Re: [PATCH] Improve clocksource unstable warning

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

On Fri, 2010-11-12 at 18:48 -0500, Andrew Lutomirski wrote:
> On Fri, Nov 12, 2010 at 6:40 PM, john stultz <johnstul@us.ibm.com> wrote:
> > On Fri, 2010-11-12 at 16:52 -0500, Andrew Lutomirski wrote:
> >
> >> if ( wd_elapsed < cs_elapsed and ( (cs_elapsed - wd_elapsed) %
> >> wd_wrapping_time ) < (something fairly small) )
> >>   bail;  // The watchdog most likely wrapped.
> >
> > Huh. The modulo bit may need tweaking as its not immediately clear its
> > right. Maybe the following is clearer?:
> >
> > if ((cs_elapsed > wd_wrapping_time)
> >        && (abs((cs_elapsed % wd_wrapping_time)-wd_elapsed) < MAX_DELTA)
> >        // should be ok.
> 
> I think this is wrong if wd_elapsed is large (which could happen if
> the real wd time is something like (2 * wd_wrapping_time -
> MAX_DELTA/4)).

But wd_elapsed can never be larger then wd_wrapping_time, right?

Or am I still missing something?

thanks
-john