double fault when nullmounting

["Simon 'corecode' Schubert" <corecode@xxxxxxxxxxxx>]

hey,

I just got this double fault when I was doing some layered mounts:

Fatal double fault
eip=0xc034a27a
esp=0ce2426ffc
ebp=0xe2427000

. ..
trapwrite(0,c64e0760,0,0,0)

I'll look the symbols up.  I guess that was a stack overflow, the second one.

This is a two processor hyperthreading Xeon (4 logical CPUs), SMP kernel.

The mounting was something like this:

server:/pbulk on /pbulk	nfs
/dev/ad6s1b on /pbulk2	ufs
/pbulk2/root on /pbulk/root	null
/pbulk2/clients on /pbulk/clients	null
/pbulk/root on /pbulk/clients/subdir/root	null,ro
/pbulk/clients/subdir/var on /pbulk/clients/subdir/root/var	null
/pbulk/clients/subdir/tmp on /pbulk/clients/subdir/root/tmp	null
/pbulk/clients/subdir/dev on /pbulk/clients/subdir/root/dev	null
/pbulk/clients/subdir/usr.pkg on /pbulk/clients/subdir/root/usr/pkg	null

there it paniced.  however, I was doing that from a shell script, so maybe something unfinished before was doing it.  This was kind of reproducable:  I did the same sequence one time before and the box just rebooted.

I probably won't be able to reproduce this because the machine is part of a cluster of our lab and it is in a server room, meaning other people want to use it, it is cold there, I have other stuff to do :/

cheers
 simon

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