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From: "Rodney W. Grimes" <rgrimes@GndRsh.aac.dev.com>
Message-Id: <199601031755.JAA28812@GndRsh.aac.dev.com>
Subject: Re: Another 2.1 panic :-(
To: gpalmer@westhill.cdrom.com
Date: Wed, 3 Jan 1996 09:55:08 -0800 (PST)
Cc: freebsd-stable@freebsd.org
In-Reply-To: <8926.820660026@westhill.cdrom.com> from "gpalmer@westhill.cdrom.com" at Jan 3, 96 01:07:06 am
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> 
> 
> Hi guys.
> 
> Same machine, different panic:
> 
> IdlePTD 1f3000
> current pcb at 1ca3e0
> panic: ufs_unlock NOT LOCKED
> #0  boot (howto=260) at ../../i386/i386/machdep.c:892
...

> 
> This is on a CDROM that was just mounted, and the command that seemed
> to do it was a `ls' of the directory the CDROM was mounted on. I just
> noticed that the twit which did this did:
> 
> cd /cdrom
> ls
> mount /cdrom
> ls
> <panic>
> 
> Still, it should not have happened...
> 
> Again, core file available.

It didn't panic my system but I saw a very similiar thing the
other night, let me see if I can reproduce it:
SkyRsh# umount /mnt
SkyRsh# cd /mnt
SkyRsh# ls
SkyRsh# mount /dev/sd1a /mnt
SkyRsh# ls
disks           tfs             tmp
SkyRsh# ls disks   
ls: disks: No such file or directory
SkyRsh# cd disks
disks: No such file or directory.
SkyRsh# ls
disks           tfs             tmp
SkyRsh# ls -lag
total 5
drwxr-xr-x   5 root     wheel    512 Jan  1 17:23 .
drwxr-xr-x  20 root     wheel    512 Dec 23 16:50 ..
drwxr-xr-x  13 root     wheel    512 Dec  2 12:44 disks
drwxr-xr-x   2 rgrimes  rgrimes  512 Jul 27 12:12 tfs
drwxrwxrwt   3 root     wheel    512 Jan  1 17:23 tmp
SkyRsh# cd /mnt
SkyRsh# ls
archie.jpeg     disks           tfs             tmp
SkyRsh# ls disks
#9              brother         kouwell         novell
adaptec         di              microsoft       osf1
asus            ecs             miro
SkyRsh# 

Seems that the mount code is allowing you to mount over a ``busy''
directory :-(.

-- 
Rod Grimes                                      rgrimes@gndrsh.aac.dev.com
Accurate Automation Company                 Reliable computers for FreeBSD