Re: [patch 11/13] s390: instruction processing damage handling.

[Paulo Marques]

Martin Schwidefsky wrote:
> On Fri, 2006-04-28 at 10:39 +0200, Heiko Carstens wrote:
>
> > > > +++ linux-2.6-patched/drivers/s390/s390mach.c	2006-04-24 16:47:28.000000000 +0200
> > > ...
> > > > +#define MAX_IPD_TIME	(5 * 60 * 100 * 1000) /* 5 minutes */
                                ^^^^^^^^^^^^^^^^^^^^
				Expression A

> > > I'm no s390 expert, but shouldn't the above use something like HZ?
> >
> > Using HZ here feels just wrong to me. MAX_IPD_TIME has nothing to do with the
> > timer frequency. In this case it's used to tell if there were 30 machine
> > checks within the last 5 minutes (in a usec granularity). It's just by
> > accident that this could be expressed using HZ.
> > (5 * 60 * USEC_PER_SEC) would probably look better...
  ^^^^^^^^^^^^^^^^^^^^^^^
  Expression B

I'm no s390 expert either, but just wanted to point out that expression 
B is 10 times larger than expression A, so something's fishy here.

> Using HZ would be wrong. The check that uses MAX_IPD_TIME compares it
> against the result of a get_clock() call. That uses the TOD Clock
> directly, there is no dependency on HZ.

Looking at include/asm-s390/timex.h:

#define CLOCK_TICK_RATE	1193180 /* Underlying HZ */

makes me wonder if this should be:

#define MAX_IPD_TIME	(5 * 60 * CLOCK_TICK_RATE) /* 5 minutes */

--
Paulo Marques - www.grupopie.com

Pointy-Haired Boss: I don't see anything that could stand in our way.
           Dilbert: Sanity? Reality? The laws of physics?
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