system stalls when wallclock/TOD nudged

[Colin Percival]

On 11/19/10 23:40, Adrian Chadd wrote:
> I bet if you did some slicing of -head versions, you'll find an
> earlier version that doesn't do that. :-)

Sure, all I need to do is go back a couple of days, and I find a FreeBSD
Xen kernel which doesn't do this... because it panics before the clock
gets nudged. :-)

> On 20 November 2010 15:38, Colin Percival <cperciva at freebsd.org> wrote:
>> It seems that this bug is related somehow to the idle thread sleeping -- when
>> I comment out the call to idle_block from cpu_idle_hlt in i386/machdep.c the
>> stalling goes away.
>>
>>> On Fri, 2010-11-19 at 06:42 -0800, Colin Percival wrote:
>>>> During the boot process, in the middle of running rc.d scripts, my FreeBSD/Xen
>>>> instance stalls.  It does nothing until I send a shutdown signal, at which point
>>>>> [XEN] hypervisor wallclock nudged; nudging TOD.
>>>> and a couple buffered lines of rc.d script output are printed.  From there the
>>>> rc.shutdown script starts running, but it too stalls after a short time; then I
>>>> see
>>>>> [XEN] hypervisor wallclock nudged; nudging TOD.
>>>>> Nov 19 14:08:33 init: timeout expired for /bin/sh on /etc/rc.shutdown: Interrupted system call; going to single user mode
>>>> printed, suggesting that the shutdown watchdog timer at least managed to not get
>>>> stuck even though everything else did.

-- 
Colin Percival
Security Officer, FreeBSD | freebsd.org | The power to serve
Founder / author, Tarsnap | tarsnap.com | Online backups for the truly paranoid