Bug 834362

Summary:	Multi-seat broke in 3.4.x updated kernels, works in 3.3.x
Product:	[Fedora] Fedora	Reporter:	Scott Dowdle <dowdle>
Component:	kernel	Assignee:	Kernel Maintainer List <kernel-maint>
Status:	CLOSED DUPLICATE	QA Contact:	Fedora Extras Quality Assurance <extras-qa>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	17	CC:	gansalmon, itamar, jonathan, kernel-maint, madhu.chinakonda
Target Milestone:	---
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2012-06-21 20:26:37 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Scott Dowdle 2012-06-21 16:20:39 UTC

I'm not sure if this is the kernel or systemd or what... but I think it is the kernel.

I have one each of both of the Plugable multi-seat devices (UD-160-M and DC-125) using the new "multi-seat" feature in Fedora 17 with systemd, GDM, and GNOME.

Prior to updating everything was working great.  Since moving to the 3.4.x kernels (and I've tried .0, .2, and now .3) the desktop background comes up and it just sits there for about 5-10 minutes before the login screen appears.  At some point the main display dies but the multi-seats seem to work.

I saw this reported on one of the Plugable Kickstarter Updates (http://www.kickstarter.com/projects/1666707630/plugable-thin-client-the-50-computer/posts/247717).  I haven't tried reverting back to the 3.3.x kernel yet but will do that real soon.

I searched bugzilla to see if this was already reported but I couldn't find it.  Forgive me if this is a duplicate bug.

Comment 1 Scott Dowdle 2012-06-21 17:02:02 UTC

Just read a Google+ post from the Plugable guy regarding this:

https://groups.google.com/forum/?fromgroups#!topic/multiseat/siUkc4wrZBs

Quoting below:

- - - - -

Fedora 17 -- the first open source distro to have automatic USB multiseat -- shipped with Linux kernel 3.3.

Post-ship, Fedora 17 now offers a software update to kernel 3.4.0, which unfortunately causes problems: kernel panics are common and terminals often won't come up.  

Kernel 3.4.0 is the first to include a new driver for DisplayLink-based USB devices, called "udl".  Both "udl" (which is the new driver written by David Arlie to the DRM set of Linux graphics driver interfaces), and "udlfb" (which is the old driver written by us to the fbdev set of Linux graphics driver interfaces) are present in 3.4.0.  Unfortunately, udl is still maturing, and can cause kernel panics.

So to fix the issues you'll see with 3.4.0, we recommend disabling udl for the time being.  Udlfb is still present in the kernel, and will get matched against your hardware automatically, and plug and play multiseat will work again.  The easiest way to do this is to run the following commands and reboot:

echo "blacklist udl" | sudo tee --append /etc/modprobe.d/udlfb.conf

sudo depmod -a

And reboot.  One the server reboots, udlfb should match all USB graphics devices.  Please let us know if you have any trouble.

- - - - -

I haven't tried the work around yet but will soon... and report back.

Comment 2 Dave Jones 2012-06-21 20:26:37 UTC


*** This bug has been marked as a duplicate of bug 832188 ***