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

[Paulo Marques <pmarques@grupopie.com>]

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

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