kern/58171: pckbport is not MP-safe

[campbell+netbsd%mumble.net@localhost]

>Number:         58171
>Category:       kern
>Synopsis:       pckbport is not MP-safe
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Apr 17 22:10:00 +0000 2024
>Originator:     Taylor R Campbell
>Release:        current, 10, 9, 8
>Organization:
The NetBS/2 Foundation
>Environment:
>Description:
pckbport and all associated drivers -- pckbd(4), pms(4), the sub-drivers for alps/elantech/synaptics -- are not MP-safe: they run with the kernel lock.

This is bad for interactivity when _any other_ legacy kernel-locked subsystem hogs _any_ CPU.

(Note: wscons/wskbd/wsmouse/wsevent also have the same problem, but let's use a separate PR to track those.)
>How-To-Repeat:
find something that hogs the kernel lock for longer than a few milliseconds and try to type or mouse around while using it
>Fix:
Yes, please!