code at caller (ftrace_regex_write).
> 
> Without this fix, writing enable_event trigger on set_ftrace_filter
> always doesn't work, since event_enable_func returns 1 to
> ftrace_regex_write, it consumes 1 byte and pass input string
> without the first character again. This makes event_enable_func
> fail and disables event entry.
> 
> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Tom Zanussi <tom.zanussi@...el.com>
> ---
>  kernel/trace/trace_events.c |    5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index 53582e9..44ac836 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -2061,8 +2061,11 @@ event_enable_func(struct ftrace_hash *hash,
>  	if (ret < 0)
>  		goto out_put;
>  	ret = register_ftrace_function_probe(glob, ops, data);
> -	if (!ret)
> +	if (!ret) {
> +		ret = -ENOENT;
>  		goto out_disable;
> +	} else
> +		ret = 0;

I think you meant:

	if (ret < 0)
		goto out_disable;
	ret = 0;

Otherwise, I don't see how you fixed anything, as you still return error
if ret is something other than zero.

Or am I missing something?

-- Steve

>   out:
>  	mutex_unlock(&event_mutex);
>  	return ret;


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