2006-03-07 16:34:52

by Serge Noiraud

Subject: RT patch and arch/i386/kernel/time.c question

hi,

I'm trying to port the LTTng patch over the rt20 and I got the following problem :
The LTTng patch try to modify the arch/i386/kernel/time.c file in which the
timer_interrupt function doesn't exist anymore.

In which file / function could I try to patch the equivalent function ?

--
Serge Noiraud

2006-03-07 17:23:39

by Steven Rostedt

Subject: Re: RT patch and arch/i386/kernel/time.c question

On Tue, 7 Mar 2006, Serge Noiraud wrote:

> hi,
>
> I'm trying to port the LTTng patch over the rt20 and I got the following problem :
> The LTTng patch try to modify the arch/i386/kernel/time.c file in which the
> timer_interrupt function doesn't exist anymore.
>
> In which file / function could I try to patch the equivalent function ?
>

The -rt patch uses the lastest stuff from Thomas Gleixner, John Stultz and
of course Ingo Molnar. The functions you are interested in, are in
kernel/time/ directory. Take a look at clockevents.c and perhaps
handle_tick(). I'm not sure what LTTng is doing there, but this will give
you a direction in which way to look.

-- Steve

2006-03-07 17:45:21

by Mathieu Desnoyers

Subject: Re: RT patch and arch/i386/kernel/time.c question

* Steven Rostedt ([email protected]) wrote:
>
> On Tue, 7 Mar 2006, Serge Noiraud wrote:
>
> > hi,
> >
> > I'm trying to port the LTTng patch over the rt20 and I got the following problem :
> > The LTTng patch try to modify the arch/i386/kernel/time.c file in which the
> > timer_interrupt function doesn't exist anymore.
> >
> > In which file / function could I try to patch the equivalent function ?
> >
>
> The -rt patch uses the lastest stuff from Thomas Gleixner, John Stultz and
> of course Ingo Molnar. The functions you are interested in, are in
> kernel/time/ directory. Take a look at clockevents.c and perhaps
> handle_tick(). I'm not sure what LTTng is doing there, but this will give
> you a direction in which way to look.
>
> -- Steve
>

LTTng is updating its logical clock there. Note that this clock is only used on
architectures missing a synchronised CPU timestamp counter (NUMA and old i586).

If you have a fairly standard architecture (i686 with TSC available), this
combination of jiffies counter and logical clock is not used.

Look for where the xtime_lock seqlock is taken in the -rt patch : that's where
the logical clock should be updated.

Mathieu

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