Re: [RFC][PATCH] linux-2.5.64_monotonic-clock_A1

[john stultz <johnstul@us.ibm.com>]

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On Tue, 2003-03-11 at 14:39, george anzinger wrote:

> I must have confused you.  I am woking on a get time of day sort of 
> thing.  In time.c, the gettimeofday code calls get_offset() and then 
> adds in lost ticks (ticks clocked by the PIT interrupt but not yet 
> rolled into the wall clock (xtime).  I was thinking that get_offset 
> might be defined to add this its result.

I'm still not quite following that. But as long as we're both pointing
at the same code and grunting in agreement I think I'll just let it
slide ;)


> But, back to the problem I am trying to solve.  The posixtimers code 
> is in the common kernel and needs the result returned by get_offset 
> OR, we could define a new function, get_monotonictimeofday(), which 
> returns the jiffies since boot + get_offset() + pending ticks (i.e. it 
> would be the same as gettimeofday except it would use jiffies_64 
> instead of xtime to get its result.  The format would be a timespec, 
> i.e. the same as xtime.


Actually, what is the difference between the call you're trying to
implement and monotonic_clock() (outside of the timespec return)?  Could
you point me to the specific code you are describing? It sounds like
we're working on basically the same solution from two different angles. 


> This translates directly into a system call and is also used in the 
> timers code to convert from wall clock time to jiffies time for timers.
> 
> Either way, we have a bit of a mess due to the arch dependency.  I 
> don't really care which way it goes, but I do think it should be 
> resolved in 2.5.

Well, if the generic interfaces aren't providing what you need, then a
new interface needs to be considered. This is precisely what the
hangcheck-timer code ran into, and is why we're working on this
monotonic_clock() code (which is intended be arch independent in the
future). 

thanks
-john

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