kern/59339: heartbeat watchdog fires since 10.99.14

[prlw1%cam.ac.uk@localhost]

>Number:         59339
>Category:       kern
>Synopsis:       heartbeat watchdog fires since 10.99.14
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Apr 21 19:40:00 +0000 2025
>Originator:     Patrick Welche
>Release:        NetBSD-10.99.14/amd64
>Organization:
>Environment:
src of 8:05 UTC 17 April 2025
>Description:
Possibly related to other hangs in the thread
https://mail-index.netbsd.org/current-users/2025/04/17/msg046436.html

A formerly stable laptop has had two heartbeat panics

System panicked: cpu0: softints stuck for 16 seconds
crash> bt
end() at 0
kern_reboot() at kern_reboot+0x93
vpanic() at vpanic+0x16b
panic() at vprintf
heartbeat() at heartbeat+0x1f2
hardclock() at hardclock+0x9c
Xresume_lapic_ltimer() at Xresume_lapic_ltimer+0x1e
--- interrupt ---
mutex_spin_exit() at mutex_spin_exit+0x5a
callout_softclock() at callout_softclock+0xad
softint_dispatch() at softint_dispatch+0x8f
crash> ps
PID     LID S CPU     FLAGS       STRUCT LWP *               NAME WAIT
2917 > 2917 7   0   8060000   ffff8052e4a14000                tar
0    >    5 7   0       200   ffff8055abee1c00          softclk/0



System panicked: cpu1[27 softclk/1]: heart stopped beating
crash> bt
end() at 0
kern_reboot() at kern_reboot+0x93
vpanic() at vpanic+0x16b
panic() at vprintf
defibrillator() at defibrillator+0x6b
ipi_msg_cpu_handler() at ipi_msg_cpu_handler+0x50
ipi_cpu_handler() at ipi_cpu_handler+0x73
x86_ipi_handler() at x86_ipi_handler+0x6b
Xresume_lapic_ipi() at Xresume_lapic_ipi+0x18
--- interrupt ---
getnanotime() at getnanotime+0x53
tshzto() at tshzto+0x1b
itimer_callout() at itimer_callout+0xb1
callout_softclock() at callout_softclock+0xad
softint_dispatch() at softint_dispatch+0x8f
crash: _kvm_kvatop(ffff9704a471b0b8)
crash: kvm_read(0xffff9704a471b0b8, 8): invalid translation (invalid PTE)
crash> ps
PID     LID S CPU     FLAGS       STRUCT LWP *               NAME WAIT
1266 > 1266 7   0   8020100   ffff81f02e1a7800               cron
992  >  992 7   1   8020000   ffff81f026788c00                  X
857  >  857 7   2   8020100   ffff81f027510400                xdm
0    >   27 7   1       200   ffff81f020f56400          softclk/1


I can't think of any similarities between the two situations.
>How-To-Repeat:
Not obviously reproducible, e.g., the untar during which the first
hang happened succeeded on reboot. firefox was running the first, not
the second, in fact not much was going on in the second.
>Fix: