GNU bug report logs - #79014
31.0.50; igc: infinite loop

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Óscar Fuentes <oscarfv <at> eclipso.eu>
To: bug-gnu-emacs <at> gnu.org
Subject: 31.0.50; igc: infinite loop
Date: Mon, 14 Jul 2025 13:15:43 +0200

On a long-lived emacs session (two weeks of intensive use), while
reverting a versioned file with C-x v u (something that I did multiple
times before on the same session) Emacs entered an infinite loop using
100% CPU, ignoring C-g and SIGUSR2 and had to be killed eventually after
attaching gdb and obtaining the backtraces below.

#0  truncate_undo_list (b=b <at> entry=0x7fb33b464b18) at ../../emacs/src/lisp.h:1534
        list = <optimized out>
        prev = <optimized out>
        next = <optimized out>
        last_boundary = 0x0
        size_so_far = 20445947
        count = {bytes = <optimized out>}
        undo_outer_limit = <optimized out>
#1  0x00005596d35701d9 in compact_buffer (buffer=buffer <at> entry=0x7fb33b464b18)
    at ../../emacs/src/buffer.c:1874
#2  0x00005596d36669e2 in buffer_step (it=<synthetic pointer>) at ../../emacs/src/igc.c:4051
        buf = 0x7fb33b464b1d
        b = 0x7fb33b464b18
#3  igc_on_idle () at ../../emacs/src/igc.c:4083
        work_done = <optimized out>
        clock = {expire = <optimized out>}
        buffer_it = {alist = <optimized out>, buf = <optimized out>}
#4  0x00005596d354f2b5 in timer_check_2 (timers=<optimized out>, idle_timers=<optimized out>)
    at ../../emacs/src/keyboard.c:4722
        now = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
        idleness_now = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
        now = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
        idleness_now = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
        funcall = <optimized out>
        chosen_timer = <optimized out>
        timer = <optimized out>
        idle_timer = <optimized out>
--Type <RET> for more, q to quit, c to continue without paging--
        difference = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
        timer_difference = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
        idle_timer_difference = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
        ripe = <optimized out>
        timer_ripe = <optimized out>
        idle_timer_ripe = <optimized out>
        timer_time = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
        idle_timer_time = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
        count = {bytes = <optimized out>}
        old_deactivate_mark = <optimized out>
#5  timer_check () at ../../emacs/src/keyboard.c:4891
        nexttime = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
        timers = 0x7fb256c7dc73
        idle_timers = <optimized out>
        tem = <optimized out>
#6  0x00005596d354f7e5 in readable_events (flags=flags <at> entry=3) at ../../emacs/src/keyboard.c:3618
#7  0x00005596d354f9c0 in get_input_pending (flags=flags <at> entry=3) at ../../emacs/src/keyboard.c:8007
#8  0x00005596d354fad5 in Finput_pending_p (check_timers=0x38) at ../../emacs/src/keyboard.c:11799
#9  0x00007fb32f4ed5b2 in F7369742d666f72_sit_for_0 ()
    at /home/oscar/dev/emacs/igc/build/src/../native-lisp/31.0.50-61e73da1/preloaded/subr-13adf6a6-dbedbcf7.eln
#10 0x00005596d35d6a0c in Ffuncall (nargs=2, args=0x7fff3751ec00) at ../../emacs/src/eval.c:3195
        count = {bytes = <optimized out>}
        val = <optimized out>
#11 0x00007fb32e40648e in F646973706c61792d7761726e696e67_display_warning_0 ()
    at /home/oscar/.emacs.d/eln-cache/31.0.50-61e73da1/warnings-28e75f4d-f0ade81c.eln
#12 0x00005596d35d6a0c in Ffuncall (nargs=4, args=0x7fff3751ee00) at ../../emacs/src/eval.c:3195
--Type <RET> for more, q to quit, c to continue without paging--
        count = {bytes = <optimized out>}
        val = <optimized out>
#13 0x00007fb32f243db7 in F756e646f2d6f757465722d6c696d69742d7472756e63617465_undo_outer_limit_truncate_0
    ()
    at /home/oscar/dev/emacs/igc/build/src/../native-lisp/31.0.50-61e73da1/preloaded/simple-fab5b0cf-9e866eaa.eln
#14 0x00005596d35d6a0c in Ffuncall (nargs=nargs <at> entry=2, args=args <at> entry=0x7fff3751ee80)
    at ../../emacs/src/eval.c:3195
        count = {bytes = <optimized out>}
        val = <optimized out>
#15 0x00005596d35ae9ed in truncate_undo_list (b=b <at> entry=0x7fb33b464b18) at ../../emacs/src/undo.c:366
        tem = <optimized out>
        list = <optimized out>
        prev = <optimized out>
        next = <optimized out>
        last_boundary = 0x0
        size_so_far = <optimized out>
        count = {bytes = <optimized out>}
        undo_outer_limit = <optimized out>
#16 0x00005596d35701d9 in compact_buffer (buffer=buffer <at> entry=0x7fb33b464b18)
    at ../../emacs/src/buffer.c:1874
#17 0x00005596d36669e2 in buffer_step (it=<synthetic pointer>) at ../../emacs/src/igc.c:4051
        buf = 0x7fb33b464b1d
        b = 0x7fb33b464b18
#18 igc_on_idle () at ../../emacs/src/igc.c:4083
        work_done = <optimized out>
        clock = {expire = <optimized out>}
--Type <RET> for more, q to quit, c to continue without paging--
        buffer_it = {alist = <optimized out>, buf = <optimized out>}
#19 0x00005596d354f2b5 in timer_check_2 (timers=<optimized out>, idle_timers=<optimized out>)
    at ../../emacs/src/keyboard.c:4722
        now = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
        idleness_now = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
        now = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
        idleness_now = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
        funcall = <optimized out>
        chosen_timer = <optimized out>
        timer = <optimized out>
        idle_timer = <optimized out>
        difference = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
        timer_difference = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
        idle_timer_difference = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
        ripe = <optimized out>
        timer_ripe = <optimized out>
        idle_timer_ripe = <optimized out>
        timer_time = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
        idle_timer_time = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
        count = {bytes = <optimized out>}
        old_deactivate_mark = <optimized out>
#20 timer_check () at ../../emacs/src/keyboard.c:4891
        nexttime = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
        timers = 0x7fb256c795b3
        idle_timers = <optimized out>
        tem = <optimized out>



(gdb) xbacktrace
"sit-for" (0x3751ec08)
"display-warning" (0x3751ee08)
"undo-outer-limit-truncate" (0x3751ee88)
"sit-for" (0x3751f1c8)
"display-warning" (0x3751f3c8)
"undo-outer-limit-truncate" (0x3751f448)
"sit-for" (0x3751f788)
"display-warning" (0x3751f988)
"undo-outer-limit-truncate" (0x3751fa08)
"sit-for" (0x3751fd48)
"display-warning" (0x3751ff48)
"undo-outer-limit-truncate" (0x3751ffc8)
"sit-for" (0x37520308)
"display-warning" (0x37520508)
"undo-outer-limit-truncate" (0x37520588)
"sit-for" (0x375208c8)
"display-warning" (0x37520ac8)
"undo-outer-limit-truncate" (0x37520b48)
"sit-for" (0x37520e88)
"display-warning" (0x37521088)
"undo-outer-limit-truncate" (0x37521108)
"sit-for" (0x37521448)
"display-warning" (0x37521648)
"undo-outer-limit-truncate" (0x375216c8)
"sit-for" (0x37521a08)
"display-warning" (0x37521c08)
"undo-outer-limit-truncate" (0x37521c88)



In GNU Emacs 31.0.50 (build 1, x86_64-pc-linux-gnu, X toolkit, cairo
 version 1.18.4) of 2025-06-29 built on zen
Repository revision: 1c19182e28e90b619a4c3d5553e3b5ae03eccd12
Repository branch: feature/igc
Windowing system distributor 'The X.Org Foundation', version 11.0.12101016
System Description: Debian GNU/Linux 13 (trixie)

Configured using:
 'configure 'CPPFLAGS=-O2 -fno-omit-frame-pointer -g3'
 CPPFLAGS=-I/home/oscar/dev/include/mps
 LDFLAGS=-L/home/oscar/dev/other/mps/code --with-native-compilation
 --with-tree-sitter --without-toolkit-scroll-bars --with-x-toolkit=lucid
 --with-modules --without-imagemagick --with-mps=yes'

Configured features:
CAIRO FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ JPEG LIBOTF
LIBSELINUX LIBXML2 MODULES MPS NATIVE_COMP NOTIFY INOTIFY PDUMPER PNG
RSVG SECCOMP SOUND SQLITE3 THREADS TIFF TREE_SITTER WEBP X11 XAW3D XDBE
XIM XPM LUCID ZLIB

Important settings:
  value of $LANG: C
  locale-coding-system: nil

Major mode: Lisp Interaction

Minor modes in effect:
  window-highlight-mode: t
  xterm-mouse-mode: t
  treemacs-filewatch-mode: t
  treemacs-follow-mode: t
  treemacs-git-mode: t
  treemacs-fringe-indicator-mode: t
  org-roam-db-autosync-mode: t
  fancy-compilation-mode: t
  diff-hl-flydiff-mode: t
  diff-hl-mode: t
  difftastic-bindings-mode: t
  global-git-commit-mode: t
  pulsar-global-mode: t
  pulsar-mode: t
  evil-owl-mode: t
  enhanced-evil-paredit-mode: t
  evil-local-mode: t
  key-chord-mode: t
  paredit-mode: t
  server-mode: t
  display-fill-column-indicator-mode: t
  vertico-multiform-mode: t
  marginalia-mode: t
  vertico-mode: t
  which-key-mode: t
  global-anzu-mode: t
  anzu-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  minibuffer-regexp-mode: t
  column-number-mode: t
  line-number-mode: t
  indent-tabs-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
/home/oscar/elisp/singles/flx hides /home/oscar/.emacs.d/elpa/flx-20240205.356/flx
/home/oscar/elisp/magit/lisp/magit-section hides /home/oscar/.emacs.d/elpa/magit-section-20250704.2300/magit-section
/home/oscar/elisp/singles/which-key hides /home/oscar/dev/emacs/igc/emacs/lisp/which-key

