kern/156168: Kernel panic under concurrent access over NFS

[Nikita]

>Number:         156168
>Category:       kern
>Synopsis:       Kernel panic under concurrent access over NFS
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Mon Apr 04 07:10:10 UTC 2011
>Closed-Date:
>Last-Modified:
>Originator:     Nikita
>Release:        FreeBSD 8.2-RELEASE #0
>Organization:
>Environment:
FreeBSD achilles.hstg.ru 8.2-RELEASE FreeBSD 8.2-RELEASE #0: Fri Feb 18 02:24:46 UTC 2011     root at almeida.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  i386
>Description:
I have 3 apache22-itk web servers with DOCUMENT_ROOT shared over NFS.
Sometimes i get kernel panic:

Fatal trap 12: page fault while in kernel mode
cpuid = 3; apic id = 03
fault virtual address   = 0x10
fault code              = supervisor write, page not present
instruction pointer     = 0x20:0xc0aa3236
stack pointer           = 0x28:0xea1ae528
frame pointer           = 0x28:0xea1ae5f4
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, def32 1, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 78988 (httpd)
trap number             = 12
panic: page fault
cpuid = 3
KDB: stack backtrace:
#0 0xc08e0d07 at kdb_backtrace+0x47
#1 0xc08b1dc7 at panic+0x117
#2 0xc0be4b43 at trap_fatal+0x323
#3 0xc0be4dc0 at trap_pfault+0x270
#4 0xc0be5305 at trap+0x465
#5 0xc0bcbebc at calltrap+0x6
#6 0xc0aa89c7 at clnt_call_private+0xf7
#7 0xc0a97dcb at nlm_get_rpc+0x19b
#8 0xc0a98379 at nlm_host_get_rpc+0x169
#9 0xc0a949eb at nlm_clearlock+0xeb
#10 0xc0a95d2a at nlm_advlock_internal+0x9ca
#11 0xc0a9651a at nlm_advlock+0x3a
#12 0xc0a80239 at nfs_advlock+0xa9
#13 0xc0c038c7 at VOP_ADVLOCK_APV+0x47
#14 0xc0875dee at closef+0xfe
#15 0xc087653f at kern_close+0x17f
#16 0xc087661a at close+0x1a
#17 0xc08eca39 at syscallenter+0x329
Uptime: 6d22h54m7s
Physical memory: 3059 MB
Dumping 335 MB: 320 304 288 272 256 240 224 208 192 176 160 144 128 112 96 80 64 48 32 16
>How-To-Repeat:

>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: