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From: Thomas Gleixner <tglx@linutronix.de>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
	avagin@virtuozzo.com, dima@arista.com,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	0x7f454c46@gmail.com, adrian@lisas.de,
	Andy Lutomirski <luto@kernel.org>,
	Christian Brauner <christian.brauner@ubuntu.com>,
	gorcunov@openvz.org, "H. Peter Anvin" <hpa@zytor.com>,
	Ingo Molnar <mingo@redhat.com>, Jeff Dike <jdike@addtoit.com>,
	Oleg Nesterov <oleg@redhat.com>,
	xemul@virtuozzo.com, Shuah Khan <shuah@kernel.org>,
	containers@lists.linux-foundation.org, criu@openvz.org,
	Linux API <linux-api@vger.kernel.org>,
	the arch/x86 maintainers <x86@kernel.org>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	linux-kselftest@vger.kernel.org
Subject: Re: Setting monotonic time?
Date: Wed, 3 Oct 2018 07:25:35 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.21.1810030711520.1435@nanos.tec.linutronix.de> (raw)
In-Reply-To: <87in2jskew.fsf@xmission.com>

On Wed, 3 Oct 2018, Eric W. Biederman wrote:
> Direct access to hardware/drivers and not through an abstraction like
> the vfs (an abstraction over block devices) can legitimately be handled
> by hotplug events.  I unplug one keyboard I plug in another.
> 
> I don't know if the input layer is more of a general abstraction
> or more of a hardware device.  I have not dug into it but my guess
> is abstraction from what I have heard.
> 
> The scary difficulty here is if after restart input is reporting times
> in CLOCK_MONOTONIC and the applications in the namespace are talking
> about times in CLOCK_MONOTONIC_SYNC.  Then there is an issue.  As even
> with a fixed offset the times don't match up.
> 
> So a time namespace absolutely needs to do is figure out how to deal
> with all of the kernel interfaces reporting times and figure out how to
> report them in the current time namespace.

So you want to talk to Arnd who is leading the y2038 effort. He knowns how
many and which interfaces are involved aside of the obvious core timer
ones. It's quite an amount and the problem is that you really need to do
that at the interface level, because many of those time stamps are taken in
contexts which are completely oblivious of name spaces. Ditto for timeouts
and similar things which are handed in through these interfaces.

Thanks,

	tglx

  reply	other threads:[~2018-10-03  5:25 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
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 [this message]
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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