DragonFlyBSD

Weird ls behavior on cache_resolve().
stat(".",0x7fffffffee70) ERR#57 'Socket is not connected'
lstat(".",0x7fffffffee70) ERR#57 'Socket is not connected'
open(".",0x20000,00) ERR#57 'Socket is not connected'

This is namei lookup issue.
This has existed since at least 4.0 or 4.2.

hammer
[root@]~# mount_hammer /dev/da1:/dev/da2:/dev/da3 /mnt
[root@]~# cd /mnt
[root@]/mnt# umount /mnt
umount: unmount of /mnt failed: Device busy
[root@]/mnt# ls
ls: .: Socket is not connected
[root@]/mnt# ls
ls: .: Socket is not connected
[root@]/mnt# ls
ls: .: Socket is not connected
[root@]/mnt# cd
[root@]~# ls /mnt
[root@]~# umount /mnt

tmpfs
[root@]~# mount_tmpfs none /mnt
[root@]~# cd /mnt
[root@]/mnt# umount /mnt
umount: unmount of /mnt failed: Device busy
[root@]/mnt# ls
ls: .: Socket is not connected
[root@]/mnt# ls
ls: .: Socket is not connected
[root@]/mnt# ls
ls: .: Socket is not connected
[root@]/mnt# cd
[root@]~# ls /mnt
[root@]~# umount /mnt

warnings in dmesg
[root@]~# dmesg | tail -6
Warning: cache_resolve: ncp '(null)' was unlinked
Warning: cache_resolve: ncp '(null)' was unlinked
Warning: cache_resolve: ncp '(null)' was unlinked
Warning: cache_resolve: ncp '(null)' was unlinked
Warning: cache_resolve: ncp '(null)' was unlinked
Warning: cache_resolve: ncp '(null)' was unlinked

On FreeBSD
[root@]~# uname -r
11.0-CURRENT
[root@]~# mount -t tmpfs none /mnt
[root@]~# cd /mnt
[root@]/mnt# umount /mnt
umount: unmount of /mnt failed: Device busy
[root@]/mnt# ls
[root@]/mnt# ls
[root@]/mnt# ls
[root@]/mnt# cd
[root@]~# ls /mnt
[root@]~# umount /mnt