From mboxrd@z Thu Jan 1 00:00:00 1970 From: Masami Hiramatsu Date: Mon, 17 Nov 2014 08:23:42 +0000 Subject: Re: [PATCH 1/1] kprobes: Deletion of an unnecessary check before the function call "module_put" Message-Id: <5469B08E.90104@hitachi.com> List-Id: References: <5307CAA2.8060406@users.sourceforge.net> <530A086E.8010901@users.sourceforge.net> <530A72AA.3000601@users.sourceforge.net> <530B5FB6.6010207@users.sourceforge.net> <530C5E18.1020800@users.sourceforge.net> <530CD2C4.4050903@users.sourceforge.net> <530CF8FF.8080600@users.sourceforge.net> <530DD06F.4090703@users.sourceforge.net> <5317A59D.4@users.sourceforge.net> <546899CF.8020808@users.sourceforge.net> In-Reply-To: <546899CF.8020808@users.sourceforge.net> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: SF Markus Elfring Cc: Ananth N Mavinakayanahalli , Anil S Keshavamurthy , "David S. Miller" , linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org, Coccinelle (2014/11/16 21:34), SF Markus Elfring wrote: > From: Markus Elfring > 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 > --- > 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@hitachi.com