From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754366AbcBVQme (ORCPT ); Mon, 22 Feb 2016 11:42:34 -0500 Received: from mail-qk0-f179.google.com ([209.85.220.179]:34105 "EHLO mail-qk0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752828AbcBVQmb (ORCPT ); Mon, 22 Feb 2016 11:42:31 -0500 Subject: Re: [PATCH] rtc: Add an option to invalidate dates in 2038 To: Arnd Bergmann , Alexandre Belloni References: <1455995444-14146-1-git-send-email-alexandre.belloni@free-electrons.com> <6269543.oe8MmZQUmX@wuerfel> <20160222155653.GP2222@piout.net> <2768647.1bFEcFDZRI@wuerfel> Cc: One Thousand Gnomes , rtc-linux@googlegroups.com, Alessandro Zummo , Willy Tarreau , linux-kernel@vger.kernel.org From: "Austin S. Hemmelgarn" Message-ID: <56CB3A1D.6030604@gmail.com> Date: Mon, 22 Feb 2016 11:41:01 -0500 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: <2768647.1bFEcFDZRI@wuerfel> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Antivirus: avast! (VPS 160222-0, 2016-02-22), Outbound message X-Antivirus-Status: Clean Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2016-02-22 11:18, Arnd Bergmann wrote: > On Monday 22 February 2016 16:56:53 Alexandre Belloni wrote: >> One other workaround is to asked distributions >> using systemd to stop using HCTOSYS so userspace would be responsible to >> set the system time and in that case we won't have the 32/64 discrepancy. > > I'm missing a bit of background here. This seems like a fairly useful > piece of infrastructure for the majority of the use cases (working RTC) > > How would the time get set when this is disabled? Is systemd able > to read the rtc and write it back to the kernel? That could in fact > be a nicer workaround for the problem, if it just does this before > setting up the timerfd. Traditional init systems on Linux have the option of using hwclock from util-linux to set the system time. This is what Gentoo does by default, and I think Arch does it too, and I'm relatively certain that Debian and Ubuntu used to do it before they switched to systemd (I have no idea what they do now). Based on the manpage for hwclock, it looks like systemd mandates that HCTOSYS is enabled in the kernel configuration, and then just calls hwclock to set the system timezone and correct for UTC.