--- Begin Message ---
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Subject: |
24.3; interaction with external process hangs emacs |
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Date: |
Sun, 07 Sep 2014 03:04:51 -0500 |
While developing an external parser for Emacs Ada Mode 5.x, I ran into a
situation where Emacs is hung while sending to and receiving from the
external parser; C-g does not recover. Separately killing the external
process does recover.
The bug with the full Emacs Ada mode and full external parser is quite
repeatable; it happens every time the
`wisi-ada-parse-session-send-parse' command is invoked on a sufficiently
large buffer, but only with the full development sources. I tried to
produce a simplified elisp and external code, but those do not reproduce
the bug.
The elisp that hangs is:
(defun wisi-ada-parse-session-send-parse ()
"Send a parse command to ada_mode_wisi_parse session, followed by the
contents of the current buffer."
(wisi-ada-parse-require-session)
;; ada_mode_wisi_parse can't handle non-ASCII, so we don't need string-bytes
here.
(let* ((buf-string (buffer-substring-no-properties (point-min) (point-max)))
(byte-count-img (format "%d" (1- (length buf-string))))
(cmd (concat "parse " byte-count-img))
(msg (format "%02d%s" (length cmd) cmd))
(process (wisi-ada-parse--session-process wisi-ada-parse-session)))
(when (> wisi-ada-parse-debug 0)
(wisi-ada-parse-show-buffer)
(message msg))
(with-current-buffer (wisi-ada-parse--session-buffer wisi-ada-parse-session)
(erase-buffer))
(process-send-string process msg)
;; WORKAROUND: process-send-string is supposed to allow accepting
;; process output while writing to process input, but apparently
;; it doesn't, at least on windows via pipes. So break up
;; buf-string, and call accept-process-output explicitly
(let ((bytes-per-cycle 2047)
(bytes-to-send (length buf-string))
(first 0)
(last 0))
(while (< last bytes-to-send)
(setq last (min bytes-to-send (+ first bytes-per-cycle)))
(message "%d" last)
(process-send-string process (substring buf-string first last))
(setq first (1+ last))
(accept-process-output process 0.1)))
(wisi-ada-parse-session-wait)
))
It hangs on one of the process-send-string calls in the WORKAROUND loop.
The loop is replacing an earlier version that used a single
process-send-string to send the entire buffer string. I was hoping that
the explicit accept-process-out calls would allow C-g to work, but
apparently not.
The external process implements an LALR parser for Ada source; it
outputs the parse results back to Emacs. There is a lot of output, so
it can easily fill up the IO queue. Attaching to that process when
Emacs is hung shows it is blocked writing to stdout, in a normal part
of the code flow.
Attaching the debugger I have to the Emacs process shows that it is
also blocked in WriteFile, called from emacs_write, but I can't see
any farther up the stack; the debugger says the stack is corrupt. I
don't have debugging symbols, so I can't tell where in Emacs write it
is.
I'm working on building Emacs from the pre-release source, and
installing a compatible debugger.
In GNU Emacs 24.3.1 (i386-mingw-nt6.1.7601)
of 2013-03-17 on MARVIN
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
`configure --with-gcc (4.7) --cflags
-ID:/devel/emacs/libs/libXpm-3.5.8/include
-ID:/devel/emacs/libs/libXpm-3.5.8/src
-ID:/devel/emacs/libs/libpng-dev_1.4.3-1/include
-ID:/devel/emacs/libs/zlib-dev_1.2.5-2/include
-ID:/devel/emacs/libs/giflib-4.1.4-1/include
-ID:/devel/emacs/libs/jpeg-6b-4/include
-ID:/devel/emacs/libs/tiff-3.8.2-1/include
-ID:/devel/emacs/libs/gnutls-3.0.9/include
-ID:/devel/emacs/libs/libiconv-1.13.1-1-dev/include
-ID:/devel/emacs/libs/libxml2-2.7.8/include/libxml2'
Important settings:
value of $LANG: en_US.UTF-8
locale-coding-system: cp1252
default enable-multibyte-characters: t
Major mode: Ada
Minor modes in effect:
shell-dirtrack-mode: t
diff-auto-refine-mode: t
display-time-mode: t
delete-selection-mode: t
tooltip-mode: t
mouse-wheel-mode: t
menu-bar-mode: t
file-name-shadow-mode: t
global-font-lock-mode: t
font-lock-mode: t
auto-composition-mode: t
auto-encryption-mode: t
auto-compression-mode: t
column-number-mode: t
line-number-mode: t
transient-mark-mode: t
Recent input:
<up> <up> <up> <up> <up> <up> <up> <up> <up> <up> <up>
<up> <up> <up> <up> <up> <up> <up> <up> <up> <up> <up>
<up> <up> <up> <up> <up> <up> <up> <up> <up> <up> <up>
<up> <up> <up> <up> <up> <up> <up> <up> <up> <up> <up>
<up> <up> <up> <up> <up> <up> <up> <up> <up> <up> <up>
<C-M-up> <f11> . a d s <backspace> d b <backspace>
<backspace> b <return> <up> <up> <M-right> <M-right>
<M-right> <S-left> 2 <S-left> 3 <f5> <C-M-down> <f5>
<up> <return> <C-M-up> <M-home> <down> <down> <down>
<down> <down> <down> <down> <down> <down> <down> <down>
<down> <down> <down> <down> <down> <down> <down> <down>
<down> <down> <down> <down> <down> <down> <down> <down>
<down> <M-right> <M-right> <M-right> <M-right> <M-right>
<M-right> <S-left> 3 <M-down> <M-down> <M-down> <M-down>
<M-down> <M-down> <down> <down> <down> <down> <down>
<down> <down> <down> <down> <down> <return> <home>
C-SPC <down> <down> <down> <down> <down> <M-delete>
<insert> <up> <up> <up> <up> <up> <up> <up> <up> <up>
<M-right> <M-right> <M-right> <S-left> 1 <end> <return>
- - SPC SPC <up> <M-right> <M-right> <S-left> - <backspace>
0 <down> E m a c s SPC d o e s n ' t SPC h a v e SPC
a SPC c h a n g <backspace> c e SPC t o SPC r e a d
SPC t h e SPC t e x t SPC w e SPC j u s t SPC o u t
p u t SPC b e f o r e SPC e <backspace> w e SPC d i
e . <f4> M-w <f5> y e s <return> <lwindow> <switch-frame>
<switch-frame> <f6> <down> <down> <down> <down> <down>
<down> <down> <down> <down> <down> <down> <M-right>
<right> <S-right> 3 <f6> <f6> <down> <down> <down>
<down> <M-right> <right> <right> SPC | SPC 3 <f5> M-x
r e p o r <tab> <return>
Recent messages:
(No files need saving)
Mark set [3 times]
Saving file
c:/home/stephe/Emacs_Work/background_proc_hangs_emacs/ada_mode_wisi_parse.adb...
Wrote
c:/home/stephe/Emacs_Work/background_proc_hangs_emacs/ada_mode_wisi_parse.adb
(No files need saving)
Compilation killed
Compilation exited abnormally with code 2
Saving file
c:/home/stephe/Emacs_Work/background_proc_hangs_emacs/ada_mode_wisi_parse.adb...
Wrote
c:/home/stephe/Emacs_Work/background_proc_hangs_emacs/ada_mode_wisi_parse.adb
Compilation finished
Load-path shadows:
/Projects/org.emacs.ada-mode.stephe-1/ada-mode hides
c:/Apps/emacs-24.3/lisp/progmodes/ada-mode
Features:
(shadow mail-extr emacsbug message format-spec rfc822 mml mml-sec
mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils
mailheader sendmail rfc2047 rfc2045 ietf-drums mail-utils
dvc-persistence dvc-config dvc-propagate dvc-state debug edebug bzr-dvc
bzr dvc-annotate dvc-revlist etags else-mode cc-langs cc-mode cc-fonts
cc-guess cc-menus cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs
find-func help-mode hippie-exp gud sort rect wisi-parse copyright tabify
misearch multi-isearch shell pcomplete gpr-query make-mode xmtn-dvc
dvc-status dvc-diff dvc-fileinfo diff-mode xmtn-conflicts xmtn-ids
xmtn-match xmtn-automate xmtn-compat parse-time xmtn-run xmtn-basic-io
xmtn-base ada-skel ada-skeletons skeleton ada-compiler ada-gnat-compile
ada-xref-tool ada-gnat-xref gnat-core wisi-ada-parse ada-indent-engine
ada-wisi ada-indent-user-options ada_grammar-wy wisi-compile
semantic/wisent/comp semantic/wisent semantic/wisent/wisent
semantic/util-modes semantic/util semantic semantic/tag cedet
semantic/lex semantic/fw mode-local wisi wisi-compat-24.2
wisi-parse-common ada-fix-error ada-build ada-mode find-file align
xgit-core bzr-core xmtn-minimal dvc-log log-edit pcvs-util vc
vc-dispatcher ediff-merg ediff-diff ediff-wind ediff-help ediff-util
ediff-mult ediff-init ediff dvc-unified dvc-tips ffap url-parse
auth-source eieio byte-opt bytecomp byte-compile cconv gnus-util mm-util
mail-prsvr password-cache url-vars add-log dvc-autoloads dvc-core
dvc-lisp dvc-buffers dvc-ui dvc-register dvc-utils dvc-emacs ewoc
dvc-defs dvc-site uniquify advice help-fns advice-preload time delsel
cus-start cus-load color-theme cl-macs gv edmacro kmacro wid-edit cl
cl-lib noutline outline easy-mmode iswitchb whitespace dired-x dired-aux
dired compile comint ansi-color ring bbdb-autoloads info easymenu
package time-date tooltip ediff-hook vc-hooks lisp-float-type mwheel
dos-w32 ls-lisp w32-common-fns disp-table w32-win w32-vars tool-bar dnd
fontset image regexp-opt fringe tabulated-list newcomment lisp-mode
register page menu-bar rfn-eshadow timer select scroll-bar mouse
jit-lock font-lock syntax facemenu font-core frame cham georgian
utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean
japanese hebrew greek romanian slovak czech european ethiopic indian
cyrillic chinese case-table epa-hook jka-cmpr-hook help simple abbrev
minibuffer loaddefs button faces cus-face macroexp files text-properties
overlay sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote make-network-process w32 multi-tty
emacs)
--- End Message ---
--- Begin Message ---
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Subject: |
Re: bug#18420: 24.3; interaction with external process hangs emacs |
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Date: |
Sun, 14 Sep 2014 18:20:02 +0300 |
> From: Stephen Leake <address@hidden>
> Cc: address@hidden
> Date: Tue, 09 Sep 2014 16:48:26 -0500
>
> Eli Zaretskii <address@hidden> writes:
>
> > Anyway, it turns out we can make our pipes non-blocking on write,
> > which then allows us to use the EWOULDBLOCK/EAGAIN handling in
> > send_process. Please try the patch below, and if it gives good
> > results, I will install it shortly.
>
> Yes, it fixes the problem.
Thanks, I installed this on the emacs-24 branch.
--- End Message ---