xen-wdt questions

xen-wdt questions

[Laszlo Ersek]

Hi,

I tried to test xen-wdt (as of 066d6c7) with
Documentation/watchdog/src/watchdog-test.c:

(1) when the test tool is invoked as "./watchdog-test -d", it exercises
WDIOC_SETOPTIONS/WDIOS_DISABLECARD, prints "Watchdog card disabled.",
and then closes /dev/watchdog.

That ioctl stops the watchdog alright via the hypercall and zeroes out
the guets's "wdt", but in repsonse to the closure (since
"expect_release" is not set) the xen_wdt_release() function prints a
critical message to the console ("unexpected close, not stopping
watchdog!"), and tries to kick it again. (At this time the guest's
wdt.id is 0, and so xen_wdt_kick() returns -ENXIO, but xen_wdt_release()
ignorese it.) The watchdog is stopped for real and the domain is not
killed, but the KERN_CRIT message could be misleading.

(2) Additionally, the WDIOC_SETOPTIONS/WDIOS_DISABLECARD ioctl manages
to turn off the watchdog, even if nowayout=1 was passed to the xen-wdt
module. Is that intentional?

Thanks
Laszlo

Re: xen-wdt questions

[Jan Beulich]

>>> On 05.10.11 at 15:08, Laszlo Ersek <lersek@redhat.com> wrote:
> Hi,
> 
> I tried to test xen-wdt (as of 066d6c7) with
> Documentation/watchdog/src/watchdog-test.c:
> 
> (1) when the test tool is invoked as "./watchdog-test -d", it exercises
> WDIOC_SETOPTIONS/WDIOS_DISABLECARD, prints "Watchdog card disabled.",
> and then closes /dev/watchdog.
> 
> That ioctl stops the watchdog alright via the hypercall and zeroes out
> the guets's "wdt", but in repsonse to the closure (since
> "expect_release" is not set) the xen_wdt_release() function prints a
> critical message to the console ("unexpected close, not stopping
> watchdog!"), and tries to kick it again. (At this time the guest's
> wdt.id is 0, and so xen_wdt_kick() returns -ENXIO, but xen_wdt_release()
> ignorese it.) The watchdog is stopped for real and the domain is not
> killed, but the KERN_CRIT message could be misleading.
> 
> (2) Additionally, the WDIOC_SETOPTIONS/WDIOS_DISABLECARD ioctl manages
> to turn off the watchdog, even if nowayout=1 was passed to the xen-wdt
> module. Is that intentional?

I cloned some other watchdog driver's code when putting together the
Xen one, and I didn't test anything beyond basic watchdog functionality
(being able to reboot a guest and being able to cancel the watchdog).

Any ioctl anomalies are likely unintentional, but subject to knowing
respective behavior of the other watchdog drivers.

Jan

> 
> Thanks
> Laszlo