Messages in this thread | | | Subject | Re: System time warping around real time problem - please help | From | Fionn Behrens <> | Date | 25 Mar 2003 19:12:37 +0100 |
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On Die, 2003-03-25 at 18:07, Richard B. Johnson wrote: > On Tue, 25 Mar 2003, Fionn Behrens wrote:
> > I have got an increasingly annoying problem with our fairly new (fall > > '02) Dual Athlon2k+ Gigabyte 7dpxdw linux system running 2.4.20.
> I am using the exact same kernel (a lot of folks are). There > is no such jumping on my system. > Try this program:
[... prg1.c ...]
> If this shows time jumping around you have one of either: > > (1) Bad timer channel 0 chip (PIT). > (2) Some daemon trying to sync time with another system. > (3) You are traveling too close to the speed of light.
It just exits immediately with exit code 1. (*shrug*)
> Now, your script shows time in fractional seconds. > > > 1048608745.61 > 1048608745.60 > > You can modify the program to do this:
[... prg2.c ...]
> There should be no jumping around -- and there isn't on > any system I've tested this on.
When I run this code it begins to put out Prev N New M lines.
Prev 1048615862810879.000000 New 1048615862759879.000000 Prev 1048615862870879.000000 New 1048615862819878.000000 Prev 1048615862900879.000000 New 1048615862849902.000000 Prev 1048615862960882.000000 New 1048615862909875.000000 [-------- cut --------]
After a few seconds of run time random processes on my machine begin to crash, or I get kernel oopses and kernel freezes. Looks very much like heavy use of gettimeofday() causes random writes in system memory.
> > Software crashes are regularly - naturally. No programmer expects system > > timers going back in time.
> Hmmm, software should never crash. Even if the timers jump backwards > as you say, they should eventually time-out. If you have crashes, this > may point to other hardware problems as well.
E.g. which type of hardware problem?
Thanks a million for your help so far, it is great to experience how fast people are respoding!
I'll evaluate that other suggestion about TSC_DISABLE now and will get back to you as soon as I can tell you more.
Kind regards, F. Behrens - 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/
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