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_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 24229C433FF for ; Wed, 14 Aug 2019 09:17:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ECC0A20843 for ; Wed, 14 Aug 2019 09:17:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726500AbfHNJRs (ORCPT ); Wed, 14 Aug 2019 05:17:48 -0400 Received: from gardel.0pointer.net ([85.214.157.71]:34924 "EHLO gardel.0pointer.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725861AbfHNJRr (ORCPT ); Wed, 14 Aug 2019 05:17:47 -0400 X-Greylist: delayed 489 seconds by postgrey-1.27 at vger.kernel.org; Wed, 14 Aug 2019 05:17:47 EDT Received: from gardel-login.0pointer.net (gardel.0pointer.net [85.214.157.71]) by gardel.0pointer.net (Postfix) with ESMTP id EF34CE80937; Wed, 14 Aug 2019 11:09:36 +0200 (CEST) Received: by gardel-login.0pointer.net (Postfix, from userid 1000) id 950C2160102; Wed, 14 Aug 2019 11:09:36 +0200 (CEST) Date: Wed, 14 Aug 2019 11:09:36 +0200 From: Lennart Poettering To: Arnd Bergmann Cc: "Theodore Y. Ts'o" , Linus Torvalds , Linux Kernel Mailing List , Thomas Gleixner , John Stultz , Alexandre Belloni , Stephen Boyd , Florian Weimer , "H. Peter Anvin" , Palmer Dabbelt , Alistair Francis , GNU C Library , Karel Zak , OGAWA Hirofumi Subject: Re: New kernel interface for sys_tz and timewarp? Message-ID: <20190814090936.GB10516@gardel-login> References: <20190814000622.GB20365@mit.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mi, 14.08.19 10:31, Arnd Bergmann (arnd@arndb.de) wrote: > - glibc stops passing the caller timezone argument to the kernel > - the distro kernel disables CONFIG_RTC_HCTOSYS, > CONFIG_RTC_SYSTOHC and CONFIG_GENERIC_CMOS_UPDATE What's the benefit of letting userspace do this? It sounds a lot more fragile to leave this syncing to userspace if the kernel can do this trivially on its own. IIRC there are uses in kernel that use CLOCK_REALTIME already before userspace starts. e.g. iirc networking generally prefers CLOCK_REALTIME timestamps over CLOCK_MONOTONIC timestamps (i.e. SO_TIMESTAMP and friends are still CLOCK_REALTIME only so far, unless I am missing something). If the kernel comes up with a CLOCK_REALTIME that starts at 0 this is pretty annoying I figure... Hence, so far I suggested to distros to continue turning on the options above, and let the kernel do this on its own without involving userspace in that. Lennart -- Lennart Poettering, Berlin