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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 181B1C43144 for ; Fri, 22 Jun 2018 15:52:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C043224555 for ; Fri, 22 Jun 2018 15:52:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C043224555 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zytor.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934039AbeFVPwG (ORCPT ); Fri, 22 Jun 2018 11:52:06 -0400 Received: from terminus.zytor.com ([198.137.202.136]:41063 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934003AbeFVPwE (ORCPT ); Fri, 22 Jun 2018 11:52:04 -0400 Received: from terminus.zytor.com (localhost [127.0.0.1]) by terminus.zytor.com (8.15.2/8.15.2) with ESMTPS id w5MFprMw125336 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Fri, 22 Jun 2018 08:51:53 -0700 Received: (from tipbot@localhost) by terminus.zytor.com (8.15.2/8.15.2/Submit) id w5MFpqR6125333; Fri, 22 Jun 2018 08:51:52 -0700 Date: Fri, 22 Jun 2018 08:51:52 -0700 X-Authentication-Warning: terminus.zytor.com: tipbot set sender to tipbot@zytor.com using -f From: tip-bot for Geert Uytterhoeven Message-ID: Cc: arnd@arndb.de, john.stultz@linaro.org, geert@linux-m68k.org, sboyd@kernel.org, tglx@linutronix.de, linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org Reply-To: john.stultz@linaro.org, arnd@arndb.de, mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, tglx@linutronix.de, sboyd@kernel.org, geert@linux-m68k.org In-Reply-To: <20180622143357.7495-1-geert@linux-m68k.org> References: <20180622143357.7495-1-geert@linux-m68k.org> To: linux-tip-commits@vger.kernel.org Subject: [tip:timers/urgent] time: Make sure jiffies_to_msecs() preserves non-zero time periods Git-Commit-ID: abcbcb80cd09cd40f2089d912764e315459b71f7 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: abcbcb80cd09cd40f2089d912764e315459b71f7 Gitweb: https://git.kernel.org/tip/abcbcb80cd09cd40f2089d912764e315459b71f7 Author: Geert Uytterhoeven AuthorDate: Fri, 22 Jun 2018 16:33:57 +0200 Committer: Thomas Gleixner CommitDate: Fri, 22 Jun 2018 17:48:36 +0200 time: Make sure jiffies_to_msecs() preserves non-zero time periods For the common cases where 1000 is a multiple of HZ, or HZ is a multiple of 1000, jiffies_to_msecs() never returns zero when passed a non-zero time period. However, if HZ > 1000 and not an integer multiple of 1000 (e.g. 1024 or 1200, as used on alpha and DECstation), jiffies_to_msecs() may return zero for small non-zero time periods. This may break code that relies on receiving back a non-zero value. jiffies_to_usecs() does not need such a fix: one jiffy can only be less than one µs if HZ > 1000000, and such large values of HZ are already rejected at build time, twice: - include/linux/jiffies.h does #error if HZ >= 12288, - kernel/time/time.c has BUILD_BUG_ON(HZ > USEC_PER_SEC). Broken since forever. Signed-off-by: Geert Uytterhoeven Signed-off-by: Thomas Gleixner Reviewed-by: Arnd Bergmann Cc: John Stultz Cc: Stephen Boyd Cc: linux-alpha@vger.kernel.org Cc: linux-mips@linux-mips.org Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20180622143357.7495-1-geert@linux-m68k.org --- kernel/time/time.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/time/time.c b/kernel/time/time.c index 6fa99213fc72..2b41e8e2d31d 100644 --- a/kernel/time/time.c +++ b/kernel/time/time.c @@ -28,6 +28,7 @@ */ #include +#include #include #include #include @@ -314,9 +315,10 @@ unsigned int jiffies_to_msecs(const unsigned long j) return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC); #else # if BITS_PER_LONG == 32 - return (HZ_TO_MSEC_MUL32 * j) >> HZ_TO_MSEC_SHR32; + return (HZ_TO_MSEC_MUL32 * j + (1ULL << HZ_TO_MSEC_SHR32) - 1) >> + HZ_TO_MSEC_SHR32; # else - return (j * HZ_TO_MSEC_NUM) / HZ_TO_MSEC_DEN; + return DIV_ROUND_UP(j * HZ_TO_MSEC_NUM, HZ_TO_MSEC_DEN); # endif #endif }