kern/55030: nd6_llinfo_timer causes locking against myself

[christos%netbsd.org@localhost]

>Number:         55030
>Category:       kern
>Synopsis:       nd6_llinfo_timer causes locking against myself
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Feb 28 17:50:00 +0000 2020
>Originator:     Christos Zoulas
>Release:        NetBSD 9.99.48
>Organization:
	Entropy Anonymous
>Environment:
System: NetBSD quasar.astron.com 9.99.48 NetBSD 9.99.48 (QUASAR) #76: Thu Feb 27 22:02:36 EST 2020 christos%quasar.astron.com@localhost:/usr/src/sys/arch/amd64/compile/QUASAR amd64
Architecture: x86_64
Machine: amd64
>Description:
path throu in6_lltable_lookup tries to lock lle entry locked by
nd6_llinfo_timer.
>How-To-Repeat:
Normal running of the network
>Fix:

Wait for timer processing to finish before taking the lock (blocking
on softint?)
Panic:
    https://www.zoulas.com/~christos/NetBSD/nd6.png