port-alpha/57716: db_panic and db_stacktrace fail to print stack traces

[campbell+netbsd%mumble.net@localhost]

>Number:         57716
>Category:       port-alpha
>Synopsis:       db_panic and db_stacktrace fail to print stack traces
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-alpha-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Nov 21 04:00:01 +0000 2023
>Originator:     Taylor R Campbell
>Release:        current, 10, 9, 8, ...
>Organization:
The NetBSD Alphation
>Environment:
alpha
>Description:
bin/sh/t_patterns (20/940): 3 test cases
    case_matching: [10.629356s] Passed.
    filename_expansion: [ 364.2882718] panic: kernel diagnostic assertion "timo != 0 || intr" failed: file "/tmp/build/2023.11.20.18.03.55-alpha/src/sys/kern/kern_synch.c", line 249 
[ 364.2882718] cpu0: Begin traceback...
[ 364.2882718] alpha trace requires known PC =eject=
[ 364.2882718] cpu0: End traceback...
>How-To-Repeat:
crash NetBSD on alpha
>Fix:
Yes, please!