Re: F26: particular keystrokes cause Xorg to freeze momentarily, looking for debugging suggestions

[Daniel Miranda]

I never manually enabled compose keys, and slash does not seem to be working as 
such. But it does seem like the most likely explanation for the different 
behavior. I'll investigage that avenue further. Thank you Tim!
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Re: F26: particular keystrokes cause Xorg to freeze momentarily, looking for debugging suggestions

[Tim]

Allegedly, on or about 17 July 2017, Daniel Miranda sent:
> 
> 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. 

Has it been set as the compose key?

e.g. If you type /ae does it turn into: æ

Not that /that/ would explain the 100% CPU pinning, but could explain
why the slash is being treated differently from other keys.

-- 
[tim@localhost ~]$ uname -rsvp
Linux 3.9.10-100.fc17.x86_64 #1 SMP Sun Jul 14 01:31:27 UTC 2013 x86_64 
(always current details of the computer that I'm writing this email on)

Boilerplate:  All mail to my mailbox is automatically deleted, there is
no point trying to privately email me, I only get to see the messages
posted to the mailing list.

I'd just like to say that vinyl record crackles and pops are far less
annoying than digigigigital mu-u-u-u-usic hiccicicicups and
yooo-u tu-be ... pauses.


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Re: F26: particular keystrokes cause Xorg to freeze momentarily, looking for debugging suggestions

[Tim]

Going off on a tangent, but replying to this comment in the thread:

Allegedly, on or about 17 July 2017, stan sent:
> This sounds a lot like a vim plugin for editing html.  In that plugin,
> it uses the , as the key to indicate that it is receiving a command.
> So, whenever a comma is typed, it treats any character within a second
> as a command, and does a lookup to see if it should do anything.  This
> causes a pause whenever a , is typed if that plugin is active. 

I use some things added to the .vimrc file to do that kind of thing, but
its trigger character is the backslash:  \  The backslash is something
that we don't make a lot of use of in general typing, so about the only
time I'd ever type it in VIM was when using a special code.  On those
few occasions I do want to type it, I can either double-tap it, or just
wait a moment.

The comma, on the other hand, gets typed an awful lot, I always want it
to be a comma, and I don't want it interrupting normal typing.

So, if you can change your special code character, the backslash is a
reasonable one to pick, the comma seems a really bad choice.  And it can
be typed without having to use shift (at least on my keyboard layout),
so it's quick.

-- 
[tim@localhost ~]$ uname -rsvp
Linux 3.9.10-100.fc17.x86_64 #1 SMP Sun Jul 14 01:31:27 UTC 2013 x86_64 
(always current details of the computer that I'm writing this email on)

Boilerplate:  All mail to my mailbox is automatically deleted, there is
no point trying to privately email me, I only get to see the messages
posted to the mailing list.

Windows tablets are more like suppositories.


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Re: F26: particular keystrokes cause Xorg to freeze momentarily, looking for debugging suggestions

[Samuel Sieb]

On 07/16/2017 11:15 PM, Daniel Miranda wrote:

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?


I would suggest trying with a new user and see if that one has the same 
problem.  That will tell you if it's a user configuration issue or 
system-wide.

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Re: F26: particular keystrokes cause Xorg to freeze momentarily, looking for debugging suggestions

[stan]

On Tue, 18 Jul 2017 02:29:04 -
"Daniel Miranda"  wrote:

> The issue does not manifest itself in a VT.
> 
> I am definitely not using Wayland. The XDG_SESSION_TYPE env var is
> set to X11, and the GNOME doesn't have EGLStreams enabled to make
> Wayland work with the NVIDIA drivers.

So, definitely something to do with X processing.

> I will test a different DE and/or a live image whenever I have the
> time. I suspect I might not be able to reproduce the issue with the
> default settings, otherwise many other users would have complained
> already.

It sure seems likely.

> I seem to have quite a few new erros in journalctl compared to what I
> saw in F25 - many GTK assertions of different kinds, but none that I
> can correlate with the lagging keypresses.

I interpret that to mean that the behavior is not considered an
aberration, and so doesn't get logged.

> I did just notice that the systemd user sessions is acting in a
> strange manner. it seems to always be dying when I log out from
> GNOME, even when lingering is enabled and/or I have a second session
> running. I can't easily find what is causing it to die, other than it
> doesn't seem like a crash (`journalctl --user` indicates it was
> killed by SIGRTMIN+24, which seems just like the systemd-exit.service
> unit being called normally).

