kern/59727: wsmux changes in April 2025 seem to have broken kqueue on wsmux

[nia%pkgsrc.org@localhost]

>Number:         59727
>Category:       kern
>Synopsis:       wsmux changes in April 2025 seem to have broken kqueue on wsmux
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Oct 26 09:40:00 +0000 2025
>Originator:     nia
>Release:        -11, -current...
>Organization:
The NetBSD Foundation
>Environment:
NetBSD siphon 11.99.3 NetBSD 11.99.3 (SIPHON) #13: Thu Oct 23 23:06:13 CEST 2025  nia@siphon:/encrypt/obj/sys/arch/amd64/compile/SIPHON amd64
>Description:
System panicked: kernel diagnostic assertion "sc->sc_base.me_evp == NULL" failed: file "/encrypt/src/sys/dev/wscons/wsmux.c", line 592 wsmuxkqfilter: not open

Backtrace from time of crash is available.
crash> bt
vmx_insn_failinvalid() at 0
kern_reboot() at kern_reboot+0x5f
vpanic() at vpanic+0x193
kern_assert() at __x86_indirect_thunk_rax
wsmuxkqfilter() at wsmuxkqfilter+0x78
cdev_kqfilter() at cdev_kqfilter+0x7f
spec_kqfilter() at spec_kqfilter+0x71
VOP_KQFILTER() at VOP_KQFILTER+0x5c
kevent1() at kevent1+0xfe5
sys___kevent100() at sys___kevent100+0x35
syscall() at syscall+0x9d
--- syscall (number 501) ---
syscall+0x9d:
>How-To-Repeat:
install wm/velox, follow the instructions in MESSAGE to run it, observe
instant panic
>Fix:
revert wsmux changes from 2025 that replaced diagnostic checks with
asserts