kern/55846: Kernel now panics during kernel/t_lock:lock test case

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         55846
>Category:       kern
>Synopsis:       Kernel now panics during kernel/t_lock:lock test case
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Dec 06 15:30:00 +0000 2020
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current
>Organization:
  
>Environment:
System: NetBSD
Architecture: i386
Machine: i386
>Description:

On the TNF testbed, the system under test now panics when running
the ATF test, specifically the "lock" test case of the kernel/t_lock
test.  This happens on at least i386, sparc, and evbarm-aarch64,
so it's probably MI.

The problem started during the period of build breakage that started
with:

  2020.12.05.18.17.01 thorpej src/sys/kern/init_main.c 1.534
  2020.12.05.18.17.01 thorpej src/sys/kern/kern_clock.c 1.143
  2020.12.05.18.17.01 thorpej src/sys/kern/kern_exec.c 1.504
  2020.12.05.18.17.01 thorpej src/sys/kern/kern_exit.c 1.291
  2020.12.05.18.17.01 thorpej src/sys/kern/kern_time.c 1.207
  2020.12.05.18.17.01 thorpej src/sys/sys/param.h 1.681
  2020.12.05.18.17.01 thorpej src/sys/sys/proc.h 1.368
  2020.12.05.18.17.01 thorpej src/sys/sys/timevar.h 1.45

and ended with:

  2020.12.06.09.03.29 skrll src/sys/rump/librump/rumpkern/rump.c 1.351

Logs from i386:

  http://releng.netbsd.org/b5reports/i386/commits-2020.12.html#2020.12.06.09.03.29

>How-To-Repeat:

Run the ATF tests.

>Fix: