Hello fellow Fedora users,
I've been using the same Fedora installation on my desktop for the last 4 years, but
for the first time I'm completely stumbled with a bug after upgrading from Fedora
Workstation 25 to 26.
When I press the slash/question-mark (on a PT-BR keyboard) key while focused into a
window, or when pressing backspace to erase that slash immediately afterwards, X11 will
freeze for about a second consuming 100% CPU. No other key causes the same behavior, not
even the slash key from the numeric keypad. I can observe the issue in GTK2, GTK3, Qt and
custom applications (such as Chrome and Firefox), but I cannot reproduce the behavior when
sending inputs to `xev` for observation. Even GDM is afflicted when typing my user
password, before ever having logged in.
Given the bizarre and extremely specific nature of the issue, my first suspects are
input-related software such as ibus, libinput or Xorg itself. Using different ibus
settings, and even attempting to disable it (by setting XMODIFIERS=@im=none) didn't
seem to have any effect. libinput doesn't seem like a good candidate, as raw events
captured by `xev` don't trigger the issue.
I profiled Xorg using `perf` but could not see any clues to what the problem is. I
generated a flame-graph [1] (source data at [2]), but most of the symbols seem to be
missing, probably courtesy of the NVIDIA proprietary driver.
I'm not even sure to which software to report this bug. Is anyone experiencing
anything similar, or has any suggestions for ways to debug to get to the core of the
problem?
[1]:
https://linux.ime.usp.br/~danielqm/f26-x11-perf/xorg.svg
[2]:
https://linux.ime.usp.br/~danielqm/f26-x11-perf/xorg.folded
--
Thanks in advance,
Daniel