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Date:      Sat, 22 Aug 1998 00:23:34 -0500 (EST)
From:      "John S. Dyson" <dyson@iquest.net>
To:        tlambert@primenet.com (Terry Lambert)
Cc:        sos@FreeBSD.ORG, tlambert@primenet.com, croot@btp1da.phy.uni-bayreuth.de, regnauld@deepo.prosa.dk, current@FreeBSD.ORG, smp@FreeBSD.ORG
Subject:   Re: softupdates and smp crash
Message-ID:  <199808220523.AAA19739@dyson.iquest.net>
In-Reply-To: <199808200641.XAA18028@usr02.primenet.com> from Terry Lambert at "Aug 20, 98 06:41:53 am"

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Terry Lambert said:
> > > > So we can still say that softupdates are broken, at least for SMP.
> > > 
> > > It would be more useful (than saying this) for people to characterize
> > > the problem they are getting so that we can find a discriminitory
> > > value.  I suggest:
> > 
> > I suggest reading Luoqi Chen's exelent explanation as why it breaks
> > under SMP (hint: it has nothing todo with HW setups).. 
> 
> Perhaps clock speed?  8-).
> 
> His post arrived in my mailbox after I responded to your post...
> 
> I'm also not convinced that this is the only possible cause of
> the problem; the VM code is hardly "assert" protected everywhere,
> so diagnosing this thing is not trivial.  Look at the VM fixes
> I recently did, which killed the bugs Karl Denniger was seeing
> in 75% of the cases, leaving 25% of the cases "clustered" (in his
> words), indicating a seperate problem, in addition to the ones I
> fixed, in a periodically executing code path.  I had suspected
> that this would be the case when I made the fix, since it doesn't
> account for the buggy behaviour I'm personally seeing.  8-(.
> 
I have to chime in here -- some of the "fixes" are work-arounds, and
there are still underlying VM problems.  It might be "good enough"
for 3.0, but I would suggest preparing for some rework to find the
root cause for the problem.

-- 
John                  | Never try to teach a pig to sing,
dyson@iquest.net      | it makes one look stupid
jdyson@nc.com         | and it irritates the pig.

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