Date: Wed, 13 Jun 2001 01:24:28 -0700 From: Mike Smith <msmith@freebsd.org> To: Pete French <pfrench@firstcallgroup.co.uk> Cc: stable@FreeBSD.ORG Subject: Re: Very odd clock problem Message-ID: <200106130824.f5D8OSn08506@mass.dis.org> In-Reply-To: Your message of "Mon, 11 Jun 2001 10:47:54 BST." <E159OIc-000Pd8-00@dilbert.fcg.co.uk>
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> > Er, the system clock is not capable of representing the year 1933 (in any
> > valid fashion).
>
> Well it surpised me too ! Can the system clock not take negative values
> like time_t then ? (whatever type time_t happens to be this week :-) )
> I was assuming it was a signed 32 bit number and was getting set to
> something like 0xBB000000 or thereabouts.
Yes, it can *take* a negative value, but because it's typically
manipulated through arithemetic with other time_t's, it'd be fairly hard
for it to suddenly become large and negative by any legitimate means.
> > This sounds like either memory corruption or an in-kernel sniper bug of
> > some sort. You don't help the diagnosis any by saying "losing time" and
> > then complaining about a "jump". The two are very different things, and
> > you need to be much more specific about what is actually happening.
>
> Fair comment.
>
> What happens specificly is this: I get a user (and its always the same user)
> who complains that the dates on his outgoing emails are being timestamped in
> 1933. I login, type 'date' and sure enough it says it is a date in
> 1933. I then reset the date. There is nothing in the log files to indicate
> what has happened - other than the date on other messages jumping back
> to sometime in May (the year isnt logged in /var/log/messages I assume,
> but the month change is very obvious and I am assuming this co-incides
> with the year date change).
Why is it only this user? Are they your only user that cares? Or does
the time step only happen when they are sending mail?
> We were running ntpd, and stopped in case it was a corrupt ntp server
> somewhere. That didnt help. We have also changed ntp servers to a different
> set of machines. Once again to no effect. Could this be a clock
> battery problem at all ? I wouldnt have thought the battery was used
> with the machine powered up, but it is the only thing
> I can think of off the top of my head. It happened again this morning,
> there is no pattern to when the jumps occur that I can see.
It's unlikely to be the clock battery; the clock is only read at startup;
the system maintains time itself after that (keeping the clock in sync).
I'm really at a loss here; as I said, it sounds like a very specific
kernel sniper bug of some sort. 8(
--
... every activity meets with opposition, everyone who acts has his
rivals and unfortunately opponents also. But not because people want
to be opponents, rather because the tasks and relationships force
people to take different points of view. [Dr. Fritz Todt]
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