linux-kernel - Re: [PATCH 1/3] ftrace: convert unsigned index to signed

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Date:	Tue, 6 Jan 2009 14:50:07 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, fweisbec@...il.com,
	roel.kluin@...il.com, pq@....fi, srostedt@...hat.com
Subject: Re: [PATCH 1/3] ftrace: convert unsigned index to signed

On Tue, 06 Jan 2009 17:33:38 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> From: Steven Rostedt <srostedt@...hat.com>
> 
> Impact: fix to unsigned compared to less than zero
> 
> Roel Kluin pointed out that there is a compare of an unsigned number
> to less than zero. A previous clean up had the unsigned index set
> to -1 for certain cases, but never converted it to signed.
> 
> Frederic Weisbecker noticed that another index is used to compare
> the above index to and it also needs to be converted to signed.
> 
> Reported-by: Roel Kluin <roel.kluin@...il.com>
> Reported-by: Frederic Weisbecker <fweisbec@...il.com>
> Signed-off-by: Steven Rostedt <srostedt@...hat.com>
> ---
>  kernel/trace/ftrace.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 2f32969..3576707 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -289,7 +289,7 @@ static DEFINE_MUTEX(ftrace_regex_lock);
>  
>  struct ftrace_page {
>  	struct ftrace_page	*next;
> -	unsigned long		index;
> +	long			index;

Does that actually need to be a long type?

>  	struct dyn_ftrace	records[];
>  };
>  
> @@ -786,7 +786,7 @@ enum {
>  
>  struct ftrace_iterator {
>  	struct ftrace_page	*pg;
> -	unsigned		idx;
> +	int			idx;

because we have

        if (iter->idx >= iter->pg->index) {

Are 32-bit types actually more efficient than 64-bit types on any
64-bit hardware which we care about?  
--
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