I upgraded my PC164 system from 1.6.1 to current as of September 17,
and it hung on the 23rd and the 28th. When it's hung, it's still
responsive to pings, but hitting Enter on the console doesn't bring up
a login prompt or echo blank lines. However, Ctrl-Alt-Esc still breaks
into ddb. On the 23rd, the current process was the cyberpower UPS
driver from the sysutils/ups-nut package. On the 28th, it was upsd
from ups-nut (perhaps just a coincidence). I didn't write down the
stack trace from the 23rd, but I believe it was the same (or at least
very similar) to the one from the 28th, which is included below
(transcribed by hand, so I didn't include everything, and there may be
errors):

cpu_Debugger + 0x4
internal_command + 0x190
wskbd_translate + 0x138
wskbd_input + 0x70
pckbd_input + 0x44
pckbcintr + 0x184
alpha_shared_intr_dispatch + 0x6c
sio_iointr + 0x68
interrupt + 0x274
XentInt + 0x1c
--- interrupt (from ipl 0) ---
pmap_changebit + 0x10
pmap_emulate_reference + 0x334
trap + 0x238
XentMM + 0x20
--- memory management fault ---
memcpy + 0x19c
copyout + 0x4c
sys_select + 0x4a4
syscall_plain + 0x138
XentSys + 0x5c
--- syscall (93) ---
--- user mode ---

I know the stack trace from the first hang also included sys_select
and the memory management fault. I don't know if it had the pmap
functions.

Any thoughts, or things I can do to help track this down?

Oh, I tried killing stuff from ddb (including killing init), and
nothing happened when I continued.
-- 
Name: Dave Huang         |  Mammal, mammal / their names are called /
INet: khym@azeotrope.org |  they raise a paw / the bat, the cat /
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