Re: [uml-devel] actually useful backtrace from a CPU-chewing hang

[Nix <nix@esperi.org.uk>]

On 26 Apr 2008, nix@esperi.org.uk uttered the following:

> On 25 Apr 2008, nix@esperi.org.uk uttered the following:
>
>> On 25 Apr 2008, nix@esperi.org.uk told this:
>>
>>> I suspect this can go wrong anywhere, but it happens to have been a
>>> CBQ-triggered gettimeofday() while sending an arp that did it. (My ADSL
>>> router pretty much bombs the poor damn machine with ARP packets all the
>>> time.)
>>
>> Woo, it's happening a lot tonight.
>
> The cause of this is almost certainly time-skewing on the *host* via
> adjtimex(). I stopped ntpd and there were no problems for half a day: I
> restarted it, and as soon as ntpd had synched and begun slewing the time
> (within a second of slewing beginning, probably less than that), *wham*:

Time-stepping on the host is enough to cause trouble. I switched to
using ntpdate -b to keep time in synch, and since then my UML instances
have gone into mad loops only on the hour, when the ntpdate time-step
should take place.

-- 
`If you are having a "ua luea luea le ua le" kind of day, I can only
 assume that you are doing no work due [to] incapacitating nausea caused 
 by numerous lazy demons.' --- Frossie

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