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From: Thomas Gleixner <tglx@linutronix.de>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andrey Vagin <avagin@virtuozzo.com>,
	Dmitry Safonov <dima@arista.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Dmitry Safonov <0x7f454c46@gmail.com>,
	Adrian Reber <adrian@lisas.de>, Andy Lutomirski <luto@kernel.org>,
	Christian Brauner <christian.brauner@ubuntu.com>,
	Cyrill Gorcunov <gorcunov@openvz.org>,
	"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
	Jeff Dike <jdike@addtoit.com>, Oleg Nesterov <oleg@redhat.com>,
	Pavel Emelianov <xemul@virtuozzo.com>,
	Shuah Khan <shuah@kernel.org>,
	"containers@lists.linux-foundation.org"
	<containers@lists.linux-foundation.org>,
	"criu@openvz.org" <criu@openvz.org>,
	"linux-api@vger.kernel.org" <linux-api@vger.kernel.org>,
	"x86@kernel.org" <x86@kernel.org>, Alexey Dobriyan <ado>
Subject: Re: [RFC 00/20] ns: Introduce Time Namespace
Date: Thu, 27 Sep 2018 23:41:49 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.21.1809272335430.8118@nanos.tec.linutronix.de> (raw)
In-Reply-To: <alpine.DEB.2.21.1809272247270.8118@nanos.tec.linutronix.de>

On Thu, 27 Sep 2018, Thomas Gleixner wrote:
> Add time skew via NTP/PTP into the picture and you might have to adjust
> timers as well, because you need to guarantee that they are not expiring
> early.
> 
> I haven't looked through Dimitry's patches yet, but I don't see how this
> can work at all without introducing subtle issues all over the place.

And just a quick scan tells me that this is broken. Timers will expire
early or late. The latter is acceptible to some extent, but larger delays
might come with surprise. Expiring early is an absolute nono.

Thanks,

	tglx

  reply	other threads:[~2018-09-27 21:41 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-19 20:50 [RFC 00/20] ns: Introduce Time Namespace Dmitry Safonov
2018-09-19 20:50 ` [RFC 01/20] " Dmitry Safonov
2018-09-28 18:20   ` Laurent Vivier
2018-09-19 20:50 ` [RFC 02/20] timens: Add timens_offsets Dmitry Safonov
2018-09-20 18:45   ` Cyrill Gorcunov
2018-09-20 22:14     ` Cyrill Gorcunov
2018-09-19 20:50 ` [RFC 03/20] timens: Introduce CLOCK_MONOTONIC offsets Dmitry Safonov
2018-09-19 20:50 ` [RFC 04/20] timens: Introduce CLOCK_BOOTTIME offset Dmitry Safonov
2018-09-30  3:18   ` [LKP] [timens] 3cc8de9dcb: RIP:posix_get_boottime kernel test robot
2018-09-19 20:50 ` [RFC 05/20] timerfd/timens: Take into account ns clock offsets Dmitry Safonov
2018-09-19 20:50 ` [RFC 06/20] kernel: Take into account timens clock offsets in clock_nanosleep Dmitry Safonov
2018-09-19 20:50 ` [RFC 07/20] timens: Shift /proc/uptime Dmitry Safonov
2018-09-19 20:50 ` [RFC 08/20] x86/vdso: Restrict splitting vvar vma Dmitry Safonov
2018-09-19 20:50 ` [RFC 09/20] x86/vdso/timens: Add offsets page in vvar Dmitry Safonov
2018-09-19 20:50 ` [RFC 10/20] x86/vdso: Use set_normalized_timespec() to avoid 32 bit overflow Dmitry Safonov
2018-09-19 20:50 ` [RFC 11/20] x86/vdso: Purge timens page on setns()/unshare()/clone() Dmitry Safonov
2018-09-19 20:50 ` [RFC 12/20] x86/vdso: Look for vvar vma to purge timens page Dmitry Safonov
2018-09-19 20:50 ` [RFC 13/20] posix-timers/timens: Take into account clock offsets Dmitry Safonov
2018-09-30  3:11   ` [LKP] [posix] 25217c6e39: BUG:KASAN:null-ptr-deref_in_c kernel test robot
2018-09-19 20:50 ` [RFC 14/20] timens: Add align for timens_offsets Dmitry Safonov
2018-09-19 20:50 ` [RFC 15/20] timens: Optimize zero-offsets Dmitry Safonov
2018-09-19 20:50 ` [RFC 16/20] selftest: Add Time Namespace test for supported clocks Dmitry Safonov
2018-09-24 21:36   ` Shuah Khan
2018-09-19 20:50 ` [RFC 17/20] selftest/timens: Add test for timerfd Dmitry Safonov
2018-09-19 20:50 ` [RFC 18/20] selftest/timens: Add test for clock_nanosleep Dmitry Safonov
2018-09-19 20:50 ` [RFC 19/20] timens/selftest: Add procfs selftest Dmitry Safonov
2018-09-19 20:50 ` [RFC 20/20] timens/selftest: Add timer offsets test Dmitry Safonov
2018-09-21 12:27 ` [RFC 00/20] ns: Introduce Time Namespace Eric W. Biederman
2018-09-24 20:51   ` Andrey Vagin
2018-09-24 22:02     ` Eric W. Biederman
2018-09-25  1:42       ` Andrey Vagin
2018-09-26 17:36         ` Eric W. Biederman
2018-09-26 17:59           ` Dmitry Safonov
2018-09-27 21:30           ` Thomas Gleixner
2018-09-27 21:41             ` Thomas Gleixner [this message]
2018-10-01 23:20               ` Andrey Vagin
2018-10-02  6:15                 ` Thomas Gleixner
2018-10-02 21:05                   ` Dmitry Safonov
2018-10-02 21:26                     ` Thomas Gleixner
2018-09-28 17:03             ` Eric W. Biederman
2018-09-28 19:32               ` Thomas Gleixner
2018-10-01  9:05                 ` Eric W. Biederman
2018-10-01  9:15                 ` Setting monotonic time? Eric W. Biederman
2018-10-01 18:52                   ` Thomas Gleixner
2018-10-02 20:00                     ` Arnd Bergmann
2018-10-02 20:06                       ` Thomas Gleixner
2018-10-03  4:50                         ` Eric W. Biederman
2018-10-03  5:25                           ` Thomas Gleixner
2018-10-03  6:14                             ` Eric W. Biederman
2018-10-03  7:02                               ` Arnd Bergmann
2018-10-03  6:14                             ` Thomas Gleixner
2018-10-01 20:51                   ` Andrey Vagin
2018-10-02  6:16                     ` Thomas Gleixner
2018-10-21  1:41               ` [RFC 00/20] ns: Introduce Time Namespace Andrei Vagin
2018-10-21  3:54                 ` Andrei Vagin
2018-10-29 20:33                 ` Thomas Gleixner
2018-10-29 21:21                   ` Eric W. Biederman
2018-10-29 21:36                     ` Thomas Gleixner
2018-10-31 16:26                   ` Andrei Vagin

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