Bug#1014873: tigervnc-scraping-server: X0tigervnc server died with signal 6! / Assertion `!xcb_xlib_threads_sequence_lost' failed.
Package: libx11-6
Version: 2:1.7.5-1
Severity: normal
X-Debbugs-Cc: bernhardu@mailbox.org
Dear Maintainer,
I observe following aborts [1] of a X0tigervnc attaching to a running
X-server showing a KDE/Plasma session at a Bookworm/testing system.
To this VNC server I connect with xtigervncviewer from Bullseye/stable.
In the logfile appears the assertion [2], at the backtrace [3].
Previous visits in this function normally have
variable req containing a proper pointer, but at the failing
visit it contains NULL.
There exists a tigervnc upstream bug [4], where it is believed
this might be an issue in libx11-6 or libxcb1.
It somehow might be related to a libx11-6 upstream merge request [5],
which did fix a similar "xcb_xlib_threads_sequence_lost" issue for
the remote-viewer application.
Unfortunately I miss the knowledge how this parts should operate.
I can reproduce it quite reliable, also while recording with rr-debugger.
Any hints how to debug this further, where it starts to go wrong?
Kind regards,
Bernhard
[1]
$ DISPLAY=:0 x0tigervncserver -rfbport 5910 -fg -verbose
Starting /usr/bin/X0tigervnc -localhost=1 -desktop rechner:0 (bernhard) -rfbport 5910 -PasswordFile /home/bernhard/.vnc/passwd -SecurityTypes VncAuth
New X0tigervnc server 'rechner:0 (bernhard)' on port 5910 for display :0.
Use xtigervncviewer -SecurityTypes VncAuth -passwd /home/bernhard/.vnc/passwd :10 to connect to the VNC server.
The X0tigervnc server died with signal 6!
$
[2]
$ cat .vnc/rechner\:5910.log
...
[xcb] Unknown sequence number while processing queue
[xcb] Most likely this is a multi-threaded client and XInitThreads has not been called
[xcb] Aborting, sorry about that.
X0tigervnc: ../../src/xcb_io.c:278: poll_for_event: Assertion `!xcb_xlib_threads_sequence_lost' failed.
$
[3]
(rr) reverse-finish
Run back to call of #0 0x00007f8a5365821d in __GI___assert_fail (assertion=assertion@entry=0x7f8a53ce1aa0 "!xcb_xlib_threads_sequence_lost", file=file@entry=0x7f8a53ce18d3 "../../src/xcb_io.c", line=line@entry=278, function=function@entry=0x7f8a53ce1d68 <__PRETTY_FUNCTION__.7> "poll_for_event") at assert.c:101
0x00007f8a53c6ca2f in poll_for_event (dpy=dpy@entry=0x555d222ac400, queued_only=0) at ../../src/xcb_io.c:278
278 throw_thread_fail_assert("Unknown sequence "
1: /x event_sequence = 0xfff6
2: /x request = 0x557a
3: req = (PendingRequest *) 0x0
(rr) bt
#0 0x00007f8a53c6ca2f in poll_for_event (dpy=dpy@entry=0x555d222ac400, queued_only=0) at ../../src/xcb_io.c:278
#1 0x00007f8a53c6cae8 in poll_for_response (dpy=dpy@entry=0x555d222ac400) at ../../src/xcb_io.c:310
#2 0x00007f8a53c6ceb2 in _XEventsQueued (mode=2, dpy=0x555d222ac400) at ../../src/xcb_io.c:441
#3 _XEventsQueued (dpy=dpy@entry=0x555d222ac400, mode=mode@entry=2) at ../../src/xcb_io.c:423
#4 0x00007f8a53c5e641 in XPending (dpy=0x555d222ac400) at ../../src/Pending.c:55
#5 0x0000555d21b515a8 in TXWindow::handleXEvents (dpy=dpy@entry=0x555d222ac400) at ./unix/tx/TXWindow.cxx:104
#6 0x0000555d21b44e48 in main (argc=<optimized out>, argv=<optimized out>) at ./unix/x0vncserver/x0vncserver.cxx:337
(rr) list 272,282
272 if(!req || XLIB_SEQUENCE_COMPARE(event_sequence, <, req->sequence)
273 || (event->response_type != X_Error && event_sequence == req->sequence))
274 {
275 uint64_t request = X_DPY_GET_REQUEST(dpy);
276 if (XLIB_SEQUENCE_COMPARE(event_sequence, >, request))
277 {
278 throw_thread_fail_assert("Unknown sequence "
279 "number while "
280 "processing queue",
281 xcb_xlib_threads_sequence_lost);
282 }
(rr) info thread
Id Target Id Frame
* 1 Thread 275172.275172 (X0tigervnc) 0x00007f8a53c6ca2f in poll_for_event (dpy=dpy@entry=0x555d222ac400, queued_only=0) at ../../src/xcb_io.c:278
[4]
https://github.com/TigerVNC/tigervnc/issues/869
[5]
https://gitlab.freedesktop.org/xorg/lib/libx11/-/merge_requests/53
https://bugzilla.redhat.com/show_bug.cgi?id=1758384
-- System Information:
Debian Release: bookworm/sid
APT prefers testing-proposed-updates-debug
APT policy: (500, 'testing-proposed-updates-debug'), (500, 'testing-proposed-updates'), (500, 'testing-debug'), (500, 'testing')
Architecture: amd64 (x86_64)
Foreign Architectures: i386
Kernel: Linux 5.18.0-2-amd64 (SMP w/16 CPU threads; PREEMPT)
Kernel taint flags: TAINT_WARN, TAINT_OOT_MODULE, TAINT_UNSIGNED_MODULE
Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
Versions of packages tigervnc-scraping-server depends on:
ii libc6 2.33-7
ii libfile-readbackwards-perl 1.06-1
ii libgcc-s1 12.1.0-2
ii libgnutls30 3.7.6-2
ii libjpeg62-turbo 1:2.1.2-1
ii libpam0g 1.4.0-13
ii libpixman-1-0 0.40.0-1
ii libstdc++6 12.1.0-2
ii libx11-6 2:1.7.5-1
ii libxdamage1 1:1.1.5-2
ii libxext6 2:1.3.4-1
ii libxfixes3 1:6.0.0-1
ii libxrandr2 2:1.5.2-2+b1
ii libxtst6 2:1.2.3-1.1
ii perl 5.34.0-5
ii tigervnc-common 1.12.0+dfsg-4
ii zlib1g 1:1.2.11.dfsg-4
Versions of packages tigervnc-scraping-server recommends:
pn tigervnc-tools <none>
Versions of packages tigervnc-scraping-server suggests:
ii openssl 3.0.4-2
-- no debconf information
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