kern/51215: nfs client kernel crash

[6bone%6bone.informatik.uni-leipzig.de@localhost]

>Number:         51215
>Category:       kern
>Synopsis:       nfs client kernel crash
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Jun 04 09:50:00 +0000 2016
>Originator:     Uwe Toenjes
>Release:        nfs client kernel crash
>Organization:
University of Leipzig
>Environment:
NetBSD 7.0_STABLE
>Description:
in rare cases, under high nfs load the kernel crashes

0xffffffff8068630f in cpu_reboot (howto=howto@entry=260,
    bootstr=bootstr@entry=0x0) at
/usr/src/sys/arch/amd64/amd64/machdep.c:671
671                     dumpsys();
(gdb) bt
#0  0xffffffff8068630f in cpu_reboot (howto=howto@entry=260,
    bootstr=bootstr@entry=0x0) at
/usr/src/sys/arch/amd64/amd64/machdep.c:671
#1  0xffffffff808cbce4 in vpanic (fmt=fmt@entry=0xffffffff80dd3d3d "trap",
    ap=ap@entry=0xfffffe8157920d18) at /usr/src/sys/kern/subr_prf.c:340
#2  0xffffffff808cbd9f in panic (fmt=fmt@entry=0xffffffff80dd3d3d "trap")
    at /usr/src/sys/kern/subr_prf.c:256
#3  0xffffffff8091b001 in trap (frame=0xfffffe8157920e20)
    at /usr/src/sys/arch/amd64/amd64/trap.c:298
#4  0xffffffff80100fde in alltraps ()
#5  0xffffffff8070605c in nfs_timer (arg=<optimized out>)
    at /usr/src/sys/nfs/nfs_socket.c:770
#6  0xffffffff80622022 in callout_softclock (v=<optimized out>)
    at /usr/src/sys/kern/kern_timeout.c:736
#7  0xffffffff80616bb8 in softint_execute (l=<optimized out>, s=2,
    si=0xffff80035866a0c0) at /usr/src/sys/kern/kern_softint.c:589
#8  softint_dispatch (pinned=<optimized out>, s=2)
    at /usr/src/sys/kern/kern_softint.c:871
#9  0xffffffff8011412f in Xsoftintr ()


>How-To-Repeat:
You cannot reproduce the crash. The crash occurs randomly and only at high nfs load.
>Fix: