100% reproducible panic with pseudofs

[Roman Divacky]

hi

with -current as of 2nd April I can reliable panic the system in pseudofs with
the following command sequence:

mount /proc
cat /proc/123/status
umount /proc
kldunload procfs
<PANIC>

the same panic is here with linprocfs so I think its pseudofs related. I cannot
get the backtrace so I had to rewrite it by hand:

kern_kldunload();
linker_file_unload();
module_unload();
vfs_modevent();
_procfs_uninit();
pfs_uninit();
delete_unrhdr()
PANIC;

it panics on KASSERT(uh->busy == 0, ("unrhdr has %u allocations", uh->busy)); so to reproduce this
panic you have to have INVARIANTS enabled kernel...

thnx

roman