linux-kernel - Re: [PATCH 1/1] kprobes: Deletion of an unnecessary check before the function call "module

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Date:	Mon, 17 Nov 2014 17:23:42 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	SF Markus Elfring <elfring@...rs.sourceforge.net>
Cc:	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
	"David S. Miller" <davem@...emloft.net>,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
	Coccinelle <cocci@...teme.lip6.fr>
Subject: Re: [PATCH 1/1] kprobes: Deletion of an unnecessary check before
 the function call "module_put"

(2014/11/16 21:34), SF Markus Elfring wrote:
> From: Markus Elfring <elfring@...rs.sourceforge.net>
> Date: Sun, 16 Nov 2014 12:20:31 +0100
> 
> The module_put() function tests whether its argument is NULL and then
> returns immediately. Thus the test around the call is not needed.
> 
> This issue was detected by using the Coccinelle software.
> 
> Signed-off-by: Markus Elfring <elfring@...rs.sourceforge.net>
> ---
>  kernel/kprobes.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 3995f54..f1e7d45 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -1527,8 +1527,7 @@ int register_kprobe(struct kprobe *p)
>  out:
>  	mutex_unlock(&kprobe_mutex);
>  
> -	if (probed_mod)
> -		module_put(probed_mod);
> +	module_put(probed_mod);

This is OK, but I you request a comment line over there so that
code reader can understand it is safe to pass a NULL pointer to
module_put().

# and of course don't touch jump label around that :)

Thank you,

>  
>  	return ret;
>  }
> 


-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com


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