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

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Date:	Wed, 21 Oct 2009 18:14:07 -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 Thu, 2009-10-22 at 00:02 +0200, Jiri Olsa wrote:
> On Wed, Oct 21, 2009 at 12:20:35PM -0400, Steven Rostedt wrote:
> > 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);
> > >  
> >
> 
> I made the suggested fix, plus spot not used function.
> 
> ---
> Making trace_seq_printf return 0 if the trace oversizes the buffer's free
> space, 1 otherwise.  Removing not used trace_seq_vprintf function.

err, I hate to remove that function. This is a utility file that is
exported for other parts of the kernel to use. At least make that a
separate patch.

-- Steve


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