Features:
(shadow sort mail-extr emacsbug help-fns radix-tree vertico-directory
mule-util vertico-sort fussy window-highlight
solarized-selenized-dark-theme solarized-selenized-light-theme
solarized-palettes solarized solarized-faces xt-mouse term/xterm xterm
meteo-radar lsp-dart lsp-dart-commands lsp-dart-flutter-widget-guide
lsp-dart-flutter-fringe-colors lsp-dart-flutter-colors lsp-dart-outline
lsp-dart-code-lens lsp-lens lsp-dart-test-tree lsp-treemacs
lsp-treemacs-generic lsp-treemacs-themes treemacs-treelib treemacs
treemacs-header-line treemacs-compatibility treemacs-mode
treemacs-bookmarks treemacs-tags treemacs-interface treemacs-persistence
treemacs-filewatch-mode treemacs-follow-mode treemacs-rendering
treemacs-annotations treemacs-async treemacs-workspaces treemacs-dom
treemacs-visuals treemacs-fringe-indicator treemacs-faces treemacs-icons
treemacs-scope treemacs-themes treemacs-core-utils pfuture hl-line
treemacs-logging treemacs-customization treemacs-macros
lsp-dart-test-output lsp-dart-test-support lsp-dart-dap
lsp-dart-devtools lsp-dart-flutter-daemon jsonrpc dap-utils dom xml
dap-mode dap-tasks dap-launch lsp-docker yaml posframe dap-overlays
lsp-dart-closing-labels lsp-dart-utils lsp-dart-protocol lsp-mode
lsp-protocol tree-widget spinner network-stream nsm markdown-mode lv f
flymake flycheck lp0-ts-mode lp0-mode symbol-overlay company-ctags
find-file company-fuzzy ht company aggressive-indent deft orgit
emacsql-sqlite-builtin org-roam-migrate org-roam-log org-roam-mode
org-roam-capture org-roam-id org-roam-node org-roam-db org-roam-utils
org-roam-compat org-roam org-attach emacsql-sqlite emacsql
emacsql-compiler org-noter org-element org-persist org-id
org-element-ast inline avl-tree org-protocol org-capture org-refile
org-crypt org ob ob-tangle ob-ref ob-lob ob-table ob-exp org-macro
org-src sh-script smie treesit executable ob-comint org-pcomplete
org-list org-footnote org-faces org-entities noutline outline
ob-emacs-lisp ob-core ob-eval org-cycle org-table org-keys oc
org-loaddefs find-func etags-select etags fileloop generator xref
project ol org-fold org-fold-core org-compat org-version org-macs
cond-star fancy-compilation ffap diff-hl-flydiff diff-hl log-view
difftastic-bindings difftastic view magit-bookmark bookmark git-rebase
magit-dired magit-extras magit-sparse-checkout magit-gitignore
magit-ediff ediff magit-subtree magit-patch magit-submodule magit-blame
magit-stash magit-reflog magit-bisect magit-push magit-pull magit-fetch
magit-clone magit-remote magit-commit magit-sequence magit-notes
magit-worktree magit-tag magit-merge magit-branch magit-reset
magit-files magit-refs magit-status magit magit-repos magit-apply
magit-wip magit-log magit-diff smerge-mode diff git-commit magit-core
magit-autorevert autorevert filenotify magit-margin magit-transient
magit-process with-editor shell pcomplete magit-mode transient magit-git
magit-base which-func imenu vc-git files-x vc-dir ewoc vc vc-dispatcher
magit-section benchmark cursor-sensor crm llama pulsar pulse color
evil-owl format-spec buffer-flip enhanced-evil-paredit evil-anzu evil
evil-keybindings evil-integration evil-maps evil-commands evil-digraphs
reveal evil-jumps evil-command-window evil-types evil-search evil-ex
evil-macros evil-repeat evil-states evil-core evil-common rect evil-vars
mini-echo mini-echo-segments let-alist hide-mode-line face-remap wgrep
grep ag vc-svn find-dired s dash key-chord comp comp-cstr comp-run
comp-common cmake-mode rx rst compile comint ansi-osc ansi-color
paredit-menu paredit edmacro kmacro server yasnippet lisp-mnt psvn
wid-edit log-edit message sendmail yank-media puny rfc822 mml mml-sec
epa derived epg rfc6068 epg-config gnus-util text-property-search
time-date mm-decode mm-bodies mm-encode mail-parse rfc2231 rfc2047
rfc2045 mm-util ietf-drums mail-prsvr mailabbrev mail-utils gmm-utils
mailheader pcvs-util add-log diff-mode track-changes pp elp ediff-merg
ediff-mult ediff-wind ediff-diff ediff-help ediff-init ediff-util dired
dired-loaddefs display-fill-column-indicator vertico-multiform
marginalia vertico flx-rs-core flx-rs flx goto-chg avy ring
highlight-parentheses ws-butler which-key diminish cl anzu easy-mmode
thingatpt tmr pcase compat solar cal-dst cal-menu calendar cal-loaddefs
finder-inf advice cl-extra help-mode warnings disp-table
apropospriate-theme-autoloads company-posframe-autoloads
company-autoloads consult-flycheck-autoloads consult-lsp-autoloads
consult-org-roam-autoloads corfu-autoloads deadgrep-autoloads
diff-hl-autoloads eat-autoloads ellama-autoloads
embark-consult-autoloads consult-autoloads embark-autoloads
flutter-autoloads flycheck-autoloads fussy-autoloads flx-autoloads
groovy-mode-autoloads llm-autoloads lsp-dart-autoloads
dart-mode-autoloads dap-mode-autoloads bui-autoloads
lsp-docker-autoloads lsp-treemacs-autoloads lsp-ui-autoloads
lsp-mode-autoloads f-autoloads marginalia-autoloads
markdown-mode-autoloads org-roam-autoloads magit-section-autoloads
llama-autoloads emacsql-autoloads plz-event-source-autoloads
plz-media-type-autoloads plz-autoloads pomm-autoloads alert-autoloads
log4e-autoloads gntp-autoloads spinner-autoloads swiper-autoloads
ivy-autoloads symbol-overlay-autoloads treemacs-autoloads cfrs-autoloads
posframe-autoloads ht-autoloads hydra-autoloads lv-autoloads
pfuture-autoloads ace-window-autoloads avy-autoloads s-autoloads info
dash-autoloads vertico-autoloads wgrep-ag-autoloads
wgrep-deadgrep-autoloads wgrep-autoloads yaml-autoloads package
browse-url xdg url url-proxy url-privacy url-expand url-methods
url-history url-cookie generate-lisp-file url-domsuf url-util mailcap
url-handlers url-parse auth-source cl-seq eieio eieio-core cl-macs icons
password-cache json subr-x map byte-opt gv bytecomp byte-compile
url-vars cl-loaddefs cl-lib rmc iso-transl tooltip cconv eldoc paren
electric uniquify ediff-hook vc-hooks lisp-float-type elisp-mode mwheel
term/x-win x-win term/common-win x-dnd touch-screen tool-bar dnd fontset
image regexp-opt fringe tabulated-list replace newcomment text-mode
lisp-mode prog-mode register page tab-bar menu-bar rfn-eshadow isearch
easymenu timer select scroll-bar mouse jit-lock font-lock syntax
font-core term/tty-colors frame minibuffer nadvice seq simple cl-generic
indonesian philippine 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 emoji-zwj charscript charprop case-table epa-hook
jka-cmpr-hook help abbrev obarray oclosure cl-preloaded button loaddefs
theme-loaddefs faces cus-face macroexp files window text-properties
overlay sha1 md5 base64 format env code-pages mule custom widget keymap
hashtable-print-readable backquote threads inotify dynamic-setting
system-font-setting font-render-setting cairo x-toolkit x multi-tty
move-toolbar make-network-process tty-child-frames native-compile mps
emacs)

Memory information:
((conses 24 0 0) (symbols 56 0 0) (strings 40 0 0) (string-bytes 1 0)
 (vectors 24 0) (vector-slots 8 0 0) (floats 24 0 0)
 (intervals 64 0 0) (buffers 1072 0))

Message #8 received at 79014 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Óscar Fuentes <oscarfv <at> eclipso.eu>
Cc: 79014 <at> debbugs.gnu.org
Subject: Re: bug#79014: 31.0.50; igc: infinite loop
Date: Mon, 14 Jul 2025 16:16:52 +0300

> Date: Mon, 14 Jul 2025 13:15:43 +0200
> From:  Óscar Fuentes via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs <at> gnu.org>
> 
> 
> On a long-lived emacs session (two weeks of intensive use), while
> reverting a versioned file with C-x v u (something that I did multiple
> times before on the same session) Emacs entered an infinite loop using
> 100% CPU, ignoring C-g and SIGUSR2 and had to be killed eventually after
> attaching gdb and obtaining the backtraces below.
> 
> #0  truncate_undo_list (b=b <at> entry=0x7fb33b464b18) at ../../emacs/src/lisp.h:1534
>         list = <optimized out>
>         prev = <optimized out>
>         next = <optimized out>
>         last_boundary = 0x0
>         size_so_far = 20445947
>         count = {bytes = <optimized out>}
>         undo_outer_limit = <optimized out>
> #1  0x00005596d35701d9 in compact_buffer (buffer=buffer <at> entry=0x7fb33b464b18)
>     at ../../emacs/src/buffer.c:1874
> #2  0x00005596d36669e2 in buffer_step (it=<synthetic pointer>) at ../../emacs/src/igc.c:4051
>         buf = 0x7fb33b464b1d
>         b = 0x7fb33b464b18
> #3  igc_on_idle () at ../../emacs/src/igc.c:4083
>         work_done = <optimized out>
>         clock = {expire = <optimized out>}
>         buffer_it = {alist = <optimized out>, buf = <optimized out>}
> #4  0x00005596d354f2b5 in timer_check_2 (timers=<optimized out>, idle_timers=<optimized out>)
>     at ../../emacs/src/keyboard.c:4722
>         now = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
>         idleness_now = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
>         now = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
>         idleness_now = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
>         funcall = <optimized out>
>         chosen_timer = <optimized out>
>         timer = <optimized out>
>         idle_timer = <optimized out>
> --Type <RET> for more, q to quit, c to continue without paging--
>         difference = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
>         timer_difference = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
>         idle_timer_difference = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
>         ripe = <optimized out>
>         timer_ripe = <optimized out>
>         idle_timer_ripe = <optimized out>
>         timer_time = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
>         idle_timer_time = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
>         count = {bytes = <optimized out>}
>         old_deactivate_mark = <optimized out>
> #5  timer_check () at ../../emacs/src/keyboard.c:4891
>         nexttime = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
>         timers = 0x7fb256c7dc73
>         idle_timers = <optimized out>
>         tem = <optimized out>
> #6  0x00005596d354f7e5 in readable_events (flags=flags <at> entry=3) at ../../emacs/src/keyboard.c:3618
> #7  0x00005596d354f9c0 in get_input_pending (flags=flags <at> entry=3) at ../../emacs/src/keyboard.c:8007
> #8  0x00005596d354fad5 in Finput_pending_p (check_timers=0x38) at ../../emacs/src/keyboard.c:11799
> #9  0x00007fb32f4ed5b2 in F7369742d666f72_sit_for_0 ()
>     at /home/oscar/dev/emacs/igc/build/src/../native-lisp/31.0.50-61e73da1/preloaded/subr-13adf6a6-dbedbcf7.eln
> #10 0x00005596d35d6a0c in Ffuncall (nargs=2, args=0x7fff3751ec00) at ../../emacs/src/eval.c:3195
>         count = {bytes = <optimized out>}
>         val = <optimized out>
> #11 0x00007fb32e40648e in F646973706c61792d7761726e696e67_display_warning_0 ()
>     at /home/oscar/.emacs.d/eln-cache/31.0.50-61e73da1/warnings-28e75f4d-f0ade81c.eln
> #12 0x00005596d35d6a0c in Ffuncall (nargs=4, args=0x7fff3751ee00) at ../../emacs/src/eval.c:3195
