kern/55178: kernel/t_pty:pty_queue test case fails

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

>Number:         55178
>Category:       kern
>Synopsis:       kernel/t_pty:pty_queue test case fails
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Apr 15 07:20:00 +0000 2020
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current, source date >= 2020.04.05.00.36.25
>Organization:
>Environment:
System: NetBSD
Architecture: i386
Machine: i386
>Description:

The kernel/t_pty:pty_queue test case is currently failing on the
qemu-based TNF i386 testbed:

  http://releng.netbsd.org/b5reports/i386/2020/2020.04.14.05.43.57/test.html#kernel_t_pty_pty_queue

Like the file system test failures of PR 55146, this started during
the period of build breakage that ended with

  2020.04.05.00.36.25 christos src/etc/Makefile 1.443

but unlike those, this one is still failing.

It also fails on amd64 under "qemu -accel nvmm":

  http://www.gson.org/netbsd/bugs/build/amd64/2020/2020.04.12.12.13.52/test.html#kernel_t_pty_pty_queue

I have not seen it fail on real hardware.

>How-To-Repeat:

>Fix: