From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756950AbbJIJqz (ORCPT ); Fri, 9 Oct 2015 05:46:55 -0400 Received: from www.linutronix.de ([62.245.132.108]:36582 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754477AbbJIJqx (ORCPT ); Fri, 9 Oct 2015 05:46:53 -0400 Date: Fri, 9 Oct 2015 10:46:16 +0100 (IST) From: Thomas Gleixner To: Miroslav Lichvar cc: Arnd Bergmann , linux-kernel@vger.kernel.org, y2038@lists.linaro.org, John Stultz , Prarit Bhargava , Richard Cochran Subject: Re: [PATCH] timekeeping: Limit system time to prevent 32-bit time_t overflow In-Reply-To: <20151008093923.GQ5778@localhost> Message-ID: References: <1444224137-32510-1-git-send-email-mlichvar@redhat.com> <5753784.UXVo9jVTVp@wuerfel> <20151008062344.GO5778@localhost> <5836683.t4iPTifntz@wuerfel> <20151008093923.GQ5778@localhost> User-Agent: Alpine 2.11 (DEB 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 8 Oct 2015, Miroslav Lichvar wrote: > On Thu, Oct 08, 2015 at 10:52:05AM +0200, Arnd Bergmann wrote: > > On Thursday 08 October 2015 08:23:44 Miroslav Lichvar wrote: > > > The difference is that with the one-week step the kernel and userspace > > > still agree on the current time and it is always valid from the kernel > > > point of view, absolute timers can be set, etc. > > > > Ok, I can see that as an improvement, but it still seems to give > > a false sense of safety, and I feel we really should not have any code > > rely on this behavior. > > Applications are not allowed to rely on system time being sane? > To me the current behavior looks like the kernel is throwing the > applications off a cliff, while it's the only thing that can fly :). As Arnd said, you are creating a wrong sense of safety. They fall off the cliff with your changes as well. The fall is just different. Think about timeouts, user space overflows of time_t etc. We need to fix all of it, no matter what. Thanks, tglx