bin/55423: /bin/csh freezes when some interactive programs are suspended

[kd%panix.com@localhost]

>Number:         55423
>Category:       bin
>Synopsis:       /bin/csh freezes when some interactive programs are suspended
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Jun 26 16:00:00 +0000 2020
>Originator:     Ken Dunlap
>Release:        NetBSD-9
>Organization:
Panix
>Environment:
NetBSD panix1.panix.com 9.0 NetBSD 9.0 (PANIX-XEN-USER) #1: Sun May  3 21:15:18 EDT 2020  root%juggler.panix.com@localhost:/misc/obj64/misc/devel/netbsd/9.0/src/sys/arch/amd64/compile/PANIX-XEN-USER amd64
>Description:
/bin/csh completely freezes when interactive programs are suspended via ^z.  Examples of such programs include newer pythons, irb(ruby), R, erl (the erlang shell), etc.  Killing the suspended program does not unfreeze the shell.  This happens on NetBSD 8.1 also.
>How-To-Repeat:
% exec /bin/csh
% python3.7
% ^z
>Fix: