kern/38778: /kern files do not show up anymore after quite some time

[njoly%pasteur.fr@localhost]

>Number:         38778
>Category:       kern
>Synopsis:       /kern files do not show up anymore after quite some time
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed May 28 12:45:00 +0000 2008
>Originator:     Nicolas Joly
>Release:        NetBSD 4.99.63
>Organization:
Biological Software and Databanks.
Institut Pasteur, Paris.
>Environment:
System: NetBSD lanfeust.sis.pasteur.fr 4.99.63 NetBSD 4.99.63 (LANFEUST) #16: 
Wed May 28 13:08:09 CEST 2008 
njoly%lanfeust.sis.pasteur.fr@localhost:/local/src/NetBSD/obj.amd64/sys/arch/amd64/compile/LANFEUST
 amd64
Architecture: x86_64
Machine: amd64
>Description:
On a freshly booted system there is no problems to see files under /kern;
after quite some time/use (cvs up src + kerne build), they do not show
up anymore but remain available.

njoly@lanfeust [NetBSD/src]> mount -t kernfs -v 
kernfs on /kern type kernfs (local, fsid: 0x8b01/0x1d28b, reads: sync 0 async 
0, writes: sync 0 async 0)
njoly@lanfeust [NetBSD/src]> ls -l /kern
total 63
-r--r--r--  1 root  wheel             11 May 28 13:55 boottime
-r--r--r--  1 root  wheel            264 May 28 14:04 copyright
-rw-r--r--  1 root  wheel             24 May 28 14:04 hostname
-r--r--r--  1 root  wheel              4 May 28 14:04 hz
-r--r--r--  1 root  wheel             11 May 28 14:04 loadavg
-r--r--r--  1 root  wheel          32736 May 28 14:04 msgbuf
-r--r--r--  1 root  wheel              5 May 28 14:04 pagesize
-r--r--r--  1 root  wheel              7 May 28 14:04 physmem
brw-r-----  1 root  operator        0, 0 Mar 21  2005 rootdev
crw-r-----  1 root  operator        3, 0 Nov  4  2005 rrootdev
-r--r--r--  1 root  wheel             18 May 28 14:04 time
-r--r--r--  1 root  wheel            152 May 28 14:04 version
njoly@lanfeust [NetBSD/src]> cvs -q up                              
[...]
njoly@lanfeust [NetBSD/src]> ./build.sh -Uu -m amd64 kernel=LANFEUST
[...]
njoly@lanfeust [NetBSD/src]> ls -l /kern
njoly@lanfeust [NetBSD/src]> ls -l /kern/loadavg
-r--r--r--  1 root  wheel  13 May 28 14:39 /kern/loadavg
njoly@lanfeust [NetBSD/src]> cat /kern/loadavg
0 0 109 2048

Here is the corresponding trace:
 14255      1 ls       CALL  open(0x7f7ffd803400,4,0)
 14255      1 ls       NAMI  "/kern"
 14255      1 ls       RET   open 4
[...]
 14255      1 ls       CALL  lseek(4,0,0,1)
 14255      1 ls       RET   lseek 0
 14255      1 ls       CALL  __getdents30(4,0x7f7ffd813000,0x1000)
 14255      1 ls       RET   __getdents30 -1 errno 9 Bad file descriptor
 14255      1 ls       CALL  close(4)
 14255      1 ls       RET   close 0

This is mostly from a GENERIC+DIAGNOSTIC kernel, with a few other devices.
>How-To-Repeat:
ls -l /kern
[do some other stuff ...]
ls -l /kern
>Fix:
n/a