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=-9.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY,USER_AGENT_GIT autolearn=ham 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 34655C2D0DB for ; Mon, 20 Jan 2020 10:05:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0EE082087E for ; Mon, 20 Jan 2020 10:05:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727683AbgATKFg (ORCPT ); Mon, 20 Jan 2020 05:05:36 -0500 Received: from out30-42.freemail.mail.aliyun.com ([115.124.30.42]:57535 "EHLO out30-42.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726075AbgATKFg (ORCPT ); Mon, 20 Jan 2020 05:05:36 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R141e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04394;MF=wenyang@linux.alibaba.com;NM=1;PH=DS;RN=5;SR=0;TI=SMTPD_---0ToDeF5-_1579514727; Received: from localhost(mailfrom:wenyang@linux.alibaba.com fp:SMTPD_---0ToDeF5-_1579514727) by smtp.aliyun-inc.com(127.0.0.1); Mon, 20 Jan 2020 18:05:34 +0800 From: Wen Yang To: John Stultz , Thomas Gleixner Cc: Wen Yang , Stephen Boyd , linux-kernel@vger.kernel.org Subject: [PATCH] timekeeping: improve arithmetic division in scale64_check_overflow() Date: Mon, 20 Jan 2020 18:05:23 +0800 Message-Id: <20200120100523.45656-1-wenyang@linux.alibaba.com> X-Mailer: git-send-email 2.23.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org do_div() does a 64-by-32 division. Use div64_u64() instead of it if the divisor is u64, to avoid truncation to 32-bit. And as a nice side effect also cleans up the function a bit. Signed-off-by: Wen Yang Cc: John Stultz Cc: Thomas Gleixner Cc: Stephen Boyd Cc: linux-kernel@vger.kernel.org --- kernel/time/timekeeping.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index ca69290bee2a..4fc2af4367a7 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -1005,9 +1005,8 @@ static int scale64_check_overflow(u64 mult, u64 div, u64 *base) ((int)sizeof(u64)*8 - fls64(mult) < fls64(rem))) return -EOVERFLOW; tmp *= mult; - rem *= mult; - do_div(rem, div); + rem = div64_u64(rem * mult, div); *base = tmp + rem; return 0; } -- 2.23.0