Can't help with this, my systemd fu is weak.

I had a look in bugzilla, and didn't find anything about this,
though it would be easy to miss depending on what it was reported
against.  I'm out of ideas. Maybe someone else can come up with an
explanation. And if I think of anything else, I'll let you know.
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Re: F26: particular keystrokes cause Xorg to freeze momentarily, looking for debugging suggestions

[Daniel Miranda]

The issue does not manifest itself in a VT.

I am definitely not using Wayland. The XDG_SESSION_TYPE env var is set to X11, 
and the GNOME doesn't have EGLStreams enabled to make Wayland work with the 
NVIDIA drivers.

I will test a different DE and/or a live image whenever I have the time. I 
suspect I might not be able to reproduce the issue with the default settings, 
otherwise many other users would have complained already.

I seem to have quite a few new erros in journalctl compared to what I saw in 
F25 - many GTK assertions of different kinds, but none that I can correlate 
with the lagging keypresses.

I did just notice that the systemd user sessions is acting in a strange manner. 
it seems to always be dying when I log out from GNOME, even when lingering is 
enabled and/or I have a second session running. I can't easily find what is 
causing it to die, other than it doesn't seem like a crash (`journalctl --user` 
indicates it was killed by SIGRTMIN+24, which seems just like the 
systemd-exit.service unit being called normally).
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Re: F26: particular keystrokes cause Xorg to freeze momentarily, looking for debugging suggestions

[stan]

On Tue, 18 Jul 2017 01:43:45 -
"Daniel Miranda"  wrote:

> Either way, the fact that I can observe the issue even in GDM makes
> me suspect something of the core stack (X11, GNOME, ibus, etc) is the
> culprit. I might have to resort to scavenging the changelogs/commits
> of some of them between F25 and F26 to see if something stands out.
> But it would seem reasonable that more people would report similar
> troubles if it was something that did not depend on my specific
> combination of configurations and versions.

What if you go to a virtual console, Ctrl-Alt-F2, and login.  Does the
issue occur with typing in the console?  The consoles use a different
keytable than X, though it is derived from the X keytables.  If it
doesn't occur there, then that really points to the graphical interface.

Is it possible that you were formerly using X, and are now using
Wayland?  Or vice versa?  Switch and see what happens.

You could also try one of the other desktops (KDE, cinnamon, xfce,
mate, lxde) and see if the problem occurs when using it.

Try looking in journalctl -b to see if something strange is happening
at boot.  And type journalctl -f to tail the journal, then trigger the
behavior to see if something shows up in the logs.
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Re: F26: particular keystrokes cause Xorg to freeze momentarily, looking for debugging suggestions

[Daniel Miranda]

Thank you very much for your help stan! 

I do not have any such software AFAIK. I even tried *enabling* ibus typing 
booster (which I did not previously had enabled), and it changed nothing.

Either way, the fact that I can observe the issue even in GDM makes me suspect 
something of the core stack (X11, GNOME, ibus, etc) is the culprit.
I might have to resort to scavenging the changelogs/commits of some of them 
between F25 and F26 to see if something stands out. But it would seem 
reasonable that more people would report similar troubles if it was something 
that did not depend on my specific combination of configurations and versions.
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Re: F26: particular keystrokes cause Xorg to freeze momentarily, looking for debugging suggestions

[stan]

On Mon, 17 Jul 2017 06:15:37 -
"Daniel Miranda"  wrote:

> 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.

This sounds a lot like a vim plugin for editing html.  In that plugin,
it uses the , as the key to indicate that it is receiving a command.
So, whenever a comma is typed, it treats any character within a second
as a command, and does a lookup to see if it should do anything.  This
causes a pause whenever a , is typed if that plugin is active.

The fact that xev isn't affected by this suggests some type of macro in
the key interpretation chain, as I think that xev gets raw keycodes
directly from the kernel.  Do you have any kind of desktop assistant
that would create macros installed?  Something that would monitor all
your keystrokes, looking for shortcuts that would do things for you.

I checked the keymappings in /usr/share/X11/xkb/symbols/pt, but it
inherits the slash from latin(type4), and I couldn't find that.  That
is unlikely to be the cause.
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F26: particular keystrokes cause Xorg to freeze momentarily, looking for debugging suggestions

[Daniel Miranda]

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

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