From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Sun, 01 Jul 2018 18:26:55 +0200 (CEST) Received: from mail.linuxfoundation.org ([140.211.169.12]:52672 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by eddie.linux-mips.org with ESMTP id S23993339AbeGAQ0cixnWh (ORCPT ); Sun, 1 Jul 2018 18:26:32 +0200 Received: from localhost (LFbn-1-12247-202.w90-92.abo.wanadoo.fr [90.92.61.202]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 19489AF8; Sun, 1 Jul 2018 16:26:25 +0000 (UTC) From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Geert Uytterhoeven , Thomas Gleixner , Arnd Bergmann , John Stultz , Stephen Boyd , linux-alpha@vger.kernel.org, linux-mips@linux-mips.org Subject: [PATCH 4.9 051/101] time: Make sure jiffies_to_msecs() preserves non-zero time periods Date: Sun, 1 Jul 2018 18:21:37 +0200 Message-Id: <20180701160759.191741833@linuxfoundation.org> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20180701160757.138608453@linuxfoundation.org> References: <20180701160757.138608453@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 64527 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: gregkh@linuxfoundation.org Precedence: bulk List-help: List-unsubscribe: List-software: Ecartis version 1.0.0 List-Id: linux-mips X-List-ID: linux-mips List-subscribe: List-owner: List-post: List-archive: X-list: linux-mips 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Geert Uytterhoeven commit abcbcb80cd09cd40f2089d912764e315459b71f7 upstream. 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 Signed-off-by: Greg Kroah-Hartman --- kernel/time/time.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/kernel/time/time.c +++ b/kernel/time/time.c @@ -28,6 +28,7 @@ */ #include +#include #include #include #include @@ -258,9 +259,10 @@ unsigned int jiffies_to_msecs(const unsi 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 }