Reproducible panic of 6.2 on double mount ntfs

[Jan Henrik Sylvester]

Hello!

With '/dev/ad0s1 /mnt/ad0s1 ntfs ro,noauto 0 0' in fstab, if I issue 
'mount /mnt/ad0s1' twice, I always get a panic with the message:

panic: lockmgr: locking against myself

If I issue 'mount_ntfs /dev/ad0s1 /mnt/ad0s1' twice, there is no panic. 
I only get 'mount_ntfs: /dev/ad0s1: Operation not permitted' as 
expected. For a different (non-ntfs) filesystem, using plain mount twice 
gives 'Operation not permitted', too.

System is:

FreeBSD janh.freebsd 6.2-RELEASE-p4 FreeBSD 6.2-RELEASE-p4 #0: Thu Apr 
26 17:55:55 UTC 2007 
root at i386-builder.daemonology.net:/usr/obj/usr/src/sys/SMP  i386

Can anyone reproduce this?

Just for my curiosity: What is mount doing differently than mount_ntfs?

Thanks,
Jan Henrik