linux-kernel - Re: [PATCH 2/4] tracing: fix trace_seq

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Message-Id: <1256142035.18347.3133.camel@gandalf.stny.rr.com>
Date:	Wed, 21 Oct 2009 12:20:35 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	mingo@...e.hu, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] tracing: fix trace_seq_printf return value

On Wed, 2009-10-21 at 16:36 +0200, Jiri Olsa wrote:
> I believe we want to return the number of written characters,
> instead of the available buffer length.
> 
> wbr,
> jirka
> 
> Signed-off-by: Jiri Olsa <jolsa@...hat.com>
> ---
>  kernel/trace/trace_output.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
> index ed17565..e871125 100644
> --- a/kernel/trace/trace_output.c
> +++ b/kernel/trace/trace_output.c
> @@ -95,7 +95,7 @@ trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
>  
>  	s->len += ret;
>  
> -	return len;
> +	return ret;

Actually the return value here is ambiguous. Returning len is actually
safer. It probably should only return 0 (buffer not big enough to write
to) or 1 (buffer is big enough).

Because this should actually return non zero:

  trace_seq_printf(s, "");

-- Steve

>  }
>  EXPORT_SYMBOL_GPL(trace_seq_printf);
>  

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