linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Thomas Gleixner <tglx@linutronix.de>
To: "Pali Rohár" <pali@kernel.org>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Missing CLOCK_BOOTTIME_RAW?
Date: Mon, 18 May 2020 13:26:14 +0200	[thread overview]
Message-ID: <87ftbxxz55.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20200518111103.sj73h5j3r75zv2wp@pali>

Pali Rohár <pali@kernel.org> writes:
> On Saturday 09 May 2020 11:49:27 Thomas Gleixner wrote:
>> Sure, but what's the problem? The adjustemt is done to make the observed
>> time as correct as possible.
>
> Yes. But correction may take lot of time, e.g. also more then one day.
>
> So during this period when correction is in progress, measuring time
> difference via CLOCK_MONITONIC will have incorrect results.
>
> It already happened for me, system clock was shifted by one hour and
> chronyd started adjustment, it slow down system clock. 6 real hours
> passed and via system clock was measured time difference only about
> 5 hours and 20 minutes (correction was still in progress as system
> clock at that time was still shifted by about 20 minutes).

System clock shifted by one hour? You mean DST change? If chronyd
adjusts that by smoothing the frequency, that's just broken and really
not the kernel's problem.

Thanks,

        tglx

  reply	other threads:[~2020-05-18 11:26 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-08 20:18 Missing CLOCK_BOOTTIME_RAW? Pali Rohár
2020-05-08 20:59 ` Thomas Gleixner
2020-05-08 21:31   ` Pali Rohár
2020-05-09  9:49     ` Thomas Gleixner
2020-05-18 11:11       ` Pali Rohár
2020-05-18 11:26         ` Thomas Gleixner [this message]
2020-05-18 11:35           ` Pali Rohár
2020-05-18 12:13             ` Thomas Gleixner
2020-05-18 12:49               ` Pali Rohár
2020-05-18 13:01                 ` Thomas Gleixner

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=87ftbxxz55.fsf@nanos.tec.linutronix.de \
    --to=tglx@linutronix.de \
    --cc=linux-kernel@vger.kernel.org \
    --cc=pali@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).