kern/51056: reader-writer lock error

[martin%NetBSD.org@localhost]

>Number:         51056
>Category:       kern
>Synopsis:       reader-writer lock error
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Apr 09 08:00:00 +0000 2016
>Originator:     Martin Husemann
>Release:        NetBSD 7.99.27
>Organization:
The NetBSD Foundation, Inc.
>Environment:
System: NetBSD night-owl.duskware.de 7.99.27 NetBSD 7.99.27 (NIGHT-OWL) #402: Tue Apr 5 16:22:09 CEST 2016 martin%night-owl.duskware.de@localhost:/usr/src/sys/arch/amd64/compile/NIGHT-OWL amd64
Architecture: x86_64
Machine: amd64
>Description:

Seen this twice since updating to 7.99.27:

#9  0xffffffff806ef0c3 in vpanic (
    fmt=fmt@entry=0xffffffff80cc8940 "lock error: %s: %s: %s: lock %p cpu %d lwp %p", ap=ap@entry=0xfffffe80bf7a6c58) at ../../../../kern/subr_prf.c:340
#10 0xffffffff806ef180 in panic (
    fmt=fmt@entry=0xffffffff80cc8940 "lock error: %s: %s: %s: lock %p cpu %d lwp %p") at ../../../../kern/subr_prf.c:258
#11 0xffffffff806e7b26 in lockdebug_abort (lock=0xfffffe8135c46888, 
    ops=ops@entry=0xffffffff80faff30 <rwlock_lockops>, 
    func=func@entry=0xffffffff80bc5bc0 <__func__.6032> "rw_vector_enter", 
    msg=msg@entry=0xffffffff80cc321d "locking against myself")
    at ../../../../kern/subr_lockdebug.c:867
#12 0xffffffff806c1398 in rw_abort (rw=rw@entry=0xfffffe8135c46888, 
    func=func@entry=0xffffffff80bc5bc0 <__func__.6032> "rw_vector_enter", 
    msg=msg@entry=0xffffffff80cc321d "locking against myself")
    at ../../../../kern/kern_rwlock.c:192
#13 0xffffffff806c186b in rw_vector_enter (rw=0xfffffe8135c46888, op=RW_READER)
    at ../../../../kern/kern_rwlock.c:341
#14 0xffffffff804eecfd in in6_lltable_lookup (llt=<optimized out>, 
    flags=<optimized out>, l3addr=<optimized out>)
    at ../../../../netinet6/in6.c:2487
#15 0xffffffff80505c08 in lla_lookup (l3addr=0xfffffe80bf7a6dbc, flags=0, 
    llt=<optimized out>) at ../../../../net/if_llatbl.h:295
#16 nd6_lookup (addr6=<optimized out>, ifp=0xffff800007006d30, 
    wlock=wlock@entry=false) at ../../../../netinet6/nd6.c:864
#17 0xffffffff8050ad26 in nd6_is_llinfo_probreach (dr=<optimized out>)
    at ../../../../netinet6/nd6_rtr.c:113
#18 find_pfxlist_reachable_router (pr=0xfffffe8107c0a158)
    at ../../../../netinet6/nd6_rtr.c:1384
#19 0xffffffff8050b8c6 in pfxlist_onlink_check ()
    at ../../../../netinet6/nd6_rtr.c:1417
#20 0xffffffff805052a9 in nd6_free (ln=0xfffffe8135c46788, gc=0)
    at ../../../../netinet6/nd6.c:1177
#21 0xffffffff8050590d in nd6_llinfo_timer (arg=0xfffffe8135c46788)
    at ../../../../netinet6/nd6.c:490
#22 0xffffffff806d29a1 in callout_softclock (v=<optimized out>)
    at ../../../../kern/kern_timeout.c:743
#23 0xffffffff806c73b4 in softint_execute (l=<optimized out>, s=2, 
    si=0xffff800045e710c0) at ../../../../kern/kern_softint.c:589
#24 softint_dispatch (pinned=<optimized out>, s=2)
    at ../../../../kern/kern_softint.c:871
#25 0xffffffff80113f7f in Xsoftintr ()

netbsd.gdb and crash dump available on request.


>How-To-Repeat:
just happens randomly, nothing special

>Fix:
n/a