From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755599AbaKTDxw (ORCPT ); Wed, 19 Nov 2014 22:53:52 -0500 Received: from mail9.hitachi.co.jp ([133.145.228.44]:58690 "EHLO mail9.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753718AbaKTDxv (ORCPT ); Wed, 19 Nov 2014 22:53:51 -0500 Message-ID: <546D65C6.3030109@hitachi.com> Date: Thu, 20 Nov 2014 12:53:42 +0900 From: Masami Hiramatsu Organization: Hitachi, Ltd., Japan User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:13.0) Gecko/20120614 Thunderbird/13.0.1 MIME-Version: 1.0 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 Subject: Re: [PATCH 1/1] kprobes: Deletion of an unnecessary check before the function call "module_put" 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> <5469B08E.90104@hitachi.com> <546C41EF.4040502@users.sourceforge.net> In-Reply-To: <546C41EF.4040502@users.sourceforge.net> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (2014/11/19 16:08), SF Markus Elfring wrote: >>> 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(). > > Do you want that I replace the shown null pointer check by a short > comment which repeats an expectation for the affected function call? No, not "want". IMHO, if try_module_get(mod) is done only when mod!=NULL, we shouldn't call module_put(mod) when mod==NULL (even if it is possible), because those get/put method must be used as a pair, for the better understandings. Thank you, -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com From mboxrd@z Thu Jan 1 00:00:00 1970 From: Masami Hiramatsu Date: Thu, 20 Nov 2014 03:53:42 +0000 Subject: Re: [PATCH 1/1] kprobes: Deletion of an unnecessary check before the function call "module_put" Message-Id: <546D65C6.3030109@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> <5469B08E.90104@hitachi.com> <546C41EF.4040502@users.sourceforge.net> In-Reply-To: <546C41EF.4040502@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 (2014/11/19 16:08), SF Markus Elfring wrote: >>> 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(). > > Do you want that I replace the shown null pointer check by a short > comment which repeats an expectation for the affected function call? No, not "want". IMHO, if try_module_get(mod) is done only when mod!=NULL, we shouldn't call module_put(mod) when mod=NULL (even if it is possible), because those get/put method must be used as a pair, for the better understandings. Thank you, -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com