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=-3.7 required=3.0 tests=BAYES_00, 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 A70D5C4363A for ; Fri, 30 Oct 2020 13:57:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5AD5D2076E for ; Fri, 30 Oct 2020 13:57:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726740AbgJ3N5n (ORCPT ); Fri, 30 Oct 2020 09:57:43 -0400 Received: from mx2.suse.de ([195.135.220.15]:53856 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725939AbgJ3N5k (ORCPT ); Fri, 30 Oct 2020 09:57:40 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 95BF6ACAE; Fri, 30 Oct 2020 13:57:39 +0000 (UTC) Date: Fri, 30 Oct 2020 14:58:16 +0100 From: Cyril Hrubis To: Lukasz Majewski Cc: Andrei Vagin , Dmitry Safonov , Thomas Gleixner , GNU C Library , linux-kernel@vger.kernel.org Subject: Re: [Y2038][time namespaces] Question regarding CLOCK_REALTIME support plans in Linux time namespaces Message-ID: <20201030135816.GA1790@yuki.lan> References: <20201030110229.43f0773b@jawa> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201030110229.43f0773b@jawa> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi! > I do have a question regarding the Linux time namespaces in respect of > adding support for virtualizing the CLOCK_REALTIME. > > According to patch description [1] and time_namespaces documentation > [2] the CLOCK_REALTIME is not supported (for now?) to avoid complexity > and overhead in the kernel. > > Is there any plan to add support for it in a near future? > > Why I'm asking? > > It looks like this kernel feature (with CLOCK_REALTIME support > available) would be very helpful for testing Y2038 compliance for e.g. > glibc 32 bit ports. > > To be more specific - it would be possible to modify time after time_t > 32 bit overflow (i.e. Y2038 bug) on the process running Y2038 > regression tests on the host system (64 bit one). By using Linux time > namespaces the system time will not be affected in any way. And what's exactly wrong with moving the system time forward for a duration of the test? -- Cyril Hrubis chrubis@suse.cz