bug#40113: 28.0.50; Tramp uses 100% CPU then times out

[Alan Third]

When I try to open "/ssh:warhorse:" Emacs uses 100% CPU and after a minute or
so gives me a timeout error. The buffer *tramp/ssh warhorse* doesn't
exist. Strangely one of my three linux boxes appears to connect OK,
but two time out. I can't see anything different between them.

I can ssh to them OK. I'm using zsh as the shell with the same .zshrc on all
three.

I'm unsure how to debug this problem further.


In GNU Emacs 28.0.50 (build 1, x86_64-apple-darwin18.7.0, NS appkit-1671.60 
Version 10.14.6 (Build 18G3020))
 of 2020-03-16 built on breton.holly.idiocy.org
Repository revision: 9dccaf8a5cdb10dae597345ec3741475477a7d97
Repository branch: master
Windowing system distributor 'Apple', version 10.3.1671
System Description:  Mac OS X 10.14.6

Recent messages:
Auto-saving...done
Auto-saving...done
Auto-saving...done
report-emacs-bug-hook: Wrong type argument: stringp, nil [2 times]
Mark set [2 times]
previous-line: Beginning of buffer [2 times]
scroll-down-command: Beginning of buffer
previous-line: Beginning of buffer
scroll-down-command: Beginning of buffer
Mark set [2 times]

Configured using:
 'configure
 
PKG_CONFIG_PATH=/usr/local/opt/libxml2/lib/pkgconfig:/usr/local/opt/libffi/lib/pkgconfig'

Configured features:
RSVG GLIB NOTIFY KQUEUE ACL GNUTLS LIBXML2 ZLIB TOOLKIT_SCROLL_BARS NS
MODULES THREADS PDUMPER LCMS2 GMP

Important settings:
  value of $LANG: en_GB.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Messages

Minor modes in effect:
  shell-dirtrack-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(help-mode pp shadow sort mail-extr emacsbug message rmc puny dired
dired-loaddefs rfc822 mml easymenu mml-sec epa derived epg epg-config
gnus-util rmail rmail-loaddefs text-property-search mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail
rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils tramp-cmds
tramp-cache tramp-sh tramp tramp-loaddefs trampver tramp-integration
files-x tramp-compat shell pcomplete comint ansi-color ring parse-time
iso8601 time-date ls-lisp format-spec auth-source cl-seq eieio
eieio-core cl-macs eieio-loaddefs cl-loaddefs cl-lib password-cache json
subr-x map seq byte-opt gv bytecomp byte-compile cconv tooltip eldoc
electric uniquify ediff-hook vc-hooks lisp-float-type mwheel term/ns-win
ns-win ucs-normalize mule-util term/common-win tool-bar dnd fontset
image regexp-opt fringe tabulated-list replace newcomment text-mode
elisp-mode lisp-mode prog-mode register page tab-bar menu-bar
rfn-eshadow isearch timer select scroll-bar mouse jit-lock font-lock
syntax facemenu font-core term/tty-colors frame minibuffer cl-generic
cham georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese eucjp-ms cp51932 hebrew greek romanian slovak czech
european ethiopic indian cyrillic chinese composite charscript charprop
case-table epa-hook jka-cmpr-hook help simple abbrev obarray
cl-preloaded nadvice loaddefs button faces cus-face macroexp files
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote threads kqueue cocoa ns
lcms2 multi-tty make-network-process emacs)

Memory information:
((conses 16 67324 16837)
 (symbols 48 8141 0)
 (strings 32 24277 2073)
 (string-bytes 1 888909)
 (vectors 16 14087)
 (vector-slots 8 174757 17740)
 (floats 8 42 90)
 (intervals 56 521 54)
 (buffers 1000 16))

-- 
Alan Third