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

john stultz (johnstul@us.ibm.com)
11 Mar 2003 14:59:13 -0800


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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=20
> thing. In time.c, the gettimeofday code calls get_offset() and then=20
> adds in lost ticks (ticks clocked by the PIT interrupt but not yet=20
> rolled into the wall clock (xtime). I was thinking that get_offset=20
> 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=20
> is in the common kernel and needs the result returned by get_offset=20
> OR, we could define a new function, get_monotonictimeofday(), which=20
> returns the jiffies since boot + get_offset() + pending ticks (i.e. it=20
> would be the same as gettimeofday except it would use jiffies_64=20
> instead of xtime to get its result. The format would be a timespec,=20
> 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.=20

> This translates directly into a system call and is also used in the=20
> timers code to convert from wall clock time to jiffies time for timers.
>=20
> Either way, we have a bit of a mess due to the arch dependency. I=20
> don't really care which way it goes, but I do think it should be=20
> 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).=20

thanks
-john

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