Re: hwclock's synchronize_to_clock_tick_rtc returns inconsistent values

[J William Piggott <elseifthen@gmx.com>]

On 04/16/2015 04:36 PM, Andreas Henriksson wrote:
> Hello!
> 
> The below forwarded issue seems to have been introduced in
> commit ab8f402952301106ad0bd5c5a51dc
> "hwclock: don't confuse users with select() timeout warning"
> 
> This issue is also tracked at http://bugs.debian.org/782726
> 
> Regards,
> Andreas Henriksson
> 
> ----- Forwarded message from Serge Schneider <serge@raspberrypi.org> -----
> 
> Date: Thu, 16 Apr 2015 20:24:26 +0100
> From: Serge Schneider <serge@raspberrypi.org>
> To: submit@bugs.debian.org
> Subject: Bug#782726: util-linux: hwclock's synchronize_to_clock_tick_rtc
> 	returns inconsistent values
> User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101
> 	Thunderbird/31.6.0
> 
> Package: util-linux
> Version: 2.25.2-6
> Severity: normal
> 
> Dear Maintainer,
>                         rc = select(rtc_fd + 1, &rfds, NULL, NULL, &tv);
>                         ret = 1;
>                         if (rc == -1)
>                                 warn(_("select() to %s to wait for clock tick
> failed"),
>                                      rtc_dev_name);
>                         else if (rc == 0 && debug)
>                                 printf(_("select() to %s to wait for clock
> tick timed out"),
>                                      rtc_dev_name);
>                         else
>                                 ret = 0;
>

Karel,

The select time out still needs to return 1, so the debug test should
have been a separate statement.

I don't have time to patch and test this right now, but I can do it
later if you want?


> When 'select' times out and returns 0, synchronize_to_clock_tick_rtc returns
> either 1 or 0, depnding on whether the -D option (debug) was used. This causes
> hwclock -r to succeed and hwclock -r -D to return an error. In one case, it
> just fails, in the other, the values are off by the timeout period (10
> seconds, in this version).
> 
> pi@test-pi ~/dev/util-linux-2.25.2 $ sudo ./hwclock -r
> Thu 16 Apr 2015 19:18:44 UTC  -10.016913 seconds
> pi@test-pi ~/dev/util-linux-2.25.2 $ sudo ./hwclock -r -D
> hwclock from util-linux 2.25.2
> Using the /dev interface to the clock.
> Last drift adjustment done at 1429205484 seconds after 1969
> Last calibration done at 1429205484 seconds after 1969
> Hardware clock is on UTC time
> Assuming hardware clock is kept in UTC time.
> Waiting for clock tick...
> select() to /dev/rtc0 to wait for clock tick timed out...synchronization
> failed
> 
> ----- End forwarded message -----
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