Re: [PATCH] Re: boot time, process start time, and NOW time

[George Anzinger <george@mvista.com>]

OGAWA Hirofumi wrote:
> Tim Schmielau <tim@physik3.uni-rostock.de> writes:
> 
> 
>>However, the actual reason were just missing wall_to_monotonic 
>>initializations:
>>
>>  http://www.uwsg.iu.edu/hypermail/linux/kernel/0306.2/1330.html
> 
> 
> Sorry for may not be related question in this thread.
> 
> 
>          xtime.tv_nsec = (INITIAL_JIFFIES % HZ) * (NSEC_PER_SEC / HZ);
> 
> #include <stdio.h>
> 
> #define HZ 1000
> #define NSEC_PER_SEC (1000000000L)
> #define INITIAL_JIFFIES ((unsigned long)(unsigned int) (-300*HZ))
> 
> int main()
> {
> 	printf("%ld\n", (INITIAL_JIFFIES % HZ) * (NSEC_PER_SEC / HZ));
> 	return 0;
> }
> 
> hirofumi@devron (a)[1006]$ ./c
> 296000000
> 
> xtime.tv_nsec was not 0. Is this bug?

Well, my machine says the result should be 996000000, so something is wrong with 
your or my math.  As to if the initial jiffie value should be a multiple of HZ, 
I don't see why.  I think it is several counts off of this value when the system 
wall clock is set in any case.

-- 
George Anzinger   george@mvista.com
High-res-timers:  http://sourceforge.net/projects/high-res-timers/
Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml