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

[David Holland <dholland-bugs%netbsd.org@localhost>]

The following reply was made to PR bin/55423; it has been noted by GNATS.

From: David Holland <dholland-bugs%netbsd.org@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: bin/55423: /bin/csh freezes when some interactive programs are
 suspended
Date: Mon, 7 Jun 2021 23:01:37 +0000

 On Fri, Jun 26, 2020 at 04:00:01PM +0000, kd%panix.com@localhost wrote:
  > /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.
 
 I can reproduce this and it's not a regression: it also happens with
 csh from 20150101 and 20100101, on a -current kernel from a few months
 ago.
 
 csh's signal handling is extraordinarily delicate and it's as likely
 as not that the problem is in the kernel and not in csh itself. It
 might be instructive to test this with our csh on FreeBSD.
 
 Though since tcsh doesn't exhibit the problem, maybe not.
 
 It's not clear which programs trigger it or why; of the things I have
 lying around that appear to use real gnu libreadline (vs. libedit),
 python 3.8, xindy, and gnuchess trigger it but gawk's debug interface
 doesn't, and nothing I tried that's linked to libedit (e.g. base gdb)
 or curses (e.g. emacs) does.
 
 -- 
 David A. Holland
 dholland%netbsd.org@localhost