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At Fri, 20 Apr 2007 12:46:53 +0100 (BST), Stephen Borrill wrote:
Subject: Re: 3.1_STABLE and SMP
>=20
> Interesting. Usually the servers in questions run a proxy, NAT and
> sendmail and so any hang kills Internet access for the customers, so they
> tend to want to reboot rather than help us investigate.

I can understand that!  :-)

> > Do you have a DDB stack backtrace, assuming you can get into DDB from
> > the hung state?
>=20
> I got emailed a screenshot of one:
> http://projects.precedence.co.uk/netbsd/ddb1.jpg

Hopefully that'll mean something to someone.  :-)

> > Could you build at your kernel with LOCKDEBUG defined too?  (I prefer
> > building all of userland with LOCKDEBUG defined too, just for those few
> > kmem grovelers that need to know how LOCKDEBUG affects kernel
> > structures, but if the problem is easy to reproduce then you should only
> > need to run with the LOCKDEBUG kernel for a short while)
>=20
> I've not done that yet, but I will do. What extra debug info does this
> give? i.e. what do I tell the customer to do next time it crashes when
> they are running a LOCKDEBUG kernel?

On the alpha I get a little more console output, if it's something like
a simple_lock() "locking against myself" contention, for example.  In
those cases you can then call a debug function from DDB to get even more
info, e.g. like this:

	db{0}> call simple_lock_dump()

Perhaps someone else can provide some more suggestions too.

--=20
						Greg A. Woods

H:+1 416 218-0098 W:+1 416 489-5852 x122 VE3TCP RoboHack <woods@robohack.ca>
Planix, Inc. <woods@planix.com>       Secrets of the Weird <woods@weird.com>

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