From: tglx@linutronix.de (Thomas Gleixner)
Subject: [RFC 00/20] ns: Introduce Time Namespace
Date: Tue, 2 Oct 2018 08:15:15 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.21.1810020811290.32062@nanos.tec.linutronix.de> (raw)
Message-ID: <20181002061515.vafY68aWhVg05gINowyCLCf-f8J9snTWzJ0MvY9nHf0@z> (raw)
In-Reply-To: <20181001232033.GA31324@outlook.office365.com>
On Mon, 1 Oct 2018, Andrey Vagin wrote:
> On Thu, Sep 27, 2018@11:41:49PM +0200, Thomas Gleixner wrote:
> > 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.
>
> Do you mean that we have to adjust all timers after changing offset for
> CLOCK_MONOTONIC or CLOCK_BOOTTIME? Our idea is that offsets for
> monotonic and boot times will be set immediately after creating a time
> namespace before using any timers.
I explained that in detail in this thread, but it's not about the initial
setting of clock mono/boot before any timers have been armed.
It's about setting the offset or clock realtime (via settimeofday) when
timers are already armed. Also having a entirely different time domain,
e.g. separate NTP adjustments, makes that necessary.
Thanks,
tglx
next prev parent reply other threads:[~2018-10-02 6:15 UTC|newest]
Thread overview: 78+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-19 20:50 [RFC 00/20] ns: Introduce Time Namespace dima
2018-09-19 20:50 ` Dmitry Safonov
2018-09-19 20:50 ` [RFC 16/20] selftest: Add Time Namespace test for supported clocks dima
2018-09-19 20:50 ` Dmitry Safonov
2018-09-24 21:36 ` shuah
2018-09-24 21:36 ` Shuah Khan
2018-09-19 20:50 ` [RFC 17/20] selftest/timens: Add test for timerfd dima
2018-09-19 20:50 ` Dmitry Safonov
2018-09-19 20:50 ` [RFC 18/20] selftest/timens: Add test for clock_nanosleep dima
2018-09-19 20:50 ` Dmitry Safonov
2018-09-19 20:50 ` [RFC 19/20] timens/selftest: Add procfs selftest dima
2018-09-19 20:50 ` Dmitry Safonov
2018-09-19 20:50 ` [RFC 20/20] timens/selftest: Add timer offsets test dima
2018-09-19 20:50 ` Dmitry Safonov
2018-09-21 12:27 ` [RFC 00/20] ns: Introduce Time Namespace ebiederm
2018-09-21 12:27 ` Eric W. Biederman
2018-09-24 20:51 ` avagin
2018-09-24 20:51 ` Andrey Vagin
2018-09-24 22:02 ` ebiederm
2018-09-24 22:02 ` Eric W. Biederman
2018-09-25 1:42 ` avagin
2018-09-25 1:42 ` Andrey Vagin
2018-09-26 17:36 ` ebiederm
2018-09-26 17:36 ` Eric W. Biederman
2018-09-26 17:59 ` 0x7f454c46
2018-09-26 17:59 ` Dmitry Safonov
2018-09-27 21:30 ` tglx
2018-09-27 21:30 ` Thomas Gleixner
2018-09-27 21:41 ` tglx
2018-09-27 21:41 ` Thomas Gleixner
2018-10-01 23:20 ` avagin
2018-10-01 23:20 ` Andrey Vagin
2018-10-02 6:15 ` tglx [this message]
2018-10-02 6:15 ` Thomas Gleixner
2018-10-02 21:05 ` 0x7f454c46
2018-10-02 21:05 ` Dmitry Safonov
2018-10-02 21:26 ` tglx
2018-10-02 21:26 ` Thomas Gleixner
2018-09-28 17:03 ` ebiederm
2018-09-28 17:03 ` Eric W. Biederman
2018-09-28 19:32 ` tglx
2018-09-28 19:32 ` Thomas Gleixner
2018-10-01 9:05 ` ebiederm
2018-10-01 9:05 ` Eric W. Biederman
2018-10-01 9:15 ` Setting monotonic time? ebiederm
2018-10-01 9:15 ` Eric W. Biederman
2018-10-01 18:52 ` tglx
2018-10-01 18:52 ` Thomas Gleixner
2018-10-02 20:00 ` arnd
2018-10-02 20:00 ` Arnd Bergmann
2018-10-02 20:06 ` tglx
2018-10-02 20:06 ` Thomas Gleixner
2018-10-03 4:50 ` ebiederm
2018-10-03 4:50 ` Eric W. Biederman
2018-10-03 5:25 ` tglx
2018-10-03 5:25 ` Thomas Gleixner
2018-10-03 6:14 ` ebiederm
2018-10-03 6:14 ` Eric W. Biederman
2018-10-03 7:02 ` arnd
2018-10-03 7:02 ` Arnd Bergmann
2018-10-03 6:14 ` tglx
2018-10-03 6:14 ` Thomas Gleixner
2018-10-01 20:51 ` avagin
2018-10-01 20:51 ` Andrey Vagin
2018-10-02 6:16 ` tglx
2018-10-02 6:16 ` Thomas Gleixner
2018-10-21 1:41 ` [RFC 00/20] ns: Introduce Time Namespace avagin
2018-10-21 1:41 ` Andrei Vagin
2018-10-21 3:54 ` avagin
2018-10-21 3:54 ` Andrei Vagin
2018-10-29 20:33 ` tglx
2018-10-29 20:33 ` Thomas Gleixner
2018-10-29 21:21 ` ebiederm
2018-10-29 21:21 ` Eric W. Biederman
2018-10-29 21:36 ` tglx
2018-10-29 21:36 ` Thomas Gleixner
2018-10-31 16:26 ` avagin
2018-10-31 16:26 ` Andrei Vagin
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