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Old 03-12-2016, 06:57 AM   #1
123user
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Registered: Feb 2016
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Strange freezes on my Ubuntu machine when running KDE programs (started recently)


I have this strange problem that appeared recently. I have been running a Kubuntu (15.10, Wily) box without problems for some time. But since a few days it has been horribly broken.

The other day, I installed the latest updates and rebooted the machine. But while logging in to the plasma (KDE) desktop afterwards, the progress bar stopped around 2/3 of the way through. Many reboots followed while I tried cleaning up my user account, but the progress bar would always stop at different points, sometimes early, sometimes late. I finally created a fresh user, but that one could not log in to plasma either. Then the KDE-related display (login) manager sddm started failing, too.

Switching to xfce and xdm everything works just fine! But sometimes when I launch KDE programs (under xfce) the Xorg process goes to 50% CPU and then spends most of its time in the "uninterruptible sleep" (D) state. What is going on?

If I stay away from anything KDE I don't have any problems. Some "light" KDE programs like Konsole and Konversation don't seem to be causing problems, while Gwenview and Okular often might.

I have tried looking in various logs for clues, but I have not spotted anything obvious. I have reinstalled many of the relevant packages.

What could possibly be wrong?
 
Old 03-12-2016, 06:09 PM   #2
Sigg3.net
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Since you already have a new/alternative desktop environment, have you tried to backup KDE settings and re-install kubuntu-desktop (or the equivalent)?

Also, please check your memory using memtest86+ (if you have >1 core force SMB and do round-robin CPU). I recently got faulty memory (16GB) in a computer I built, and got weird freezes until I decided to check out the RAM:P
 
Old 03-13-2016, 02:48 PM   #3
123user
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some more tests

So I made some more attempts to figure this out...

First, purging and reinstalling all of the "kde" packages did not make a difference. I had run memtest86+ before, but I did it again, this time pressing F2 to enable SMP mode, and --- part of the way through the test it froze. The red "+" at the top of the screen was still flashing, but the progress bars and the clock stopped. I have ECC memory, so I thought maybe that lots of errors were being generated and corrected, slowing down the test to a near stop? Anyway, I ripped out all of my RAM and inserted another couple of DIMM:s that I had lying around. I ran memtest86+ again, without errors.

I reinstalled all of kubuntu-desktop, convinced that the problem was solved, but no! SDDM loaded fine, but plasma still froze on me during login. So I thought maybe the problem was graphics-related. I have a Radeon card. I upgraded the graphics stack to the xorg-edgers version (this just bumped the version of the radeon and ati xorg driver packages). No difference. So I deleted the radeon and ati drivers instead, falling back, I suppose, to the VESA driver (the Xorg log output is a little hard to parse). Now I still got a long freeze at plasma login, but eventually it came through! But on some later login attempts the freeze remained, so that did not really solve it.

Summary so far: I got a freeze (not an error) once in memtest86+. The RAM has since been replaced. With VESA drivers I can sometimes log in to plasma, with Radeon drivers never. No program outside of the KDE suite has ever given me any problems, which I suppose would be a little bit strange if the problem were, say, a broken CPU?

Next I will run memtest86+ overnight, and try to get my hands on another graphics card. Any other ideas or insights?
 
Old 03-14-2016, 05:29 AM   #4
Sigg3.net
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Quote:
Originally Posted by 123user
With VESA drivers I can sometimes log in to plasma, with Radeon drivers never.
What is the model of the card? Have you tried loading the proprietary drivers (instead)?

Weird about that slowdown in memtest, but that could be ECC (I have never bought ECC RAM so I wouldn't know).

From a running system, can you please provide the output of dmesg?

Finally, do you use NFS at home (like a media server or something)? My machine regularly has 10 minute pauses unless I unmount and disable NFS shares in /etc/fstab. I know this can be mitigated by changing the NFS client timout settings.

Last edited by Sigg3.net; 03-14-2016 at 05:33 AM.
 
Old 03-14-2016, 05:36 PM   #5
123user
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Thank you for your help, Sigg3!

Since the last episode, I have tried the following:

Running memtest86+ for 24 hours (no errors).

Moving the graphics card to a different slot (did not help).

Switching the kwin compositor to XRender (did not help).

Replacing the graphics card with an nVidia card running the Nouveau driver -- works!

Installing the proprietary fglrx driver for my AMD card -- works!

I would not have thought about trying the proprietary driver if you had not suggested it. After all, I'm trying very hard to use free software here...

In other words -- it seems that I have isolated the problem to somewhere in the vicinity of the Radeon driver.

Also to answer your question: I don't run NFS, but I use zfs on the machine, and it runs a Samba server. I also notice that logging in to plasma does take quite a while even in the working configurations (I have tried waiting for hours in the non-working configurations though, so it is not just down to lack of patience).

The AMD card is a HD7750.

So what is the conclusion? Do I have a hardware fault or not? If there is a severe bug in the Radeon driver stack, how come I have not come across anybody else who is having this problem? Should I report it as a bug? If so -- what should I file it against? I have pretty much zero hard data in the form of log messages. I have been going over all the log files I could think of (.xsession-errors, syslog, dmesg, Xorg.0.log) and I have not spotted anything that I can definitely connect to this rather annoying problem.
 
Old 03-27-2016, 10:22 AM   #6
Sigg3.net
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Registered: Mar 2008
Location: Oslo, Norway
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You can post a bug report at the fglrx radeon driver mailing list, simply stating the same thing you did here (occasional freezes that is solved by running the proprietary driver instead). Hopefully that is enough for them to prompt further questioning or bug filing.

Nice that it works (even though you must use the proprietary driver). Consider marking the thread as [SOLVED] or [Sort of SOLVED] by editing the Title field of the initial post
 
  


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