> --Type <RET> for more, q to quit, c to continue without paging--
>         count = {bytes = <optimized out>}
>         val = <optimized out>
> #13 0x00007fb32f243db7 in F756e646f2d6f757465722d6c696d69742d7472756e63617465_undo_outer_limit_truncate_0
>     ()
>     at /home/oscar/dev/emacs/igc/build/src/../native-lisp/31.0.50-61e73da1/preloaded/simple-fab5b0cf-9e866eaa.eln
> #14 0x00005596d35d6a0c in Ffuncall (nargs=nargs <at> entry=2, args=args <at> entry=0x7fff3751ee80)
>     at ../../emacs/src/eval.c:3195
>         count = {bytes = <optimized out>}
>         val = <optimized out>
> #15 0x00005596d35ae9ed in truncate_undo_list (b=b <at> entry=0x7fb33b464b18) at ../../emacs/src/undo.c:366
>         tem = <optimized out>
>         list = <optimized out>
>         prev = <optimized out>
>         next = <optimized out>
>         last_boundary = 0x0
>         size_so_far = <optimized out>
>         count = {bytes = <optimized out>}
>         undo_outer_limit = <optimized out>
> #16 0x00005596d35701d9 in compact_buffer (buffer=buffer <at> entry=0x7fb33b464b18)
>     at ../../emacs/src/buffer.c:1874
> #17 0x00005596d36669e2 in buffer_step (it=<synthetic pointer>) at ../../emacs/src/igc.c:4051
>         buf = 0x7fb33b464b1d
>         b = 0x7fb33b464b18
> #18 igc_on_idle () at ../../emacs/src/igc.c:4083
>         work_done = <optimized out>
>         clock = {expire = <optimized out>}
> --Type <RET> for more, q to quit, c to continue without paging--
>         buffer_it = {alist = <optimized out>, buf = <optimized out>}
> #19 0x00005596d354f2b5 in timer_check_2 (timers=<optimized out>, idle_timers=<optimized out>)
>     at ../../emacs/src/keyboard.c:4722
>         now = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
>         idleness_now = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
>         now = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
>         idleness_now = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
>         funcall = <optimized out>
>         chosen_timer = <optimized out>
>         timer = <optimized out>
>         idle_timer = <optimized out>
>         difference = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
>         timer_difference = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
>         idle_timer_difference = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
>         ripe = <optimized out>
>         timer_ripe = <optimized out>
>         idle_timer_ripe = <optimized out>
>         timer_time = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
>         idle_timer_time = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
>         count = {bytes = <optimized out>}
>         old_deactivate_mark = <optimized out>
> #20 timer_check () at ../../emacs/src/keyboard.c:4891
>         nexttime = {tv_sec = <optimized out>, tv_nsec = <optimized out>}
>         timers = 0x7fb256c795b3
>         idle_timers = <optimized out>
>         tem = <optimized out>
> 
> 
> 
> (gdb) xbacktrace
> "sit-for" (0x3751ec08)
> "display-warning" (0x3751ee08)
> "undo-outer-limit-truncate" (0x3751ee88)
> "sit-for" (0x3751f1c8)
> "display-warning" (0x3751f3c8)
> "undo-outer-limit-truncate" (0x3751f448)
> "sit-for" (0x3751f788)
> "display-warning" (0x3751f988)
> "undo-outer-limit-truncate" (0x3751fa08)
> "sit-for" (0x3751fd48)
> "display-warning" (0x3751ff48)
> "undo-outer-limit-truncate" (0x3751ffc8)
> "sit-for" (0x37520308)
> "display-warning" (0x37520508)
> "undo-outer-limit-truncate" (0x37520588)
> "sit-for" (0x375208c8)
> "display-warning" (0x37520ac8)
> "undo-outer-limit-truncate" (0x37520b48)
> "sit-for" (0x37520e88)
> "display-warning" (0x37521088)
> "undo-outer-limit-truncate" (0x37521108)
> "sit-for" (0x37521448)
> "display-warning" (0x37521648)
> "undo-outer-limit-truncate" (0x375216c8)
> "sit-for" (0x37521a08)
> "display-warning" (0x37521c08)
> "undo-outer-limit-truncate" (0x37521c88)

Any idea what it was trying to warn about in display-warning frames?
I suspect it's some kind of memory-full situation.

Do you still have that session in GDB?

