kern/60595: System lockup using gdb(1) on kernel with DEBUG+LOCKDEBUG

["rvp%SDF.ORG@localhost via gnats" <gnats-admin%NetBSD.org@localhost>]

>Number:         60595
>Category:       kern
>Synopsis:       System lockup using gdb(1) on kernel with DEBUG+LOCKDEBUG
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Aug 15 08:40:00 +0000 2026
>Originator:     RVP
>Release:        11.99.7
>Organization:
>Environment:
NetBSD CoreBook.local 11.99.7 NetBSD 11.99.7 (COREBOOK_DIAG) #0: Sat Aug 15 04:21:15 UTC 2026  bld@CoreBook.local:/tmp/obj/usr/src/sys/arch/amd64/compile/COREBOOK_DIAG amd64
>Description:
On a kernel compiled with DEBUG and LOCKDEBUG, running gdb(1) on any
trivial program locks up the whole system.
>How-To-Repeat:
As any user on a kernel with DEBUG & LOCKDEBUG:

```
$ echo 'int main(void) { return 0; }' > t.c
$ cc -o t t.c
$ gdb t
(gdb) run
```

System locks up completely. Must power off to recover.
>Fix:
No idea.