Getting stuck while alt-tabbing

Mon Jun 21 05:35:09 BST 2004

On Monday, 21 Jun 2004 06:17, Daniel Klein wrote:
> Alexander Nordström wrote:
> > On Saturday, 19 Jun 2004 10:23, Daniel Klein wrote:
> > >I am using KDE 3.2.2 (distro is Debian / unstable) and I've had a very
> > >strange thing happen to me two times today already: While changing
> > >between tasks with alt+tab, I got stuck in the change tasks box.
> >
> > This is in the bugtracking system:
> > http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=254973
> >
> > and has been discussed in debian-kde:
> > http://lists.debian.org/debian-kde/2004/06/msg00137.html
> >
> > and in debian-user:
> > http://lists.debian.org/debian-user/2004/06/msg02534.html
> >
> > Those are all generally good places to look before asking.
>
> Thanks for the answers, but none of these seem to describe the problem I
> have encountered.

Okay, my apologies if I have made incorrect assumptions.

> To rephrase: I need to kill KDE, and the only way that is possible is by
> going for the 'start' menu / logout. Today the same thing happened to me
> again, unfortunately Kate decided to pop up a 'do you want to save'
> dialogbox which I could not answer in any way. I had to *HARDWARE RESET*
> my box. Do you know how icky that is, when you've gotten used to Linux?

That would indeed be quite unpleasant. I see you tried switching virtual 
terminals and killing X with Ctrl-Alt-Backspace, and it sounds like the lock 
keys are also unresponsive. Considering that, you may not have any luck with 
Ctrl-Alt-Del either.

Have you any way of logging into the computer remotely, such as SSH, assuming 
it would still respond to that? That is a much nicer way to kill a computer 
that has locked up, and in many cases, you need only kill the deviating 
processes. This might also allow further investigation of the problem.

Other than that, read 
http://www.tldp.org/HOWTO/Keyboard-and-Console-HOWTO-8.html#ss8.6 if you are 
not familiar with magic SysRq. It's important to know why it's good, why it's 
bad, and how you can use it to break toys. Then try the following, waiting a 
bit between each to let them take effect:

Alt-SysRq-K to kill all process on the active virtual terminal.
Alt-SysRq-E to send the TERM signal to all processes but init
Alt-SysRq-I to send the KILL signal to all processes but init
Alt-SysRq-L to send the KILL signal to all processes, including init
Alt-SysRq-S to run an emergency sync on all mounted filesystems to prevent 
data loss
Alt-SysRq-U to remount them as read-only to prevent data loss and stave off 
fsck on reboot
Alt-SysRq-R to turn off keyboard raw mode. This may let you use Ctrl-Alt-Del 
if it wasn't working before.
Alt-SysRq-B to force reboot
Alt-SysRq-O to force shutdown

These bypass regular keyboard handling, so there is a chance they might work, 
if they are enabled.

> I'm using Linux for stability.. this is pissing me off mightily.

That's understandable, but remember that we're all very lucky to be using 
something that is given to us.

> Question: What is metacity? (the bug you posted was dealing with
> metacity.. I don't feel like digging deep into googling and finding out
> exactly what it is. I'll assume it's a part of KDE?)

No need to dig deep: it's among the top results. It is a window manager -- not 
part of KDE, but some people will use that instead of a full-blown desktop 
environent like KDE.

As noted at the bottom, the problem doesn't really appear to be with metacity, 
but rather with the underlying X server:

"It's a xlibs bug with modifiers, downgrading xlibs to dfsg.1-4 is a good
workaround for the moment."

There are also instructions for how to do that on that page, if you think it 
might still help.

Here is the xlibs bug report: 
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=255192

Granted, that does indeed not sound too much like your problem on closer 
inspection, though you may get different results under different desktop 
environments and window managers. Anyway, the problem is Alt-Tab related, so 
this bug makes a good suspect.

> Why were these 
> things discussed on the DEBIAN lists and not on the KDE list? Why is
> that bug in the debian bug tracker and not in the KDE bugtracker?

     In fact, if you got the program that is giving you problems from a distro
     (as common today), it may be better to ask in the distro forum/list
     before trying the program's project forum/list. The project's hackers may
     just say, "use our build".
          -- http://www.catb.org/~esr/faqs/smart-questions.html#usefora

What ESR is getting at here is that Debian and other distributions make 
modifications that make their packages different from the upstream packages, 
and there is no easy way to tell where any problems were introduced. It is 
therefore more polite and efficient to deal with it at the latest instance of 
intervention. Obviously, the KDE developers cannot be responsible for 
problems introduced by the Debian team, should that be the case, and if it's 
not, it will be forwarded upstream.

Also, the graphical environment is a complex thing, and what may seem like a 
KDE problem is very often an X problem.

> RANDOMLY (I cannot provoke the behaviour at all), the taskchanger box
> will not close after I release alt-tab. This seems to be unrelated to
> whether I press and release quickly or not. After that, ALL keyboard
> input is ignored (none of the other descriptions you linked me to
> mention that - even alt becoming sticky wouldn't explain why numlock
> should no longer work), and all mouse clicking is ignored except for
> clicks on tasks in the change task box (clicking moves the frame, no
> selection or closing of the box happens) and clicks on the panel. By
> clicking on the panel, I can start tasks (konsole, konqueror...) but I
> won't be able to interact with the newly launched programs. I get to
> open the start menu and do the same there.

Just guessing here, but that sounds almost as though your kwin dies. That 
would have the symptoms of not responding to keyboard input, and window 
handling going south. It shouldn't prevent clicking on buttons or copying and 
pasting with the right-click context menu, though, so I am not sure. When 
it's happened to me, I have usually been able to re-run it by copying and 
pasting text from open windows into the Run Command dialogue or using that 
dialogue's history.

Again, I don't think it's a KDE problem -- it sounds much too severe for that. 
Without pointing too many fingers, the underlying X is more likely the 
culprit, and that may well give varying symptoms for the same problem under 
different desktop environments and window managers. I would still try 
downgrading Xlibs.

-- 
Alex Nordstrom
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