Message #11 received at 79014 <at> debbugs.gnu.org (full text, mbox):

From: Óscar Fuentes <oscarfv <at> eclipso.eu>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 79014 <at> debbugs.gnu.org
Subject: Re: bug#79014: 31.0.50; igc: infinite loop
Date: Mon, 14 Jul 2025 15:35:17 +0200

Eli Zaretskii <eliz <at> gnu.org> writes:

> Any idea what it was trying to warn about in display-warning frames?

No, sorry.

> I suspect it's some kind of memory-full situation.

I'll mention this in case it is relevant: Emacs was using about 2.8 GB
of RSS and that machine has 64 GB of RAM, almost all free.

> Do you still have that session in GDB?

No :-(

Message #14 received at 79014 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Óscar Fuentes <oscarfv <at> eclipso.eu>
Cc: 79014 <at> debbugs.gnu.org
Subject: Re: bug#79014: 31.0.50; igc: infinite loop
Date: Mon, 14 Jul 2025 16:45:38 +0300

> From: Óscar Fuentes <oscarfv <at> eclipso.eu>
> Cc: 79014 <at> debbugs.gnu.org
> Date: Mon, 14 Jul 2025 15:35:17 +0200
> 
> Eli Zaretskii <eliz <at> gnu.org> writes:
> 
> > Any idea what it was trying to warn about in display-warning frames?
> 
> No, sorry.
> 
> > I suspect it's some kind of memory-full situation.
> 
> I'll mention this in case it is relevant: Emacs was using about 2.8 GB
> of RSS and that machine has 64 GB of RAM, almost all free.
> 
> > Do you still have that session in GDB?
> 
> No :-(

Then I don't see how we could do anything with this report.  Too bad.
Please in the future try to leave the crashed session inside GDB at
least for a while.

Unless someone has ideas how to make some progress with this bug, I
will soon close it as unreproducible.

Message #17 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Gerd Möllmann <gerd.moellmann <at> gmail.com>
To: Óscar Fuentes via "Bug reports for GNU Emacs, the Swiss
 army knife of text editors" <bug-gnu-emacs <at> gnu.org>
Cc: Óscar Fuentes <oscarfv <at> eclipso.eu>, 79014 <at> debbugs.gnu.org
Subject: Re: bug#79014: 31.0.50; igc: infinite loop
Date: Mon, 14 Jul 2025 15:50:58 +0200

[Message part 1 (text/plain, inline)]

Óscar Fuentes via "Bug reports for GNU Emacs, the Swiss army knife of
text editors" <bug-gnu-emacs <at> gnu.org> writes:

> On a long-lived emacs session (two weeks of intensive use), while
> reverting a versioned file with C-x v u (something that I did multiple
> times before on the same session) Emacs entered an infinite loop using
> 100% CPU, ignoring C-g and SIGUSR2 and had to be killed eventually after
> attaching gdb and obtaining the backtraces below.

Thanks. That's a recursive call to igc_on_idle from Lisp being called
whle it is running. Looks like something like this is needed:

[on_idle.diff (text/x-patch, attachment)]

Message #23 received at 79014 <at> debbugs.gnu.org (full text, mbox):

From: Óscar Fuentes <oscarfv <at> eclipso.eu>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: pipcet <at> protonmail.com, 79014 <at> debbugs.gnu.org
Subject: Re: bug#79014: 31.0.50; igc: infinite loop
Date: Mon, 14 Jul 2025 16:27:25 +0200

Eli Zaretskii <eliz <at> gnu.org> writes:

>> > Any idea what it was trying to warn about in display-warning frames?
>> 
>> No, sorry.
>> 
>> > I suspect it's some kind of memory-full situation.
>> 
>> I'll mention this in case it is relevant: Emacs was using about 2.8 GB
>> of RSS and that machine has 64 GB of RAM, almost all free.
>> 
>> > Do you still have that session in GDB?
>> 
>> No :-(
>
> Then I don't see how we could do anything with this report.  Too bad.
> Please in the future try to leave the crashed session inside GDB at
> least for a while.

That's a remote machine that runs Emacs as a daemon. Probably I could
figure out how to run another remote instance without killing the
previous one, but I had urgent work to do.

> Unless someone has ideas how to make some progress with this bug, I
> will soon close it as unreproducible.

Let's see what Pip has to say.

I think I have seen a similar backtrace on the past. The sequence of
nested calls doesn't look too sane (timer_check ... igc_on_idle ...
truncate_undo_list ... display_warning ... Finput_pending_p ...
timer_check) but as mini-echo-mode [1] was active, it starts making
sense.

mini-echo hides the modeline and uses a repeating idle timer for
updating the echo area with the information that usually would be in the
modeline. That can execute arbitrary code.

Bug 74547 was also a crash with the igc/mini-echo combo. Looks like if
the mini-echo timer does its thing at the "wrong" moment wrt igc state,
problems arise.

For starters, does it make sense for igc_on_idle to be recursive?
Can't that function detect that is being called recursively and just
return?

Another thought: does the time consumed by igc_on_idle count as idle
time for idle timers?

