> > > after measuring the duration of the function udelay (with
oscilloscope
> > > at parallel port), I figured out that udelay (5usec) with
activated
> > > realtime- preempt patch lasts a little bit longer. Without the
patch the
> > > time is exact.
> > > All kernel debug switches are turned off at compile time.
> > > Can anyone suggest why this happens?
> >
> > Well, the -rt patch, has changed the udelay function. BTW, you are
> > using the constant udelay, right? Maybe an example of the code you
> > used to test might be useful.
> >
> > Ingo or John?
>
> yes, i found this problem too, a week ago or so. It's due to the GTOD
> changes to i386's __delay() function. Does it still occur with -rt15
> [which has the -B11 GTOD patchset] ?
I've done the first measurements only with rt5 and rt13.
Now with rt15 it looks fine (nice 5usec!)
fine patch, thanks!
christoph
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