linux-kernel - Re: [bugreport] "hwclock -w" reset time instead of setting the right time

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Message-ID: <20200102131434.tky2hquki23laqqo@10.255.255.10>
Date:   Thu, 2 Jan 2020 14:14:34 +0100
From:   Karel Zak <kzak@...hat.com>
To:     Mikhail Gavrilov <mikhail.v.gavrilov@...il.com>
Cc:     util-linux@...r.kernel.org,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        linux-rtc@...r.kernel.org
Subject: Re: [bugreport] "hwclock -w" reset time instead of setting the right
 time

On Thu, Jan 02, 2020 at 04:55:32PM +0500, Mikhail Gavrilov wrote:
> # hwclock -w -v
> hwclock from util-linux 2.35-rc1-20-63f8
> System Time: 1577964536.796672
> Trying to open: /dev/rtc0
> Using the rtc interface to the clock.
> Last drift adjustment done at 1577950892 seconds after 1969
> Last calibration done at 1577950892 seconds after 1969
> Hardware clock is on UTC time
> Assuming hardware clock is kept in UTC time.
> RTC type: 'rtc_cmos'
> Using delay: 0.500000 seconds
> missed it - 1577964536.797135 is too far past 1577964536.500000
> (0.297135 > 0.001000)
> 1577964537.500000 is close enough to 1577964537.500000 (0.000000 < 0.002000)
> Set RTC to 1577964537 (1577964536 + 1; refsystime = 1577964536.000000)
> Setting Hardware Clock to 11:28:57 = 1577964537 seconds since 1969
> ioctl(RTC_SET_TIME) was successful.
> Not adjusting drift factor because the --update-drift option was not used.
> New /etc/adjtime data:
> 0.000000 1577964536 0.000000
> 1577964536
> UTC

At first glance it seems hwclock works as expected, I do not see
anything wrong in the output.

> Demonstration: https://youtu.be/Yx27IH2opEc

What is hw time before reboot? Can you verify that hwclock reset the
clock? (or is it system reboot?)

    # hwclock -w -v
    # hwclock -v

Do you see anything interesting in dmesg output before reboot and after
hwclock -w? 


(CC: to linux-rtc@...r.kernel.org).

    Karel

-- 
 Karel Zak  <kzak@...hat.com>
 http://karelzak.blogspot.com