1 https://github.com/eki3z/mini-echo.el

Message #26 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Óscar Fuentes <oscarfv <at> eclipso.eu>
To: Gerd Möllmann <gerd.moellmann <at> gmail.com>
Cc: "Óscar Fuentes via Bug reports for GNU Emacs, the Swiss
 army knife of text editors" <bug-gnu-emacs <at> gnu.org>, 79014 <at> debbugs.gnu.org
Subject: Re: bug#79014: 31.0.50; igc: infinite loop
Date: Mon, 14 Jul 2025 16:37:12 +0200

Gerd Möllmann <gerd.moellmann <at> gmail.com> writes:

> Thanks. That's a recursive call to igc_on_idle from Lisp being called
> whle it is running. Looks like something like this is needed:

Thanks Gerd. Looks like the backtrace was useful after all :-)

As I implied on my previous message, it would be useful to understand in
what circunstances a recursive call to igc_on_idle happens. More
precisely, why Emacs enters an idle state within an idle state. And how
the time used by igc_on_idle is accounted for idle timers.

Those are general questions, not addressed at you specifically.

Message #32 received at 79014 <at> debbugs.gnu.org (full text, mbox):

From: Gerd Möllmann <gerd.moellmann <at> gmail.com>
To: Óscar Fuentes <oscarfv <at> eclipso.eu>
Cc: "Óscar Fuentes via Bug reports for GNU Emacs, the Swiss
 army knife of text editors" <bug-gnu-emacs <at> gnu.org>, 79014 <at> debbugs.gnu.org
Subject: Re: bug#79014: 31.0.50; igc: infinite loop
Date: Mon, 14 Jul 2025 17:03:49 +0200

Óscar Fuentes <oscarfv <at> eclipso.eu> writes:

> Gerd Möllmann <gerd.moellmann <at> gmail.com> writes:
>
>> Thanks. That's a recursive call to igc_on_idle from Lisp being called
>> whle it is running. Looks like something like this is needed:
>
> Thanks Gerd. Looks like the backtrace was useful after all :-)

:-)

>
> As I implied on my previous message, it would be useful to understand in
> what circunstances a recursive call to igc_on_idle happens. More
> precisely, why Emacs enters an idle state within an idle state. And how
> the time used by igc_on_idle is accounted for idle timers.
>
> Those are general questions, not addressed at you specifically.

It's difficult.

igc_on_indle is called when timer_check runs. That function basically
let's Lisp timers work as one would expect, and that is done, because
everything is synchronous, by calling timer_check at points where
someone though we have the time to do it.

One point is when reading input events and another is somewhere in
wait_reading_process_input. And it happens that in your case somewhere
in the Ffuncall that was on the backtrace one of the points was hit.

IOW, in this case, timer_check was also called recursively. But since
that can apparently happen independent of igc, I've left it alone of
course.

Maybe also igc_on_idle is not a good name. Don't know.

My 2 cents. Maybe someone else can say more, or has an idea how to do it
better. 

Message #38 received at 79014 <at> debbugs.gnu.org (full text, mbox):

From: Pip Cet <pipcet <at> protonmail.com>
To: Óscar Fuentes <oscarfv <at> eclipso.eu>
Cc: Eli Zaretskii <eliz <at> gnu.org>, 79014 <at> debbugs.gnu.org
Subject: Re: bug#79014: 31.0.50; igc: infinite loop
Date: Mon, 14 Jul 2025 15:08:23 +0000

Óscar Fuentes <oscarfv <at> eclipso.eu> writes:

> Eli Zaretskii <eliz <at> gnu.org> writes:
>
>>> > Any idea what it was trying to warn about in display-warning frames?
>>>
>>> No, sorry.
>>>
>>> > I suspect it's some kind of memory-full situation.
>>>
>>> I'll mention this in case it is relevant: Emacs was using about 2.8 GB
>>> of RSS and that machine has 64 GB of RAM, almost all free.
>>>
>>> > Do you still have that session in GDB?
>>>
>>> No :-(
>>
>> Then I don't see how we could do anything with this report.  Too bad.
>> Please in the future try to leave the crashed session inside GDB at
>> least for a while.
>
> That's a remote machine that runs Emacs as a daemon. Probably I could
> figure out how to run another remote instance without killing the
> previous one, but I had urgent work to do.

>> Unless someone has ideas how to make some progress with this bug, I
>> will soon close it as unreproducible.
>
> Let's see what Pip has to say.

I'll have to look up the conversation, but IIRC, this is a clear bug:
igc_on_idle shouldn't always start on the same buffer, and it should not
call itself recursively; compact_buffer should not attempt to truncate
an undo list in a recursive call, either.  I'm pretty sure I suggested
moving this line

      BUF_COMPACT (buffer) = BUF_MODIFF (buffer);

in compact_buffer to happen before we call truncate_undo_list, which
would prevent this infloop, but there's more than one thing to be fixed
here.

> For starters, does it make sense for igc_on_idle to be recursive?

No, I don't think it does. If I'm reading the code correctly,
display-warning calls (sit-for 0), and that probably shouldn't cause us
to become idle at all.

> Can't that function detect that is being called recursively and just
> return?

I'm not sure I have a good idea of how to fix this yet. igc_on_idle
appears to be called in the wrong place if there's a possibility it
calls out to Lisp, too.

> Another thought: does the time consumed by igc_on_idle count as idle
> time for idle timers?

I'd like to rephrase that a little: why isn't igc_on_idle an idle timer?
There's already some logic in keyboard.c to run idle timers at the
correct time, when actually idle, so we could reuse that for the idle
work that igc.c needs to do.

