shutdown drops into db

[Patrick Welche <prlw1%cam.ac.uk@localhost>]

Having just read

  http://mail-index.netbsd.org/port-i386/2013/03/18/msg003065.html

"shutdown -r now" on a vaguely current/amd64 box gave:

db{0}> bt
breakpoint() at netbsd:breakpoint+0x5
comintr() at netbsd:comintr+0x51d
Xintr_ioapic_edge7() at netbsd:Xintr_ioapic_edge7+0xea
--- interrupt ---
kpreempt_disabled() at netbsd:kpreempt_disabled+0x17
pmap_deactivate() at netbsd:pmap_deactivate+0x15
mi_switch() at netbsd:mi_switch+0x329
sleepq_block() at netbsd:sleepq_block+0xa4
mtsleep() at netbsd:mtsleep+0x110
uvn_findpage() at netbsd:uvn_findpage+0x106
uvn_findpages() at netbsd:uvn_findpages+0x76
genfs_getpages() at netbsd:genfs_getpages+0x523
VOP_GETPAGES() at netbsd:VOP_GETPAGES+0x4f
uvm_fault_internal() at netbsd:uvm_fault_internal+0xcab
trap() at netbsd:trap+0x4fa
--- trap (number 6) ---
7f7ff6038eea:

It is possible that I got that by plugging in a serial console, then
again the reason for plugging in the serial console was to work out
why it didn't shutdown. I can "continue", but the box remains pingable and
still doesn't shutdown. Breaking into ddb again shows:

db{0}> c
~fatal breakpoint trap in supervisor mode
trap type 1 code 0 rip ffffffff801e15cd cs 8 rflags 202 cr2 7f7ff6038eea ilevel 
8 rsp fffffe8006cfd9e8
curlwp 0xfffffe80bde69680 pid 0.67 lowest kstack 0xfffffe8006cfa000
Stopped in pid 0.67 (system) at netbsd:breakpoint+0x5:  leave
db{0}> bt
breakpoint() at netbsd:breakpoint+0x5
comintr() at netbsd:comintr+0x51d
Xintr_ioapic_edge7() at netbsd:Xintr_ioapic_edge7+0xea
--- interrupt ---
uvmpd_dropswap() at netbsd:uvmpd_dropswap+0x3f
uvm_pageout() at netbsd:uvm_pageout+0x286

(DIAGNOSTIC kernel but no LOCKDEBUG)

Cheers,

Patrick