locking against myself panic (cprng_strongreseed, filt_rndread)

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

I got the following panic on a mostly idle 6.1/amd64:

Mutex error: mutex_vector_enter: locking against myself

lock address : 0xfffffe82f9174980
current cpo  :                  1
current lwp  : 0xfffffe811d2e9900
owner field  : 0xfffffe811d2e9900 wait/spin:                0/0

panic: lock error
fatal breakpint trap in supervisor mode
trap type 1 code 0 rip ffffffff80179c1d cd 8 rflags 246 cr2  ffff80011fc4f000 cpl 8 rsp fffffe811d2bba30
Stopped in pid 0.20 (system) at netbsd:breakpoint+9x5:	leave
db{1}> bt
breakpoint() at netbsd:breakpoint+0x5
vpanic() at netbsd:vpanic+0x1f2
printf_nolog() at netbsd:printf_nolog
lockdebug_abort() at netbsd:lockdebug_abort+0x3a
mutex_vector_enter() at netbsd:mutex_vector_enter+0x3df
filt_rndread() at netbsd:filt_rndread+0x16
knote() at netbsd:knote+0x33
selnotify() at netbsd:selnotify+0x24
cprng_strong_doreseed() at netbsd:cprng_strong_doreseed+0xbd
cprng_strong_reseed() at netbsd:cprng_strong_reseed+0x2d
rnd_wakeup_readers() at netbsd:rnd_wakeup_readers+0x171
callout_softclock() at netbsd:callout_softclock+0x174
softint_dispatch() at netbsd:softint_dispatch+0x7b
DDB lost frame for netbsd:Xsoftintr+0x4f, trying 0xfffffe811d2bbd70
Xsoftintr() at netbsd:Xsoftintr+0x4f
--- interrupt ---
0:
db{1}> show lock fffffe82f917490
Sorry, kernel not built with the LOCKDEBUG option.
db{1} reboot 0x100

dumping to dev 18,1 offset 1735
dump 44 43 42 41 40 39 38 37 

and then the machine got stuck. It's a development server, so I can leave it stuck until tomorrow in case someone wants me to examine anything in particular.