KUbuntu 9.04 hangs

Saturday, May 9. 2009

Dear Lazyweb,

what is the best way to debug a problem with the session DBus apparently getting stuck? The KDE4 session on this computer becomes completely unresponsive. An ssh login still works but a simple

export DISPLAY=:0
qdbus

doesn't return. No output at all.

qdbus --system

still works. Running

strace qdbus

shows it waiting on a read on some pipe it created right after reading /var/lib/dbus/machine-id.

ps aux showed two session busses running. One from the user and another one from root. The root session bus was probably created by running Adept a few minutes before.

strace on the dbus process of the user showed it polling and calling gettimeofday, apparently at timeouts. Attaching gdb to the session bus didn't give me any information

Anyway, I don't know enough about dbus and I would like to get rid of this annoying hang. Whatever you try to do with the computer, in the end you have to fall back to SysRq + {S, U, B} since nothing else can get the system back. Any ideas how to get more information on what could be the cause?

Posted by Matthias Kretz in Linux at 13:29 | Comments (15) | Trackbacks (0)

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is compositing enabled and do you have an intel card? then this is probably the same problem that i get. a workaround that works for me: disable compositing (and enable it again).

#1 roman on 2009-05-09 14:16 (Reply)

Strange, my old laptop with 855 Intel works but another machine with ATI also has this problem

#1.1 André Wöbbeking on 2009-05-09 14:32 (Reply)

And yes, disabling compositing worked for me too.

#1.1.1 André Wöbbeking on 2009-05-09 14:34 (Reply)

the cause is that its ubuntu!

haha, no, seriously, ubuntu sucks. its like the new windows ME. linux can be better than this, which makes me sad

thanks for reading this entirely unhelpful comment.

#2 peter.isles on 2009-05-09 14:51 (Reply)

Just to be safe, SysRq is not the best way to reboot a machine on which you can still remotely login. Instead do "sudo shutdown -r now".

But yeah, no idea about that dbus thing, sorry....

#3 Hans on 2009-05-09 16:17 (Reply)

I don't know much about dbus, but maybe try running it (qdbus) in gdb, to get a better idea of what/where it is failing/hanging?

#4 sandsmark (Homepage) on 2009-05-09 16:41 (Reply)

Compositing was disabled, old intel card (855). But I don't see how the graphics driver could be related to the problem. (Though the intel driver is a big problem in itself in its current form in (K)Ubuntu. On the 855 I switched it to XAA to not leave the system completely unusable. On my G35 I switched to UXA but it's still worse graphics performance than on the 855. XAA crashes right on startup with the G35.)

SysRq is the only way because a reboot from remote hangs the system even worse, so that the remote shell also hangs and it's hard power off or SysRq...

Other distribution probably needs to be tried.

#5 Matthias Kretz (Homepage) on 2009-05-09 16:42 (Reply)

> But I don't see how the graphics driver could be related to the problem.

I only wanted to say that I also had some kind of freeze. As I didn't have another computer to ssh I don't know the real reason yet. I only know that disabling compositing helped.

I updated my laptop to Sid's 2.7.0 Intel driver and switched to UXA, but I'm not happy yet. I probably also need a newer kernel for that.

#5.1 André Wöbbeking on 2009-05-09 17:37 (Reply)

According to the benchmarks posted on www.phoronix.com the latest intel drivers are performing badly whatever you do. XAA or older version (which probably uses XAA then) is apparently the only fast Intel atm (at least for 2D, OpenGL got a lot better for me with the latest intel).

#5.1.1 Matthias Kretz (Homepage) on 2009-05-09 19:55 (Reply)

When I use SysRq I do it using:

SysRq + R + E + I + S + U + B ---> To reboot
and
SysRq + R + E + I + S + U + O ---> To shutdown

More info: http://en.wikipedia.org/wiki/Magic_SysRq_key

Why you don't try to purge and reinstall dbus and some other related packages?

#6 User on 2009-05-09 19:02 (Reply)

same problem here I think. And another problem, I can't kill X server with "ctrl alt backspace" anymore (even when kubuntu isn't freezed)... strange
(nvidia btw)

#7 DanaKil on 2009-05-10 02:05 (Reply)

System Settings -> Display: Make sure to check 'Ctrl+Alt+Backspace restarts the xserver', click Apply/OK. This will install an application called 'dontzap' that will bring back this function to X.

You can also do it via command line.

First install the 'dontzap' package:

# sudo apt-get install dontzap

Once it is installed, disable it, which brings back the funtion you want:

# sudo dontzap -d

#7.1 nixternal (Homepage) on 2009-05-10 17:27 (Reply)

I will try that, thanks :o

#7.1.1 DanaKil on 2009-05-10 17:33 (Reply)

I have the same problem with kubuntu 9.04 for a long time. It makes the system a pain to use, as it becomes unresponsive very quickly.

#8 Nikos on 2009-05-10 04:01 (Reply)

Debian sid hangs to sometimes while in idle mode, but I think it is my wireless network which cause hang.

#9 OnlyWhisly) on 2009-05-10 15:58 (Reply)

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