!xcb_xlib_threads_sequence_lost error with GTK2 applications

[Ilya Kotov]

GTK2 applications randomly crash or freeze with error like:

[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.
<application>: ../../src/xcb_io.c:263: poll_for_event: Assertion `!xcb_xlib_threads_sequence_lost' failed.

where <application> is the name of the executable, e.g. audacious, soffice.bin, etc.

RELATED BUGS
LibreOffice: https://bugs.launchpad.net/ubuntu/+source/libreoffice/+bug/1801161
PCManFM: https://bugs.launchpad.net/ubuntu/+source/pcmanfm/+bug/1782984
Audacious: https://redmine.audacious-media-player.org/issues/798
FreeCAD: https://bugs.launchpad.net/ubuntu/+source/freecad/+bug/1754084
ClawsMail: https://www.thewildbeast.co.uk/claws-mail/bugzilla/show_bug.cgi?id=4203

OTHER APPLICATIONS
SpaceFM, Pidgin, GPicView and GIMP appear to have similar problems.

[Ilya Kotov (forkotov02)]

Same bug for libreoffice https://bugs.launchpad.net/ubuntu/+source/libreoffice/+bug/1801161

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[ԜаӀtеr Ⅼарсһуnѕkі (wxl)]

Related pcmanfm bug https://bugs.launchpad.net/ubuntu/+source/pcmanfm/+bug/1782984

[Alex Fedorov (fedorov-ao)]

Apparently, same bug for Audacious media player: https://redmine.audacious-media-player.org/issues/798 .

Also, Freecad users have encountered the similar error and managed to bypass is by setting LIBGL_DRI3_DISABLE environment variable to true before running Freecad: https://bugs.launchpad.net/ubuntu/+source/freecad/+bug/1754084/comments/13

[Alex Fedorov (fedorov-ao)]

Unfortunately, setting LIBGL_DRI3_DISABLE to true did not help to bypass the bug.

On the other hand, the bug does not manifest itself if there is only one active CPU core. The number of active CPU cores can be controlled by 'maxcpus' kernel parameter: add 'maxcpus=1' to GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub, then run update-grub as root.

[ԜаӀtеr Ⅼарсһуnѕkі (wxl)]

Looks like there's an upstream bug against Claws Mail, too:
https://www.thewildbeast.co.uk/claws-mail/bugzilla/show_bug.cgi?id=4203

[Peter S (guestsdfg)]

I have the same problem with eboard 1.1.3 on Debian Buster. The program build is quite old (2016), hence it seems that the problem is with some high-level library.

[John Sweeney (john-sweeney)]

I have the same problem with audacious, on UbuntuStudio 18.04

[Calmarius (david15b)]

Code::Blocks is affected too. I keep losing unsaved work.

[Tycho Kirchner (spawn-bugs)]

Apparently it's a bug in libx11, which persisted for a long time but
became much more likely with an update in libxcb.
Please see the still open merge request/patch at

https://gitlab.freedesktop.org/xorg/lib/libx11/-/merge_requests/34

Further reading:
This bug report (as it turned out now, it's probably *not*
a bug in gtk though):
https://gitlab.gnome.org/GNOME/gtk/-/issues/2767