kern/45119: Assert Panic under -current running single proc under nfs load

[cyber%netbsd.org@localhost]

>Number:         45119
>Category:       kern
>Synopsis:       Assert Panic under -current running single proc under nfs load
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Jul 04 23:35:00 +0000 2011
>Originator:     Erik Berls
>Release:        -current July 4, 2011 14:30 PDT
>Organization:
NetBSD
>Environment:
NetBSD dev0 5.99.54 NetBSD 5.99.54 (GENERIC) #0: Mon Jul  4 07:57:10 PDT 2011  
cyber@dev0:/n/srv0/Src/N-current/src/sys/arch/amd64/compile/obj/GENERIC amd64

(Ignore build timestamp, clock is set wrong.)
>Description:
Running single user mode (see port-amd64/45118) on a Dell C521 under NFS load 
caused a assert panic.  USB keyboard was non-functional in ddb, so further 
backtrace was not possible.  top and iostat were running.

NIC was a bge.  nfs client was a system running NetBSD 5.1.


panic: kernel diagnostic assertion "ccp - *(ap->a_cookies) < ccount" failed: 
file "/n/srv0/Src/N-current/src/sys/ufs/ufs/ufs_vnops.c", line 1749
fatal breakpoint trap in supervisor mode
trap type 1 code 0 rip ffffffff802404bd cs 8 rflags 246 cr2 ffff80000483d4000 
cpl 0 rsp ffff800048def560
Stopped in pid 210.5 (nfsd) at netbsd:breakpoint+0x5: leave
db{0}>

>How-To-Repeat:
- boot system with -1 to disable SMP
- run as nfs server exporting a local volume
- on client ran ./build.sh cleandir
- watch server panic
>Fix: