Arch Linux

Rome

Member

Registered: 2011-05-29

Posts: 5

systemd-udevd stalls system

Hi all,

My system does weird things since one of the latest updates. All applications stall periodically, video playback pauses for half a second, audio dropouts, mouse hangs, keys are skipped etc.

I can't exactly tell which update caused it but I could narrow the problem down to the process 'systemd-udevd' that spikes massively in the system monitor at the same interval as the drop outs occur. When I kill the process everything runs like butter again and currently it seems like I'm not missing any functionality(?).

The problem is that I can't find what this daemon is used for and I especially can't find the place where it is started from.

My system:

CPU: Intel i7-2600k
RAM: 16 GB RAM
Mainboard: GigaByte GA-Z68AP-D3 (Intel Z68)
HD: Western Digital WD20EARX 2TB

I'm using the built in graphics of the CPU (Intel HD 3000), the monitor is attached via HDMI.

It's a fairly fresh and straight forward installation of arch x64 with gnome shell, gdm and a very  basic set of applications (firefox, thunderbird, wine). No wild experiments on this system.

The systemd package seems to be installed on my system but I have not installed it by myself (at least not on purpose). The system is still using the good old init and there are no processes running that have the name systemd in it (besides the process in question).

Does someone have an idea what is happening here?

tomegun

Developer

From: France

Registered: 2010-05-28

Posts: 661

Re: systemd-udevd stalls system

systemd-udevd is started in rc.sysinit and needs to be running to give your devices the correct permissions and set up some symlinks in /dev when you plugi-in/remove devices, and most importantly insert modules and firmware into the kernel on-demand.

My guess (but it is only a guess) is that some module is misbehaving when udev attempts to insert it. You could try increasing the logging level in /etc/udev/udev.conf to get more information in your logs. Hopefully it should tell you what is happening.

tomegun

Developer

From: France

Registered: 2010-05-28

Posts: 661

Re: systemd-udevd stalls system

Also, are you able to trace this back to a certain software upgrade? Most likely either "linux" or "systemd". Are you able to downgrade and check if the problem goes away so we can pin it down?

Rome

Member

Registered: 2011-05-29

Posts: 5

Re: systemd-udevd stalls system

Thanks for your response. I've restarted the daemon manually with  'killall systemd-udevd && /usr/lib/systemd/systemd-udevd --daemon' and it behaves correctly again, including hot plugging and without any spikes. But this helps only until the next reboot. I'll try to hunt it down further tomorrow, now it's time to go to bed.

Last edited by Rome (2012-09-01 00:25:26)

Rome

Member

Registered: 2011-05-29

Posts: 5

Re: systemd-udevd stalls system

Hmm, that didn't really help. I downgraded the kernel and most of my latest changes but no cigar here. It still spikes. I've raised the log level of udev to "debug" but this gave no clues either.

But I've observed something interesting. Every time a spike happens I get a new entry in Xorg.log:

[   254.546] (II) Quirked EDID physical size to 0x0 cm
[   254.546] (II) intel(0): EDID vendor "SAM", prod id 1574
[   254.547] (II) intel(0): Using hsync ranges from config file
[   254.547] (II) intel(0): Using vrefresh ranges from config file
[   254.547] (II) intel(0): Printing DDC gathered Modelines:
[   254.547] (II) intel(0): Modeline "1920x1080"x0.0  148.50  1920 2008 2052 2200  1080 1084 1089 1125 +hsync +vsync (67.5 kHz eP)
[...a lot of modelines...]
[   254.547] (II) intel(0): Modeline "2880x480"x0.0  108.00  2880 2944 3192 3432  480 489 495 525 -hsync -vsync (31.5 kHz e)

So it looks like my monitor gets detected over and over again. It's a Samsung SyncMaster P770HD connected via HDMI to the mainboard.

I usually have a custom kernel parameter (video=VGA-1:d) to turn off a phantom TV out that my mainboard introduces somewhere. I've tried to remove the parameter and surprisingly everything works fine again. The only drawback is that the system jumps several times between 1024x768 and 1920x1080 while booting up and the console is restricted to 1024x768.

I can live with that but it would be interesting to know what happens here.

Last edited by Rome (2012-09-02 19:43:04)