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Date:      Sun, 18 Jan 1998 10:28:40 -0600 (CST)
From:      Neal <neal@pernet.net>
To:        Doug White <dwhite@resnet.uoregon.edu>
Cc:        freebsd-questions@FreeBSD.ORG
Subject:   Re: double kernel faults
Message-ID:  <Pine.BSF.3.95q.980118102414.25854C-100000@office.pernet.net>
In-Reply-To: <Pine.BSF.3.96.980117211850.6065P-100000@gdi.uoregon.edu>

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Nope.  The second fault appears to happen when the kernel tries to sync
the disks.  I haven't traced ALL the way back, but it looks like this,
time order being top is the start of the fault:

actual fault happens
trap() is called
sync() is called
msync() is called
second fault happens
trap() called
sync() called
msync() called
reboots correctly.

I don't have my notes handy(I'm in Houston for the weekend, yeah!), but
I've found the actual location of the panic.  Someplace along the
line(inside of sync()), the vfs struct is dissapearing.  When the actual
sysctl macro gets called, on of the arguments is a pointer to a pointer
from a NULL.

I'll send a stack trace when I get back local.

On Sat, 17 Jan 1998, Doug White wrote:

> On Fri, 16 Jan 1998, Neal Rigney wrote:
> 
> > 
> > I've got a news machine that continually page faults(I'm tracking the
> > problem down right now), but here's the interesting question:
> > 
> > When it page faults, it ALWAYS(with this error) faults a second time.  In
> > other words, I get "page fault while in kernel mode" etc(the REAL error I
> > want to look at) immediately followed by another fault that of course
> > scrolls all the information from the first fault off the screen.
> > 
> > So, should I _really_ worry about the second fault, or chaulk it up to the
> > first fault making the system go nuts?
> 
> I'd be more interested in what the second fault is so we can resolve that
> so we can actually *see* the details on the first fault ;-)
> 
> Does the `scroll lock-up arrow' scrollback work during a panic?  I forgot.
> 
> Doug White                              | University of Oregon  
> Internet:  dwhite@resnet.uoregon.edu    | Residence Networking Assistant
> http://gladstone.uoregon.edu/~dwhite    | Computer Science Major
> 
> 
> 

--
Neal Rigney, PERnet Communications, (409)729-4638
neal@mail.pernet.net





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