Re: [chrony-dev] Re: Are there known issues in destructive tests on arm64 or ppc64

[Vincent Blut <vincent.debian@xxxxxxx>]

Hi,

On 2019-12-09T12:00+0100, Christian Ehrhardt wrote:
> On Fri, Dec 6, 2019 at 7:19 PM Vincent Blut <vincent.debian@xxxxxxx> wrote:
>
> > On 2019-12-06T16:55+0100, Vincent Blut wrote:
> > >On 2019-12-06T10:21+0100, Christian Ehrhardt wrote:
> > >>Hi chrony-dev,
> > >>chrony is tested in Debian/Ubuntu on any update of related packages
> > >>and while that was running I found that arm64 and ppc64 reproducibly
> > >>hang [1][2]. OTOH arm64 and s390x reproducibly work.
> > >
> > >By the way, I just gave it a shot on an arm64 VM and the rtc test
> > >passed flawlessly. Note that this VM is powered by Linux 4.19.x.
> > >I will soon run that test with a more recent kernel.
> >
> > I still can’t reproduce the issue on an updated Debian unstable arm64 VM:
>
> My manual testing was on ppc64el, I only knew arm64 was affected from the
> runs at autopkgtest.ubuntu.com.
> Since you tried arm64 first I spun up a VM myself.

I think I will have access to a ppc64el system this week. We’ll see if I 
can reproduce this.

> The ppc64 system had 5.2.0-8-generic, this one now has 5.3.0-24-generic.
> I ran it again against the chrony master tarball with just the minimal
> setting I mentioned before:
>
> $ cat ~/chronyd.conf
> rtcfile /root/rtcfile
> $ cat /root/rtcfile
> 1 1575623140 0.0 0.0
> # ./chronyd -f /root/chronyd.conf -s -d
> 2019-12-09T10:58:13Z chronyd version DEVELOPMENT starting (+CMDMON +NTP
> +REFCLOCK +RTC +PRIVDROP -SCFILTER -SIGND +ASYNCDNS +SECHASH +IPV6 -DEBUG)
> 2019-12-09T10:58:14Z System time set from RTC
> 2019-12-09T10:58:14Z Initial frequency -10.245 ppm
> 2019-12-09T10:58:14Z Could not enable RTC interrupt : Invalid argument
> <hang>

I wonder if the RTC driver in use on your system is able to handle 
RTC_UIE_{ON,OFF} ioctl requests.

> All other symptoms (e.g. the defunct proc if running without -d and so on)
> are the same on this arm64 system.
>
> Just to check a bit of the rtc-config on those VMs between our cases:
> # ll /dev/rtc*
> lrwxrwxrwx 1 root root      4 Dec  9 10:42 /dev/rtc -> rtc0
> crw------- 1 root root 248, 0 Dec  9 10:42 /dev/rtc0
> # dmesg | grep rtc
> [    0.905564] rtc-efi rtc-efi: registered as rtc0
> [    1.082957] rtc-efi rtc-efi: setting system clock to 2019-12-09T10:41:00
> UTC (1575888060)

Ok, so I checked this driver’s code [1], and it doesn’t seem to be able 
to handle the aforementioned ioctl requests:

rtc->uie_unsupported = 1;

It would interesting to know if you can reproduce this issue by enabling 
the CONFIG_RTC_INTF_DEV_UIE_EMUL kernel module.

FWIW, my arm64 VM uses the rtc-pl031 driver.

Cheers,
Vincent

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