Re: "Your system clock just jumped" on Debian+VMware ESX

[Roger Dingledine <arma@xxxxxxx>]

On Fri, Feb 29, 2008 at 09:01:48AM +0100, Florian Reitmeir wrote:
> > I continue to see Tor report errors of jumps in the system time from
> > 4397-4399 seconds. Strangely, this jump in time does not appear to be
> > reflected in the time stamp that Tor assigns to the error message.
> 
> maybe it will help getting some more light on the issue if you just install a
> cronjob which prints the output of "date" in a file, and then try to see
> if the issue is a tor bug or a kernel bug. 4300 secounds are a bit more than
> 60minutes.. so if its a kernel bug it should happen to other processes too.

The other hint here is that FreeBSD users used to see this problem,
until a recent fix to FreeBSD made it go away. But last I checked,
nobody has tracked down what the fix was.

What's happening inside Tor is that it goes to sleep until a new
event happens or until one second elapses. When it wakes up, it asks
gettimeofday() how much time passed, and in this case it finds that it
has travelled back in time 4397 seconds since the last time it asked.

I'm guessing this is a kernel thing, so running "date" a lot will probably
not help to notice it. Is gettimeofday() the wrong way to ask what time
it is under vmware? :)

--Roger