From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 02A2AC2D0C2 for ; Fri, 3 Jan 2020 11:31:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D34BC21835 for ; Fri, 3 Jan 2020 11:31:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727589AbgACLbx (ORCPT ); Fri, 3 Jan 2020 06:31:53 -0500 Received: from out30-56.freemail.mail.aliyun.com ([115.124.30.56]:41083 "EHLO out30-56.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727453AbgACLbx (ORCPT ); Fri, 3 Jan 2020 06:31:53 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R821e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e07487;MF=wenyang@linux.alibaba.com;NM=1;PH=DS;RN=5;SR=0;TI=SMTPD_---0TmjiLWd_1578051110; Received: from IT-C02W23QPG8WN.local(mailfrom:wenyang@linux.alibaba.com fp:SMTPD_---0TmjiLWd_1578051110) by smtp.aliyun-inc.com(127.0.0.1); Fri, 03 Jan 2020 19:31:51 +0800 Subject: Re: [PATCH v2] ftrace: avoid potential division by zero To: Justin Capella Cc: Steven Rostedt , Ingo Molnar , xlpang@linux.alibaba.com, LKML References: <20200103030248.14516-1-wenyang@linux.alibaba.com> From: Wen Yang Message-ID: Date: Fri, 3 Jan 2020 19:31:49 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/1/3 4:00 下午, Justin Capella wrote: >> - do_div(stddev, rec->counter * (rec->counter - 1) * 1000); >> >> + stddev = div64_ul(stddev, >> + rec->counter * (rec->counter - 1) * 1000); > > > Is a rec->counter > 1 assertion needed here? > Hello, the above lines deal with this situation: if (rec->counter <= 1) stddev = 0; else { -- Regards, Wen