From: ebiederm at xmission.com (Eric W. Biederman)
Subject: Setting monotonic time?
Date: Wed, 03 Oct 2018 08:14:25 +0200 [thread overview]
Message-ID: <87in2jo8u6.fsf@xmission.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1810030711520.1435@nanos.tec.linutronix.de> (Thomas Gleixner's message of "Wed, 3 Oct 2018 07:25:35 +0200 (CEST)")
Thomas Gleixner <tglx at linutronix.de> writes:
> 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.
Yep. That sounds right.
Eric
WARNING: multiple messages have this Message-ID (diff)
From: ebiederm@xmission.com (Eric W. Biederman)
Subject: Setting monotonic time?
Date: Wed, 03 Oct 2018 08:14:25 +0200 [thread overview]
Message-ID: <87in2jo8u6.fsf@xmission.com> (raw)
Message-ID: <20181003061425.Nqt1D3tCf_HjmYevUzmIl6xbzLoAh5xYwmNt7Q5aA-Q@z> (raw)
In-Reply-To: <alpine.DEB.2.21.1810030711520.1435@nanos.tec.linutronix.de> (Thomas Gleixner's message of "Wed, 3 Oct 2018 07:25:35 +0200 (CEST)")
Thomas Gleixner <tglx at linutronix.de> writes:
> 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.
Yep. That sounds right.
Eric
next prev parent reply other threads:[~2018-10-03 6:14 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
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 [this message]
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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