Re: gettimeofday() jumping into the future

[Avi Kivity <avi@argo.co.il>]

Gerald Britton wrote:
> On Thu, Aug 23, 2007 at 01:08:27PM +0200, Michael Smith wrote:
>   
> > Hi,
> >
> > We've been seeing some strange behaviour on some of our applications
> > recently. I've tracked this down to gettimeofday() returning spurious
> > values occasionally.
> >
> > Specifically, gettimeofday() will suddenly, for a single call, return
> > a value about 4398 seconds (~1 hour 13 minutes) in the future. The
> > following call goes back to a normal value.
> >     
>
> I have seen this as well (on a 2.6.20.4 kernel).  The value returned was
> always identical each time the glitch occured (just a little over 4398
> seconds).  I saw it watching packet receive timestamps and on the system in
> question, it would generally hit this problem around once a minute.  When
> moving forward to a 2.6.21 kernel, the problem seemed to go away (also back
> to 2.6.17, unfortunately I didn't have any sample points inbetween).
> I didn't have free time to spend bisecting attempting to find when the
> behavior started or stopped.
>
>   

That value, in nanoseconds, is 0x3fffd3a4c00.  The next second is 
0x40038d51600.  Is the wraparound at (0x400 << 32) significant?

--
error compiling committee.c: too many arguments to function

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/