Re: [BUG,2.6.28,s390] Fails to boot in Hercules S/390 emulator

john stultz
2009-03-17T05:15:28Z

On Thu, 2009-03-12 at 07:51 +0100, Frans Pop wrote:
> On Thursday 12 March 2009, John Stultz wrote:
> > * Reverting both 6c9bacb41c10 and 5cd1c9c5cf30 against 2.6-git did not
> > seem to help the issue, as originally reported. I also reverted
> > 49b5cf34727a as well just in case, and it didn't help either.
>
> Hmm, interesting. I think you may have reproduced a similar failure case,
> but not exactly the same as mine. I wonder if what you have reproduced is
> the same as Debian bug report http://bugs.debian.org/511334. That is with
> 2.6.26 which would match the fact that the reverts that work reliably for
> me did not work for you. I've never had any problems with Debian's 2.6.26
> in my configuration.

Hmmm. I have indeed seen issues w/ the 2.6.26 debian kernel, so that
does seem closer to what I'm seeing.

> For me 2.6.28.7 is rock solid with the two reverts. I've attached my
> kernel config and my Hercules config. I think the critical thing in my
> config may be the "TIMERINT 500" setting for Hercules, which is somewhat
> similar to your "goes away if HZ is anything except 250" observation.

I'll have to checkout that option. Does changing HZ value or disabling
NO_HZ change anything for your situation as well?

> > That's about all I can get for today. I'm out of town until Monday, so
> > I'll start digging back into it then.
>
> From your other replies I've seen that I have been way off track at some
> points. It looks as if I have been looking at events too early in the
> boot and been confused by the use of clock->xtime_nsec. My apologies for
> any confusion caused by that.
>
> I have a few more tests I think I can usefully do, but will try harder not
> to confuse the issue with my inexpert ramblings anymore :-P

No, no, this is subtle and optimized code that keeps very high precision
values. Its not trivial stuff, so your confusion is understandable.

thanks
-john