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Message-ID: <20090102154805.GA6833@nowhere>
Date: Fri, 2 Jan 2009 16:48:06 +0100
From: Frederic Weisbecker <fweisbec@...il.com>
To: Roel Kluin <roel.kluin@...il.com>
Cc: Steven Rostedt <rostedt@...dmis.org>,
lkml <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] ftrace: unsigned idx cannot be less than 0
On Fri, Jan 02, 2009 at 03:49:43PM +0100, Roel Kluin wrote:
> // vi kernel/trace/ftrace.c +787
> struct ftrace_iterator {
> ...
> unsigned idx;
> ...
> };
>
> idx is unsigned and cannot be less than 0.
>
> Signed-off-by: Roel Kluin <roel.kluin@...il.com>
> ---
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 2f32969..a344add 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -842,7 +842,7 @@ static void *t_start(struct seq_file *m, loff_t *pos)
> void *p = NULL;
>
> if (*pos > 0) {
> - if (iter->idx < 0)
> + if (iter->idx == 0)
> return p;
> (*pos)--;
> iter->idx--;
Hi Roel,
I'm not sure this is the right fix.
If you look at t_next, if there is no more page to look at,
iter_idx takes -1.
A 0 value would mean: we are in the first index on the page, which means
there is something to read and we don't want to return NULL.
I guess that would be better to turn idx into a signed int.
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