time problem

time problem

Post by Ibrahim Hadda » Thu, 24 Jun 1999 04:00:00



Hello all,
I have red hat 6.0 and the time of the machine keeps to
change!! Although on the Win NT partition time is
always correct.
Any ideas on how to fix that?

Thanks.

- Ibra

 
 
 

1. System time warping around real time problem - please help

I am using the exact same kernel (a lot of folks are). There
is no such jumping on my system.
Try this program:

#include <stdio.h>
#include <time.h>
int main() {
   time_t x,y;
   (void)time(&x);
   (void)time(&y);
   for(;;) {
       (void)time(&x);
       if(x < y)
           printf("Prev %ld New %ld\n", y, x);
       y = x;
   }
   return 0;
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.

Now, your script shows time in fractional seconds.

You can modify the program to do this:

#include <stdio.h>
#include <sys/time.h>
int main() {
   struct timeval tv;
   double x, y;
   (void)gettimeofday(&tv, NULL);
   x = (double) tv.tv_sec * 1e6;
   x += (double) tv.tv_usec;
   y = x;
   for(;;) {
       (void)gettimeofday(&tv, NULL);
       x = (double) tv.tv_sec * 1e6;
       x += (double) tv.tv_usec;
       if(x < y)
           printf("Prev %f New %f\n", y, x);
       y = x;
   }
   return 0;

There should be no jumping around -- and there isn't on
any system I've tested this on.

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.

Cheers,
Dick Johnson
Penguin : Linux version 2.4.20 on an i686 machine (797.90 BogoMips).
Why is the government concerned about the lunatic fringe? Think about it.

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