For now, though, let's do this (on feature/igc):

From 41d3fdf4c394c14e3beed1eda3caec6b8e57cb2f Mon Sep 17 00:00:00 2001
From: Pip Cet <pipcet <at> protonmail.com>
Date: Mon, 14 Jul 2025 15:05:05 +0000
Subject: [PATCH] Avoid infloops during buffer compaction (bug#79014)

* src/buffer.c (compact_buffer): Set the 'BUF_COMPACT' timestamp
before entering truncate_undo_list; that way, if truncate_undo_list
calls this function recursively, the same buffer will not be
considered for compaction twice.
---
 src/buffer.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/buffer.c b/src/buffer.c
index b85394cff3b..e474b8f9dfe 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -1866,6 +1866,10 @@ compact_buffer (struct buffer *buffer)
       && (buffer->base_buffer == NULL)
       && (BUF_COMPACT (buffer) != BUF_MODIFF (buffer)))
     {
+      /* This needs to be first: truncate_undo_list can call out to
+	 Lisp, which may result in this function being reentered.  Make
+	 sure we don't infloop in this case.  */
+      BUF_COMPACT (buffer) = BUF_MODIFF (buffer);
       /* If a buffer's undo list is Qt, that means that undo is
 	 turned off in that buffer.  Calling truncate_undo_list on
 	 Qt tends to return NULL, which effectively turns undo back on.
@@ -1885,7 +1889,6 @@ compact_buffer (struct buffer *buffer)
 	  if (BUF_GAP_SIZE (buffer) > size)
 	    make_gap_1 (buffer, -(BUF_GAP_SIZE (buffer) - size));
 	}
-      BUF_COMPACT (buffer) = BUF_MODIFF (buffer);
     }
 }
 
-- 
2.50.0

Message #41 received at 79014 <at> debbugs.gnu.org (full text, mbox):

From: Óscar Fuentes <oscarfv <at> eclipso.eu>
To: Pip Cet <pipcet <at> protonmail.com>
Cc: Eli Zaretskii <eliz <at> gnu.org>, 79014 <at> debbugs.gnu.org
Subject: Re: bug#79014: 31.0.50; igc: infinite loop
Date: Tue, 15 Jul 2025 11:54:06 +0200

Hello Pip. Was the patch below posted for discussion or did you forgot
to push it to feature/igc?

I'll like to rebuild Emacs with the fix and having it on the branch is
much preferable to applying it as a patch.

And while we are at it, I hope there are no objections if I merge master
into feature/igc.

Thanks.

Pip Cet <pipcet <at> protonmail.com> writes:

> For now, though, let's do this (on feature/igc):
>
> From 41d3fdf4c394c14e3beed1eda3caec6b8e57cb2f Mon Sep 17 00:00:00 2001
> From: Pip Cet <pipcet <at> protonmail.com>
> Date: Mon, 14 Jul 2025 15:05:05 +0000
> Subject: [PATCH] Avoid infloops during buffer compaction (bug#79014)
>
> * src/buffer.c (compact_buffer): Set the 'BUF_COMPACT' timestamp
> before entering truncate_undo_list; that way, if truncate_undo_list
> calls this function recursively, the same buffer will not be
> considered for compaction twice.

Message #44 received at 79014 <at> debbugs.gnu.org (full text, mbox):

From: Óscar Fuentes <oscarfv <at> eclipso.eu>
To: Pip Cet <pipcet <at> protonmail.com>, Gerd Möllmann
 <gerd.moellmann <at> gmail.com>
Cc: Eli Zaretskii <eliz <at> gnu.org>, 79014 <at> debbugs.gnu.org
Subject: Re: bug#79014: 31.0.50; igc: infinite loop
Date: Wed, 16 Jul 2025 15:54:44 +0200

Gerd, Pip:

Which patch should I apply? Both, perhaps?

Message #47 received at 79014 <at> debbugs.gnu.org (full text, mbox):

From: Pip Cet <pipcet <at> protonmail.com>
To: Óscar Fuentes <oscarfv <at> eclipso.eu>
Cc: Gerd Möllmann <gerd.moellmann <at> gmail.com>,
 Eli Zaretskii <eliz <at> gnu.org>, 79014 <at> debbugs.gnu.org
Subject: Re: bug#79014: 31.0.50; igc: infinite loop
Date: Wed, 16 Jul 2025 13:57:07 +0000

Óscar Fuentes <oscarfv <at> eclipso.eu> writes:

> Gerd, Pip:
>
> Which patch should I apply? Both, perhaps?

Try Gerd's patch first, I'd suggest; it changes less than mine does, and
it should be sufficient to avoid the problem.

Pip

Message #50 received at 79014 <at> debbugs.gnu.org (full text, mbox):

From: Gerd Möllmann <gerd.moellmann <at> gmail.com>
To: Pip Cet <pipcet <at> protonmail.com>
Cc: Óscar Fuentes <oscarfv <at> eclipso.eu>,
 Eli Zaretskii <eliz <at> gnu.org>, 79014 <at> debbugs.gnu.org
Subject: Re: bug#79014: 31.0.50; igc: infinite loop
Date: Wed, 16 Jul 2025 16:34:40 +0200

Pip Cet <pipcet <at> protonmail.com> writes:

> Óscar Fuentes <oscarfv <at> eclipso.eu> writes:
>
>> Gerd, Pip:
>>
>> Which patch should I apply? Both, perhaps?
>
> Try Gerd's patch first, I'd suggest; it changes less than mine does, and
> it should be sufficient to avoid the problem.
>
> Pip

I'm about to push what I have in my Emacs, when it builds successfully.

(Sorry, I didn't see your patch. I guess I'm a bit out of the loop, meanhilw.)

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