Panic under npf_conndb_gc on netbsd-10 amd64

[Paul Ripke <stix%stix.id.au@localhost>]

I've had two hangs and now one panic in the last 2 weeks of running
netbsd-10, all triggered during or just after /etc/daily. Also, there's
unfortunately no dump - I have raid0b configured as dumpdev, but there's
nothing there.

Aug 19 05:36:10 slave /netbsd: [ 197499.3520506] uvm_fault(0xffffffff815500e0, 0x0, 2) -> e
Aug 19 05:36:10 slave /netbsd: [ 197499.3520506] fatal page fault in supervisor mode
Aug 19 05:36:10 slave /netbsd: [ 197499.3520506] trap type 6 code 0x2 rip 0xffffffff80bb93af cs 0x8 rflags 0x10286 cr2 0 ilevel 0x4 rsp 0xffff90044c6ded80
Aug 19 05:36:10 slave /netbsd: [ 197499.3520506] curlwp 0xffff844b73bc9040 pid 0.190 lowest kstack 0xffff90044c6da2c0
Aug 19 05:36:10 slave /netbsd: [ 197499.3520506] panic: trap
Aug 19 05:36:10 slave /netbsd: [ 197499.3520506] cpu0: Begin traceback...
Aug 19 05:36:10 slave /netbsd: [ 197499.3520506] vpanic() at netbsd:vpanic+0x183
Aug 19 05:36:10 slave /netbsd: [ 197499.3530509] panic() at netbsd:panic+0x3c
Aug 19 05:36:10 slave /netbsd: [ 197499.3540505] trap() at netbsd:trap+0xb27
Aug 19 05:36:10 slave /netbsd: [ 197499.3540505] --- trap (number 6) ---
Aug 19 05:36:10 slave /netbsd: [ 197499.3550505] stage_mem_gc() at netbsd:stage_mem_gc+0x2c
Aug 19 05:36:10 slave /netbsd: [ 197499.3550505] thmap_del() at netbsd:thmap_del+0x58d
Aug 19 05:36:10 slave /netbsd: [ 197499.3560505] npf_conndb_remove() at netbsd:npf_conndb_remove+0x39
Aug 19 05:36:10 slave /netbsd: [ 197499.3570504] npf_conn_remove() at netbsd:npf_conn_remove+0x97
Aug 19 05:36:10 slave /netbsd: [ 197499.3570504] npf_conndb_gc() at netbsd:npf_conndb_gc+0x33f
Aug 19 05:36:10 slave /netbsd: [ 197499.3580504] npf_worker() at netbsd:npf_worker+0x81
Aug 19 05:36:10 slave /netbsd: [ 197499.3580504] cpu0: End traceback...
Aug 19 05:36:10 slave /netbsd: 
Aug 19 05:36:10 slave /netbsd: [ 197499.3590513] dumping to dev 18,1 (offset=8, size=4181325):
Aug 19 05:36:10 slave /netbsd: [ 197499.3590513] dump

-- 
Paul Ripke
"Great minds discuss ideas, average minds discuss events, small minds
 discuss people."
-- Disputed: Often attributed to Eleanor Roosevelt. 1948.